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Chapter 5. Shelter and productivity, health & welfare of livestock Introduction A brief summary is presented below of general shelter effects that might result from trees placed in the landscape for benefits of shelter, biodiversity and recharge control. Effects of shelter on windspeed Shelter can substantially reduce windspeed on the farm. The degree and distribution of shelter depends mainly on the height, structure and position of the windbreak (Bird et al. 1996; Bird 1998; Caborn 1957; Cleugh & Hughes 2002; RIRDC 1997a,b,c; Sturrock 1969, 1972). Thus, the width of paddock that is protected is largely determined by the height of the windbreak, while the degree of protection at certain parts of this shelter zone is influenced to some extent by the porosity of the belt. The area close to a dense belt has a very high degree of wind reduction, while a more permeable belt has the best protection several windbreak heights away, although this may still be less than the maximum obtained within one height of a dense belt (Bird 1998; Bird et al. 1996). Ideally, a grid of belts will give the best protection because the wind does not blow consistently from one direction (see Bird et al. 2002a) and therefore cannot be blocked with a single windbreak. Shelter effects on plant growth There are positive and negative impacts of windbreaks, as shown in Figure 1 (after Bates 1911).

-1 0 -8 -6 -4 -2 0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0

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ure

yiel

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Shelter can increase agricultural production (Bates 1911; Marshall 1967; Bird et al. 1984, 1992, 2002a, 2002b; Radcliffe 1985; Kort 1988; Reid & Bird 1990; Nuberg 1998), mainly by altering the microclimate in the sheltered area, and from reducing the direct effects of wind on plants (Grace 1988; Cleugh et al. 1998; Nuberg 1998). The most spectacular example of an animal response to shelter in Australia has been at Armidale, where Lynch and Donnelly (1980) found that wool production in well-stocked plots partially sheltered by a 1 m high iron fence was 43% greater than in open plots. This was due to a combination of direct sheltering of the sheep and increased pasture growth. There has been no research reported elsewhere in Australia to confirm that magnitude of response to shelter – the recent research from the RIRDC-funded National Windbreaks Program has indicated only small effects on pasture and crop growth (see Special Issue of Australian Journal of Experimental Agriculture 2002, Volume 42).

open field yield

GAIN - less evapotranspiration - less physical damage - temperature modification

East field

LOSS - shading - root competition - interception of rain

distance from windbreak (tree heights, H)

open field yield

Belt

West field

Figure 1 Generalised representation of possible shelter effects on plant growth, indicating factors that influence losses in the competitive zone and gains in the shelter zone.

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The most substantial effect of shelter on the pasture plant is probably to reduce abrasion by wind, and to reduce transpiration from the plant or evaporation of water from the ground surface. However, evaporation is dependent upon a complex relationship between wind speed and leaf (or soil) surface temperature, which is modified by the plant’s ability to limit transpiration by stomatal closure, so shelter does not always reduce plant water loss (Bird 1998; Cleugh 1998). Similarly, while shelter reduced the loss of water from soil in the late spring by 10 mm (Lynch et al. 1980), this can only occur at times when the topsoil is damp, including periods of a few days after autumn rain (Bird 1998). Sixty percent more pasture was grown in the sheltered zone (3-5H from the belt, where H = tree height) than in the open on the Canterbury Plains in New Zealand (Radcliffe 1985). Recent data from Melville Forest in Victoria indicate a much smaller response, around 10% gain in the sheltered zone (2-10H) when a synthetic mesh windbreak surrounded the plots. However, the annual livestock carrying capacity of the farm was probably improved by a greater percentage because much of the increased pasture growth came in the early winter period, a time of scarcity (Bird et al. 2002b). No consistent effects of shelter on pasture production were seen when single shelterbelts of trees were examined, apart from a depression in yield of around 30% in the zone to 1H (Bird et al. 2002a). These results are similar to those of Hawke and Tombleson (1993), Hawke & Gillingham (1996) and Hawke et al. (1999) in NZ, and indicate that gains in overall pasture growth are unlikely to be large. The major gains in animal performance may be from relieved stress on the animals and a greater amount of pasture produced in winter. An extra 3 kg/ha of pasture dry matter produced daily in winter is not large, but compared with unsheltered amounts of 7-14 kg/day (Bird et al. 20002), it provides a significant percentage increase in pasture during this period of scarcity. It could support an extra 1-2 sheep/ha, at a time when these animals must either rely on dry residues from the previous year or be fed supplements of hay or grain. Shelterbelts can increase crop yields, even allowing for the cropland lost from the paddock and the narrow zone of competition near the belt (Bird et al. 1992). Sturrock (1981) found a 35% increase in oat yield in the very windy Canterbury NZ environment. Australian results include increases of 22% for oats and 47% for wheat in the sheltered zone 1-15H from the windbreaks at Rutherglen Vic., and 30% for lupins at Esperance WA (Bird et al. 1992). However, other recent responses have not been as positive (Nuberg 1998; Nuberg et al. 2002; Sudmeyer & Scott 2002b). The cropping studies were conducted in areas having over 600 mm/annum of rain and it is possible that a different response to shelter might be obtained in lower rainfall areas or years. Studies to measure yield at varying distances from shelterbelts, using small-plot harvesters in WA (Sudmeyer et al. 2002), or GIS-linked yield-mapping technology on headers in SA (Bennell 2002), indicate that there are sites and seasonal conditions where shelter does improve yield. If narrow belts (3-row, 10 m wide) of mature height 20 m were placed in a grid, with sides about 250 m apart (10 H), 7.8% of the land would be fenced to trees. This is not useable for agriculture, and there is a reduced yield in the zone near the belt (0-2H, the severity depending on tree species), but the yield in the actual grazed or cropped ally area could be increased by 10-20% to off-set the losses. Shelterbelts may shade pasture. This may be a particular problem in winter with dense belts oriented east-west, for such belts cast long shadows on the southern side of the belt for most of the day. Grazing stock target pasture that has a higher water-soluble carbohydrate content – and that is found in unshaded areas (Ciavarella et al. 2000). An observable consequence is that pasture in the winter-shaded areas may become rank and there may be a dominance of species such as capeweed (Arctotheca calendula) and thistles. Shading may also, on clay soils, result in bare ground as a result of pugging, because the soil surface tends to remain damper there than in open parts of the paddock. Shelter reduces topsoil loss The role of shelter in reducing wind erosion is not well known, although it can substantially reduce soil less in cropping areas (Sudmeyer & Scott 2002a). Long-term sustainability is affected by removal of topsoil dust at times when our conservation tillage and other methods fail. The clay and silt particles in dust contain most of the soil nutrients and organic matter. Intensive grazing systems may also predispose soils to wind erosion in the autumn and precautions must be taken. A net of belts will alleviate much of the danger because wind erosion is proportional to the cube of wind speed; reducing paddock wind speed by half will reduce wind erosion to one-eighth and safeguard loamy or sandy soil (Bird et al. 1992). Agronomic prescriptions alone are not effective over the entire range of risk conditions. Lost topsoil is virtually irreplaceable because the rate of soil formation is so slow.

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A drought in 1982 in southern Victoria was due to a shortage of rain from July to November inclusive (rainfall at Hamilton was 159 mm compared with the long-term mean of 369 mm) and there was a resulting shortage of pasture growth in that spring. This led to extensive wind erosion during the late summer of 1983. Failure to remove sheep from the paddocks early in summer left the soil in an erodible state. At Glenthompson, where windbreaks were present the damage was reduced, but sand was deposited to windward and through the belts. There were too few belts to prevent the windspeed from recovering in the intervening space. Shelter reduces animal stress Shelter reduces the amount of energy required to maintain an animal, providing more energy for production (Bird 1984; Bird et al. 1984; Reid & Bird 1990). With shorn sheep, shelter that reduces windspeed by 50% can reduce energy losses by 20% (Black & Bottomley 1980). Even with 3 cm of wool, persistent strong wind can reduce gains in liveweight or wool production. Shelter that can cut such winds by 50% can increase liveweight gain by 30%. Cattle are resistant to cold, but when wind and rain reduce the insulation of the coat their heat production is increased. The efficiency of production (liveweight gain or milk output per unit of feed) is improved by shelter. High humidity and temperature also affect cattle – shade alleviates the stress and improves milk production and weight gain (Bird 1984; Reid & Bird 1990). Shelter reduces livestock losses Shelter reduces deaths of newborn lambs. The average of all trials in SE Australia show that effective shelter reduces these losses by 50% (Bird et al. 1984). Wind is the major problem but losses are greatest when accompanied by low temperature and rain. Without shelter, all lambs born on such severe days may die (Donnelly 1984; Obst & Ellis 1977). Shelter reduces losses of exposed shorn sheep – those less than two weeks off-shears are susceptible. On the 7/12/82, 21-22/3/83 and 1/12/87, over 250,000 sheep died from exposure in SW Victoria (Bird & Cayley 1991). Some farmers lost over 1,000 sheep. Losses were minor where sheep had access to shelter. The presence of strategically placed woodlots on a property provides an insurance against such losses. The whole farm situation Modelling studies indicate that with 10% of a farm planted in windbreaks, reducing wind speed over the farm by 33-50%, the farm may be more productive and profitable in the long term (Bird 1991; Bird et al. 1996). Greater gains in livestock productivity may result from the increased supply of pasture and reduced environmental stress. These gains on the sheltered land may offset the loss on land occupied by trees. The long-term development of 30% of the total farm area in shelter/timberbelts and woodlots can produce a more environmentally sustainable land use, as a result of reduced salinity and erosion (Raper 1998), without severely affecting farm income. Moreover, experience has shown that the remaining land on large properties is better managed and fertilized, so that productivity on the farm may actually increase. (This can also happen simply because, for various reason, some areas of the property are unresponsive in that they produce less than the cost of inputs of fertiliser, fuel and management expended). High fertility grazed pasture systems now provide the opportunity to diversify production on a substantial portion of the property (Cayley et al. 1999).

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Shade & shelter benefits for dairy production – review of literature 1972-2002 Effects on pasture, animal health and welfare With respect to animal production, the main issues associated with providing shelter are:

• Direct effects on pasture production and composition (positive and negative) • Direct effects on animal production and welfare (shade, shelter from cold/wet/windy weather) • Indirect effects on health (pests, diseases) • Possibility of using tree/shrubs as browse of fodder

Provision of shelter belts There is ample information available on the design and establishment of shelterbelts and timberbelts (Bird 1998; Bird et al. 1996, Bird 2000). However, apart from cypress and some pine belts, and some areas of intact roadside vegetation, there are few good example of shelterbelts in the dairy areas. The cypress are all of the multi-stemmed, wide-branching variety and poor examples of a good belt height or structure. There is a need to promote the establishment of effective narrow belts that provide good height and density, without encroaching over the paddock or casting too dense a shade in winter. Shading in winter encourages the growth of capeweed and other less desirable pasture species, at the expense of the sown species. From the perspective of biodiversity, narrow belts are not very effective but, if fenced and containing some native species, would provide habitat for many species of birds. Narrow, managed timberbelts (Chapter 6) would provide an additional financial return as well as providing shade, shelter, habitat and control of deep drainage and nutrient leakage (Chapter 3). Trees could also be established along riparian zones, where fencing must be done anyway to exclude stock, to provide shade and shelter and other services. Shelter effects on pasture We have not been able to demonstrate substantial benefits of shelter on pasture growth. We found that comprehensive shelter from artificial mesh (enclosures 10 m x 10 m) did improve plant growth by 10%, with most of the benefit occurring in early winter when it would be most needed (Bird et al. 2002a,b).. What evidence there is suggests that gains in the sheltered zone are matched by an equivalent reduction in the competitive zone (the area adjacent to a windbreak where trees and pastures or crops compete for light, nutrients or water). The loss of production from the land taken up by the trees would possibly result in a net loss of pasture grown from the overall area of land. However, this loss could be more than offset by the modified microclimate and reduced stress to the stock, resulting in lower maintenance energy expenditure. Other benefits from the trees and shrubs might occur from improved biodiversity, improved control of nutrient leakage and possibly recharge control. If there was a farm forestry element built into the system that would also produce long-term benefits. Murayama et al. (1978) investigated the effects of 0, 60 or 80% shading on the growth and chemical composition of lucerne. Leaf number, leaf area, dry weight and total N and total available carbohydrate yield decreased with increased shading. Top:root ratio was increased. Shading increased growth rate during the vegetative stage and the increase was more marked after 1st flowering. Windbreaks have, however, been found to improve the growth of lucerne by reducing wind stress (Peri & Bloomberg 2002). Where pastures are irrigated there may be substantial savings in water where the environment is windy. Research at Lincoln University, NZ, has shown a substantial effect of pine/cypress timberbelts on increasing the water reaching the ground when spray equipment is used. In very hot environments there may be additional effects of reduced windspeed on the plants themselves. There are a number of disadvantages of shelterbelts, many of which have already been presented. Many of the disadvantages can be minimised by appropriate management or design.

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Gregory (1995) lists the disadvantages of shelterbelts as:

• loss of grazing area • reduced pasture growth near the belt • costs of fencing and shelterbelt maintenance • compaction/pugging near belts that are too dense and encourage cattle to congregate close by • fertility transfer within the field where belts are too dense – resulting in an accumulation of

nutrients in the stock camps close to the belt • slower removal of excess surface moisture from the soil – a problem along muddy laneways in

winter time, particularly when shaded • disruption of drains by tree roots • stock poisoning – a potential problem with some species (e.g. cypress, pine, sugar gum) • providing a harbour for pests and pathogens

Health and welfare of livestock Providing shelter and moving stock to adequate shelter is a moral responsibility which is implicit in the ‘five freedoms’ described by the Animal Welfare Advisory Committee of New Zealand, and in general it is difficult to argue that it is a responsibility which either imposes unreasonable costs or is unrealistic to achieve (Gregory 1995). Health concerns of providing shelter include cypress toxicity, a harbour or vector for disease and pests (badgers, ferrets, ticks, etc.) – see also Biodiversity section. Macrocarpa cypress is the most important conifer that can lead to abortions in New Zealand but P. radiata needles can lead to abortion in cows two months or more pregnant (Knowles & Dewes 1980). The compound responsible in both cases may be isocupressic acid (Gardner et al. 1994), although high levels are not always present. Eucalyptus cladocalyx (sugar gum) leaves are also known to cause death from cyanide poisoning when sheep and goats get access to wilting foliage, but there do not appear to be reports of cattle being affected.

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Heat stress in dairy cattle Animals gain heat primarily through metabolic activity. On hot days the animal must offset the extra input from the environment - mostly from radiant heat – by increased heat loss from the body and/or by reducing metabolic heat production. The latter is accomplished by reducing intake and eliminating unnecessary exercise. Heat is dissipated from the body through convection, conduction, radiation and evaporation. With extreme heat, the animal attempts to increase heat loss by panting and sweating, thereby increasing evaporative losses. All efforts to maintain homeothermy demand energy – and that can be at the expense of growth or lactation. The thermoneutral zone (comfort zone) has lower and higher critical air temperatures, between which the animal is not under stress and where the maintenance energy needs are relatively constant and low. The temperature range and ability of the animal to balance heat losses and gains depends on species, genetic constitution, size, health, age, energy reserves, coat condition, and whether pregnant or lactating. On average, cows have a range of about 16ºC, calves 12ºC, adult sheep 23ºC and lambs 1ºC (Bianca 1968). Heat stress causes a decrease in voluntary feed intake and milk production in dairy cows. The net energy requirements of dry cows for maintenance were almost constant at 18°, 27° and 32°C and tended to increase by about 5% at 36°. However the metabolizable energy (ME) requirements of dry cows given roughages for maintenance started to increase at lower environmental temperatures than 32°C. This increase is affected by the type of roughage given, due to the difference in heat increment among roughages. The energy requirements of lactating cows increased at high environmental temperatures, due to the increase in the ME requirements for maintenance (Kurihara 1992). Milk production in unshaded dairy cattle is depressed by high temperature and radiant heat loads, particularly when there is little wind to dissipate body heat. A breeze accelerates the rate of convection, but convection is increased only as the square root of the wind velocity. Thus, quadrupling the windspeed only doubles the convectional loss. Conduction is reduced by the insulative properties of the skin covering (still air being a poor conductor) and by subcutaneous fat (Johnson 1965).

Shade does not change the relative humidity (RH) nor greatly affect the air temperature – it reduces the radiation load of the animal (Johnson 1965). The effect of shade on animal welfare and production will depend on the air temperature, humidity and wind. I have adapted Figure 2 from a table in Johnson (1965) where the RH is kept constant – it shows clearly that radiation will augment the decline in milk production when the air is hot. Figure 2 shows also that Holstein cows appear to be more susceptible than Jersey cows. The implication of providing shade is that it would reduce the level of radiation and increase milk production.

Figure 2. Effect of radiation and temperature on milk production of Holstein and Jersey cows (adapted from Johnson 1965)

0

20

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60

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0 100 200 300 400 500 600 700

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7deg C, Holstein7 deg C, Jersey21 deg C, Holstein21 deg C, Jersey27 deg C, Holstein27 deg C, Jersey

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However, the situation is not that simple because air temperature is not the only factor affecting milk production. Humidity above 70% will severely depress milk production because it reduces evaporative cooling, even when air temperature is moderate (85°F). A temperature-humidity index (THI) was developed for lactating Holstein cattle in climate chambers:

THI = 0.55 Dry Bulb T + 0.2 Dewpoint T + 17.5 A decline in milk production was apparent for THI >76. At higher THI the more productive cows were affected more than were poorer producers. Igono et al. (1992) investigated the environmental profile of a desert climate in central Arizona. Overall, milk production is lower during heat stress compared with thermoneutral periods. During heat stress, the cool period of hours per day with temperature less than 21°C provides a margin of safety to reduce the effects of heat stress on decreased milk production. Using minimum, mean and maximum ambient temperature, the upper critical temperatures for milk production are 21°, 27° and 32°C, respectively. Using THI as the thermal environment indicator, the critical values for minimum, mean and maximum THI are 64°, 72° and 76°C, respectively. Sleutjes et al. (1991) tested 3 indices of heat stress for cows in Brazil: Black Globe Humidity Index (BGHI); Temperature Humidity Index (THI); and Thermal Radiation Index (TRI). According to the BGHI index, an open-air stable was found to be extremely uncomfortable for animals on hot summer days. Shade, especially ventilated shade, had a BGHI of 81-82, indicating that with proper management European cattle may withstand the tropical summer and remain productive. According to the THI index, none of the housing types (barn, asbestos roofed shed, tree shaded pad or unshaded pad) offered any comfort (THI = 81.8); however, the index does not take radiation and ventilation into account and the authors do not recommend it for determining the microclimate. Heat stress in controlled environment rooms reduced feed intake, nitrogen retention and liveweight gain more in Friesian than in Brahman cattle (Kellaway & Colditz 1975). Heat affected liveweight gains of feedlot cattle in Arizona (Ames & Ray 1983) and in Louisiana the differences in daily gains of cows and calves grazing with or without shade were 0.6 and 0.3 kg, respectively (McDaniel & Roark 1956). Effects of shade were also recorded in California by Garrett et al. (1960) and in Kansas by McIlvain & Shoop (1971). However, others reported no gains due to shade (Johnson 1965). The distribution of shade is important as cattle can continue grazing whilst shaded; shade from artificial structures is not always effective (Arnold & Dudzinski 1978), especially when it restricts airflow and loss of radiant heat. The intake and apparent absorption of major mineral and trace elements in lactating cows are depressed by heat stress and it is likely that the mineral requirements for calcium, phosphorus, magnesium and sodium in lactating cows increase under high temperature conditions (temperature above 27°C) (Kume 1992). In North America, providing shelter to beef feedlots in the winter improved growth rates without affecting feed conversion efficiency (Hoffman & Self 1970). The main function of shade is to decrease the heat load by reducing incident solar radiation. Studies with grazing beef cattle have shown that the cows body temperature and use of shade during lactation were correlated with calf birth weight and growth rate to weaning (Bennett & Holmes1987). Roman-Ponce et al. (1977) showed effects of heat stress on milk yield and conception in Florida. Black globe temperatures of 28.4°C from shade (an insulated metal roof) and 36.7°C for no shade prevailed over 2 summers. Shade improved milk yield by 10.7% and improved conception rates from 25.3 to 44.4%. Heat stress in the last 60 days of gestation adversely affects dairy production in the following lactation in tropical and sub-tropical climates (e.g. Moore et al. 1992). Production is improved in the tropics by providing tree shade (Macfarlane & Stevens1972). Ugarte & Dominguez (1977) compared free grazing with artificial shade and control grazing with natural shade in Cuba and found that milk production was higher under natural shade.

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Provision of shade has improved milk production in Argentina (Valtorta et al. 1996), South Africa (Muller et al. 1994), Brazil (Carvalho et al. (1993), Turkoman SSR (Kelov & Kolesov 1974), Cuba (Sanchez & Febles 1999) – and see other reference abstracts for other examples. Hot weather in areas with relatively moderate climates also causes heat stress, with resultant decrease in milk production (Armstrong 1994). Korsun (1993) provided a shaded area for feeding Russian Black Pied cows during hot summer conditions in the Ukraine. Feed consumption decreased for all cows when air temperatures were >24°C, water consumption increased and time spent ruminating decreased. Feed intake was on average 9% higher than for cows without shade, and the level of aggressive behaviour was 32-38% lower. Milk yields were on average 5.2% higher than those of cows kept without shade. Muller et al. (1994) found that shaded Friesian cows in a Mediterranean climate in South Africa had greater feed intake, less water consumption, overall milk yield was 55% higher but no difference was found in milk composition of shade vs. no-shade cows. At prevailing prices and costs the improvement in milk yield resulted in a net return of 42% per annum on the capital outlay of the shade structure. Francos & Mayer (1981) examined the fertility of cows in dairy herds in the northern part of Israel in 1979. In 28 herds the fertility depression during the hot summer months was slight but in another 21 herds the depression was greater. They suggested that a good fertility status of a herd is associated with a better ability to withstand thermal stress, probably due to favourable conditions of husbandry. Marschang (1972) observed that, for milk production, it was disadvantageous for cows to calve during the summer or early autumn as heat stress in late pregnancy caused them to be poorly prepared for their next lactation. Marschang & Schlauch (1973) found a relationship between environmental temperature and reproduction, with the poorest conception rates to AI being obtained in the two hottest months. Heat stress inhibited foetal development at all stages of pregnancy but particularly the last stage. Thompson et al. (1996) studied infertility in Texas Holstein dairy cattle and found that the strong seasonal decrease in pregnancy was less severe on farms that provided shade in the lounging, holding pen and dry cow areas. Collier et al. (1979) estimated that the effect of shade in the last third of pregnancy on subsequent milk yield was 2805± 136 compared with 2612± 136 kg for no shade. The no-shade treatment also reduced birth wt. of calves. Neuworth et al. (1979) examined the effect of successive exposure of 3-4-week-old male 8 Holstein calves to 5 temperature levels ranging from 15.5°C to 37.7°C at 60% RH on stroke volume, heart rate, arterial systolic and diastolic pressures, plasma cortisol and thyroxine levels and internal and skin temperatures. The calves responded to acute heat stress only above 32.2° C at 60% RH and did not demonstrate a marked attempt to acclimatize until at least 4-5 hours of exposure at 37.7°C. Australian and New Zealand studies Gregory (1995) contended that providing shelter in New Zealand from the sun in hot conditions improved milk yield and milk fat yield, while reducing mastitis and increasing conception rates in dairy cattle and growth rates in fattening cattle. Effects on milk yield are more related to THI than to temperature alone. High-performing herds are more susceptible to a rise in THI. Gaughan et al. (1998) found in SE Queensland that for Holstein cows under natural conditions, cows did not seek shade when the temperatures were <30°C. As ambient temperature, solar radiation and relative humidity increased, respiration rate increased. Cows with a high percentage of black coat preferred shade, while those with a high percentage of white coat did not seek shade. Goodwin et al. (1997) provide another account of this experiment with shade type selection by Holstein-Friesian dairy cows provided with different types of shade (galvanized iron roof 3 m high, Sechium edule (choko) vines on a 3 m high trellis, 80% shade cloth on a 3 m high frame, and natural shade trees). An unshaded area was also provided. Cows selected the galvanised iron roof most frequently when temperatures rose above 30°C, with no significant differences between other shade types. Heat stress is a key limitation to productivity during summer and autumn in Northern Australia, with Holstein-Friesian cows not grazing between morning and afternoon milking once daily maximum temperature exceeds 30°C (Cowan et al. 1995).

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Dragovich (1978) examined daily milk yields at 3 dairy farms having some irrigated feed and located in a semi-arid climate in New South Wales, for a 2-yr period. No significant differences were observed between production on hot days (>27°C) and other days, nor between production on days having varying heat intensities above the 27°C threshold. Neither prolonged periods of high temperature nor the rapid onset of hot weather resulted in consistent declines in farm production. Feed of adequate quality and quantity, and acclimatisation of cows to temperatures that were often not greatly above the 27°C threshold, probably contributed to the lack of a significant decline in production in association with high temperature. Mayer et al. (1999) have looked at the situation for the 15 major dairy regions in Australia, constructing a model to estimate production losses due to high THI. An integrated package for 200 locations is available on CD from Dairy Research and Development Corporation or from Australian Tropical Dairy Institute on http://www.dpi.qld.gov.au/atdi/). Managers are then able to look at historic climate patterns and estimate the economic cost/benefit of various strategies to alleviate heat stress, including provision of shade with or without sprinklers at the dairy. The THI model used daily maximum temperatures with humidity at 1500h, which was a better predictor of milk production losses than daily average THI. The meteorological data is that of the Australian Bureau of Meteorology. Dairy production data records were obtained from various research stations, district factory records and on-farm records in Queensland and northern NSW over a number of years, for spring-summer periods. The THI index was calculated as:

THI = temperature (°C) + 0.36 dew-point temperature (°C) + 41.2 The results of the Mayer et al. (1999) survey were as follows:

• The milk production patterns varied among sites, but all showed a general decline as THI increased beyond a certain point.

• The point at which production declined was higher in the tropical and subtropical studies, indicating better adaptation to heat.

• Losses were also greater for herds with above average production levels. Herds with low producing cows showed little effect of heat, even at THI up to 87.

• Applied management - shading and sprinklers – had a THI threshold of 83, about 2 units higher than for similar cows under average conditions.

• Milk fat and protein relationships behaved similarly to milk production. • Reproductive performance was also affected as THI increased, with lower first service

conception rates, more days open and a larger number of services per pregnancy. It is worth noting that Sleutjes et al. (1991) considered that the THI does not take radiation and ventilation into account and they do not recommend it for determining the microclimate. They found that a Black Globe Humidity Index (BGHI) did account for shading effects in reducing radiation. BGHI would probably be a better predictor than THI for Australia, but presumably it would not be possible to get detailed records for use. Cold stress in dairy cattle Prolonged cold stress causes reduction on productive processes such as growth and lactation, due to diversion of energy towards the maintenance of homeothermy (Ames & Ray 1983). Intake may increase but the maintenance requirement of energy may exceed the intake of digestible energy and, unless body reserves are exploited for lactation, production must suffer. One mechanism for dealing with cold when the animal is below thermoneutral zone is shivering in skeletal muscles, and that can increase metabolic rate. During prolonged cold there can also be an adaptation whereby resting metabolic rate increases by 20-40%, appetite is stimulated and there is an altered perception of cold. Newborn animals also have a capacity for non-shivering thermogenesis from catabolism in mitochondria-rich brown adipose tissue – this capacity is lost after a few days or weeks when that tissue is replaced by white fat (Stevens 1988). Scibilia et al. (1987) found that liveweight gains were significantly lower for dairy calves housed at -4°C than at 10°C. Calves housed at -4°C required 32% more energy for maintenance than calves housed at a temperature within their thermoneutral zone.

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Cows graze less on very cold days than on warm days (>5°C) but may compensate later by eating more rapidly, unless pasture quality or quantity is limiting (Arnold & Dudzinski 1978). Provision of shelter on the treeless veldt in South Africa increased cattle productivity (Arnold & Dudzinski 1978). However, McCarrick & Drennan (1972) in Ireland found no effect of shelter on liveweight gains of Friesian steers in pens in which the steers were fed similar amounts of hay and concentrates to those in unsheltered sawdust pads. The conditions appeared to be fairly severe and so the lack of effect is surprising. It is not clear how much difference there was in the wind exposure among treatments. The unsheltered pad might have been sheltered by nearby buildings. Alternatively, the animals could have adapted to the cold prior to the experiment (Ames & Ray 1983); the exposed steers were observed to develop longer and more dense coats than their housed counterparts. Possibly the relative absence of mud on all treatments also contributed to the lack of difference, since cattle kept in muddy pens during three winters in California grew at 0.95 kg/day compared with 1.35 kg/day for those kept on concrete floors (Morrison et al. 1970). The beneficial effect of shelter on milk production of dairy cattle in cold, wet and windy weather is well known, according to Ames & Ray (1983). However, Muller & Botha (1995) found no significant effect on milk production of shelter from wind and rain on the performance of Friesian cows during winter in a Mediterranean climate in South Africa (maximum and minimum temperatures during the trial were 18.5 and 8.7°C, respectively, and total rainfall was 180.6 mm and a daily rainfall of >5.0 mm was recorded on 12 days). These conditions are probably less severe than might be encountered in southern Australia, particularly where the climate is also more windy. Holmes et al. (1978) investigated the effects of winter weather on the growth rate and heat production of dairy cattle in New Zealand. The provision of shelter, in association with a relatively dry ground surface, increased the rate of liveweight gain of the heifers in the 2 years by 3.6 and 7.2 kg per head over periods of 54 and 44 days, respectively. That represents an average gain of 32%. The average daily temperature (June and July) was 7.4 and 10.2°C in 1976 and 1977, with daily rainfall of 5.6 and 2.9 mm, respectively. Heat production of Friesian bulls and jersey cows was increased by the climatic conditions on only a few occasions when wind speed was high and rain was falling – conditions that reduced the insulative efficiency of the coat. Wet and windy conditions remove virtually all of the insulative properties of the hair coat of Friesian and Jersey cattle. Thus, in windy, wet conditions these cows would be subject to a degree of cold stress even at relatively warm temperatures. In such conditions the lower critical temperatures were from 7°C to 24°C for cattle on a maintenance ration. Yamagishi et al. (1984) concluded that low temperatures did not adversely affect milk yield in dairy cows because there was little difference between those housed at 0°C in a slight breeze (2.5 m/s) and those housed at 18°C and 60% RH, although milk fat and protein content were significantly higher. Yamagishi et al. (1985) also found no significant effect of housing cows at -10°C compared with 18°C. Shijimaya et al. (1985) also found no effect on milk production of keeping cows at peak lactation in a barn with open windows (mean –1.1°C) and cows kept in a barn at mean 4.9° C. It might therefore be concluded that adult dairy cattle are relatively tolerant of cold, although exposure to wind and wet weather are more stressful conditions. Anecdotal evidence includes a report (Barr 1962) that when a shelterbelt near Whenuapai airport, Auckland, was cleared, milk production on a neighbouring farm dropped 11% in spite of a 5.25% increase in the average for herds in the area. Whether this was an effect on pasture production or a direct effect on the cows is not known.

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Selected shade and shelter abstracts from literature 1972-2002 Heat stress in dairy cattle [Anon. (1992) Shade or better management. Australian Farm Journal October issue, pp.60-63] – The most effective shade is from trees, cooling as moisture evaporates from leaves and screening out the radiant heat. However, for feedlots in Queensland, an effective and cheap alternative is shade cloth. Shade cloth (80% shade) is strung 3.5-4.2 m above ground in areas with clear afternoons or 2.1-2.7 m above ground in areas where cloudy afternoons are the norm. This is placed over feeding and watering areas, with from 2-5.6 m2 per head allocated. Shade width of 12-15 m is considered optimal – greater width may impede air movement. In paddocks with shade trees, British breed cattle in the wet tropics zone of northern Australia spent 9-11 hours in shade in summer, 7 in autumn and nil in June. Rumination continues in cattle in shade, an activity that can occupy 5-9 hours daily, whereas this activity is interrupted in unshaded animals. At Rockhampton, Qld, Shorthorns needed shade more than Brahmans, spending 3.8 hours a day in shade compared with 1.6 hours for Brahmans. Access to water is less effective than provision of shade in reducing heat load. Low quality roughage adds to the heat burden in periods of hot weather, since heat increment increases with low digestibility. [Anon (1988) Taking the heat off lactating cows. Agriculture International 40: 6, Dairying update, 3] - Heat stress in lactating cows is a particular problem in S.W. United States (e.g. Arizona, New Mexico) where summer temperatures cause up to 30% decrease in milk production and success rate of only 10-20% for inseminations. Practical steps to alleviate heat stress include diet modifications - increasing concentrates at expense of forage lessens the generation of heat in the rumen. Buffering agents, such as 1% NaHCO3, must be given to maintain quality of rumen fermentation and prevent decreases in milk fat levels. Evaporative coolers in the pens or misting systems in the mangers are well established methods of cooling cows. [Armstrong DV (1994) Heat stress interaction with shade and cooling. Journal of Dairy Science 77: 7, 2044-2050] - Hot weather causes heat stress in dairy cattle. Although effects are more severe in hot climates, dairy cattle in areas with relatively moderate climates are also exposed to periods of heat stress. The resultant decrease in milk production and reproductive efficiency can be offset by implementation of a programme consisting of cooling through shades, ventilation and spray, and fans. The economic benefit should be determined before installation of equipment to reduce heat stress. [Badica D, Draghici C (1983) Effect of solar radiation on milk yield in cows. Lucrarile celui de al 8ea Seminar ameliorarea, tehnologia si patologia rumegatoarelor, Cluj-Napoca, 11-12 noiembrie 1983. Sectia de ameliorare si tehnologie de crestere si exploatare 75-79 (Institutul Agronomic, Romania)] -: Holstein-Friesian (HF) cows spent 5 days in July outdoors with no shade from 08.00 to 16.00 h, while other HF cows were kept outdoors in the shade, and then the treatments were reversed for 5 days. Milk yield during exposure to the sun was reduced by approx. 9% . [Bennett IL, Holmes CR (1987) J. Agric. Sci. Camb. 108: 683-] - The main function of shade is to decrease the heat load by reducing incident solar radiation. Studies with grazing beef cattle have shown that the cows body temperature and use of shade during lactation were correlated with calf birth weight and growth rate to weaning [Bucklin RA, Turner LW, Beede DK, Bray DR, Hemken RW (1991) Methods to relieve heat stress for dairy cows in hot, humid climates. Applied Engineering in Agriculture 7: 2, 241-247] - Hot, humid weather causes heat stress in dairy cows leading to declines in feed intake, milk production and fertility. These declines can be reduced or eliminated by using a heat stress relief program consisting of a combination of shades, feed and water offered under shade, ventilation, and sprinkler and fan cooling. Results from experimental studies in Florida and Kentucky, USA, indicate that sprinkling and fan cooling systems in combination with shades can improve cow comfort and increase milk production of cows in hot, humid climates. [Bempong IA, Gupta LR (1986) Effect of shelter and sprinkling on the production of lactating crossbred cows during summer. Indian Journal of Animal Management 2: 1, 16-19] - For 84 days in May-Aug., 15 lactating Holstein-Friesian X Haryana cows were allotted to 3 equal-sized groups kept in the shade, or in an open paddock with a shelter or as in the 2nd group plus water sprinkling. Treatment had no significant effect on milk yield or composition. Simple and partial correlations of

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milk yield with ambient temp. and relative humidity are tabulated within treatments. Correlations with temp. were positive, and those with relative humidity were negative [Berman A (1991) Reproductive responses under high temperature conditions. Animal husbandry in warm climates. , 23-30, EAAP Publication No. 55. Wageningen, Netherlands; Pudoc] - A review of work mainly on dairy cattle, but also including some on beef cattle and sheep. In warm climates, CR in cattle is depressed during the hotter months to 10-20%, even when food quantity and quality are not limiting. This is associated with lower levels of progesterone, abnormal patterns of progesterone secretion, shorter corpus luteum lifespan, higher oestrogen levels in the preovulatory phase, high incidence of ovulation without behavioural oestrus, smaller mammary glands, reduced calf birth weight and decreased milk yield. [Buffington DE, Collier RJ (1983) Design parameters for shade management systems for dairy cows in hot, humid climates. Dairy Housing II. Proc. Second National Dairy Housing Conference, March 14-16, Madison, Wisconsin, USA. ASAE SP 4-83, 100-107] – Dairy cows with free access to a 30ft by 80ft gable roofed shade structure in Florida were compared with an unshaded control group. A 10% increase in milk production in the summer, improved conception rate and higher milk production in subsequent lactations was found in those cows with access to shade during their entire lactation and gestation periods. [Buffington DE, Collier RJ, Canton GH (1982) Shade management systems to reduce heat stress for dairy cows. Transactions of American Society of Agricultural Engineers No. 82-4061, 16 pp.] - The benefits of providing shade are reported based on > 7 yr of research. Parameters for design and management of shade structures are presented [Canton GH, Buffington DE, Collier RJ (1982) Inspired-air cooling for dairy cows. Transactions of the American Society of Agricultural Engineers 25: 3, 730-734] - The cow's head and neck was cooled, thus cooling the inspired air. The responses were increased feed intake and milk production, with accompanying decreases in rectal temp. and respiration rate. The research was located where the av. daily summer temp. ranges from 24.4-27.8 ºC with an av. max. of 32.2 ºC, with humidity 50-65% during the afternoon and 85-95% at night.. In hot weather conditions with no shade, effective reduction of rectal temp. and respiration rate was achieved with inspired-air treatments of 10 and 15.5 ºC. Some additional benefit can also be achieved by a combination of both shade and inspired-air cooling treatment of 10 ºC. However, reduction of the mean radiant temp. by a well-designed shade structure is more beneficial economically in reducing heat stress than inspired air cooling. [Carvalho N de Madruga, Olivo CJ, Buriol G Adeli, Madruga de Carvalho N, Jorge Olivo,C, Adeli Buriol G (1993) Effects of shade availability on the milk yield of Holstein cows during the summer. Ciencia Rural 23: 1, 73-79] - This work was undertaken in Brazil with Holstein-Friesian cows, when given or not given access to shade during the hottest part of the day in summer. After 55 days, a clear tendency emerged for cows in the no-shade group to show lower yields and, among these, the cows which had previously had higher yields were the most affected. Shade should be provided for lactating dairy cows, and especially for high-yielding cows, during the hottest part of the day in summer. [Coleman DA, Moss BR, McCaskey TA (1996) Supplemental shade for dairy calves reared in commercial calf hutches in a Southern climate. Journal of Dairy Science 79: 11, 2038-2043] - A study was conducted during 2 consecutive years to determine the effects of providing supplemental shade to dairy calves reared in commercial hutches made of translucent plastic in a southern environment (Alabama, USA). Shade reduced temperatures both inside the hutches and in the outer exercise areas during both years. However, shade increased humidity in the exercise area during year 1. Shaded calves had lower rectal temperatures than control calves during year 1, but differences were not significant during year 2. Shade did not alter plasma cortisol concentrations. Shaded calves consumed less concentrate feed but had average daily weight gains that were similar to those of control calves, resulting in a tendency for greater feed efficiency for shaded calves. Providing supplemental shade to calves reared in plastic hutches in a warm southern environment had little effect on overall growth and health.

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[Collier RJ, Sharma AK, Thatcher WW, Wilcox CJ, Buffington DE (1979) Effects of shade on maternal parameters, calf birth weight and subsequent milk yield. Journal of Dairy Science 62: Suppl. 1, 118] - In 16 cows assigned to shade and 15 assigned to no-shade treatments during the last trimester of pregnancy in June 1978, milk yield, corrected for age, body wt., estimated real producing ability and days in milk (120 ±5 and 126± 7 days resp.), was 2805± 136 and 2612± 136 kg resp. (P < 0.05). No-shade treatment reduced birth wt. of calves. [Collier RJ, Eley RM, Sharma AK, Pereira RM, Buffington DE (1981) Shade management in subtropical environment for milk yield and composition in Holstein and Jersey cows. Journal of Dairy Science 64: 5, 844-849] - For 102 days beginning in June, 31 Holstein-Friesian and 17 Jersey cows were kept in shaded or unshaded areas; observations were made on 20 days after 42 days adaptation. Black globe temp. (BGT) averaged 30.1°C in shade and 38.8°C in no-shade. For shaded and unshaded cows resp., av. rectal temp. (RT) was 38.7 and 39.6°C, respiration rate (RR) was 78.5 and 114.8/min and rumen contraction rate (RC) was 2.3 and 1.6/min, all differences were significant (P <0.01). Jerseys had a higher RT and RC than Holstein-Friesians (P <0.05). RR and RT increases sharply in both breeds only when BGT exceeded 35°C; RC was inversely related to BGT and RT (P <0.001). Yield at 1st and 2nd milking was not affected by BGT on the day of milking but decreased as BGT during the previous 24 or 48 h increased. Shading did not affect milk protein or fat contents, acidity, freezing point depression or somatic cell count but the total solids content of milk was higher from the 2nd milking of the day at 2100 h than from the 1st milking at 1300 h [Collier RJ, Doelger SG, Head HH, Thatcher WW, Wilcox CJ (1982) Effects of heat stress during pregnancy on maternal hormone concentrations, calf birth weight and postpartum milk yield of Holstein cows. Journal of Animal Science 54: 2, 309-319] -cows and heifers were assigned to shade or no shade during the last trimester of pregnancy. At parturition, all cows were removed from the treatments, and were uniformly managed in the milking herd. Black globe temp., rectal temp. and respiration rates were higher in cows given no shade, and calf birth weight was also lower in this group. Milk yield was correlated linearly with calf birth weight, and cows given no shade exhibited a reduced lactation performance after calving. Plasma progestin concentrations were higher in heat-stressed cows than in cows given shade (6.0 vs. 5.1 ng/ml). Oestrone sulphate concentrations were reduced in the plasma of cows given no shade (2505 vs. 4433 pg/ml). Plasma thyroxine concentrations were lower in cows given no shade (51.2 vs. 66.4 ng/ml), while plasma triiodothyronine concentrations were elevated (1.8 vs. 1.5 ng/ml), indicating altered thyroid hormone metabolism in heat-stressed cows. Heat stress altered endocrine dynamics during pregnancy and reduced calf birth weight, and may have indirectly altered subsequent milk yield. [Cowan RT, Moss RJ, Kerr DV (1993) Northern dairy feedbase 2001. 2. Summer feeding systems. Tropical Grasslands 27: 3, 150-161 (paper presented at 'Northern dairy feedbase 2001' held at Cedar Lake, Nerang, Queensland, March 29-31 1993)] - Relatively low milk production per cow is one of the key limitations to productivity during summer and autumn. The low production is associated with a high fibre content in pasture and low DM digestibility. Various grazing management strategies have failed to increase the daily milk yield of Holstein-Friesian cows beyond 13 kg/cow. Heat stress is a key limitation to productivity during summer and autumn, with Holstein-Friesian cows not grazing between morning and afternoon milking once daily maximum temperature exceeds 30°C. More emphasis will be given to legumes, particularly Medicago sativa, Trifolium spp. and crop legumes, for grazing. Conserved fodders such as Zea mays silage and M. sativa hay will be a substantial component of the feed supply, for feeding during the day at shaded feed pads close to the dairy. Cows will graze during the night. Substantially higher levels of concentrate will be used as these have a similar milk output:cost ratio to forages, reduce heat load in cows and are well suited to dairy and feed pad feeding methods. [de Aguiar IS, Targa LA (1999) Thermoregulatory responses, heat storage and milk production of Holstein cows exposed to global solar radiation and with access to natural shade. Energia na Agricultura 14: 4, 9-21] - This work was carried out during the autumn of 1997, with 10 black-spotted Holstein cows averaging 638.2 kg, 87.2 days in lactation and 20.6 kg milk/day. After an adaptation period of 20 days when all animals were kept in the same sod area with access to tree shade, cows were paired according to stage of lactation and milk production, and divided into 2 equal groups of 5: one was maintained under direct solar radiation (group 1, G1) and the other had access to natural shade provided by tree (group 2, G2), for 30 days. Water (ad lib.) and feeding (concentrate ration, 3%

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live weight, twice daily) were provided in the sod area. From 0800 to 1600 h, air temperature and temperature-humidity index (THI) were 0.8°C and 3.6 units above the upper critical values for lactating Holstein cow (21°C and 64). Temperature-humidity index, black-globe temperature, black-globe humidity index (BGHI) and wind speed for shaded and non-shaded areas were 67.6, 27.8°C, 73.2, 1.5 m/s and 67.6, 22.4°C, 67.8 and 1.6 m/s respectively. From 1600 to 0800 h all climatic variables remained within the thermo-neutral zone. In both groups, respiratory frequency, black spot temperature, white spot temperature and rectal temperature were greater in the afternoon than in the morning and average values (morning plus afternoon) were lower for shaded than for non-shaded cows (38.13 vs. 40.06 breaths/min; 31.14 vs. 31.33°C; 30.10 vs. 30.68°C, 38.64 vs. 38.69°C respectively). The thermal circulation index was higher for G1 than for G2 (1.44 vs. 1.35). There was a trend for shaded cows to store less heat (9.6%) than non-shaded cows (237.61 vs. 262.85 kJ/m2) from morning to afternoon (8 h duration) and to produce 12.9% more milk (21.9 vs. 19.4 kg/day) respectively. There was no improvement on thermal comfort or milk production by providing Holstein cows with tree shade, when compared to global solar radiation, under the prevailing conditions of a mild heat stress. [Draghici C, Badica D, Balint A, Hilliger HG (ed.) (1985) The influence of solar heat radiation on milk production in cow. Proc. 5th International congress on animal hygiene, Hannover, 10-13 September 1985. Volumes I and II, 435-440 (Deutsche Veterinarmedizinische Gesellschaft, Frankfurter Strasse 87; D-6300 Giessen; German Federal Republic)] - In an area of Romania with an annual solar radiation of 110-115 kcal/cm2, Holstein-Friesian cows were exposed to the sun in July (17.1 kcal/cm2) and Sept. (11.38 kcal/cm2) and milk yields were compared with those of cows kept in the shade. Exposure to the sun resulted in increases of 96% in respiration rate and 34.7% in pulse rate and an increase of 1.57-1.63°C in rectal temp. Daily milk production per cow decreased by 1.63 L after exposure to the sun, and increased by 1.6 L when cows were kept in the shade after being in the sun for 5 days. In trials with Romanian Piebald cows, a local breed, there were reductions in milk yield of 0.97 and 0.38 L per cow after exposure to the sun in July and Sept., resp. On rainy days, when all cows were kept indoors, milk yields continued to be lower in cows previously exposed to the sun, indicating that the solar radiation effect persists for several days. [Dragovich D (1978) Influence of high temperatures on milk production of Friesian dairy cows grazed on farms in a pasture-based feed system. International Journal of Biometeorology 22: 4, 277-284] - Data on daily milk yields at 3 dairy farms having some irrigated feed and located in a semi-arid climate in New South Wales, Australia, were collected for a 2-yr period. The possible short-term effects of high temperature on production were examined by aggregating data for the 3 farms and comparing production on hot days (max. temp. >27ºC) with that on other days. No significant differences were observed between production on hot days and other days, nor between production on days having varying heat intensities above the 27ºC threshold. Neither prolonged periods of high temp. nor the rapid onset of hot weather resulted in consistent declines in farm production. Even though the farm data used were affected by uncontrolled variables, the temperature conditions examined did not constitute the dominant factor affecting short-term production fluctuations. Feed of adequate quality and quantity, and acclimatisation of cows to temperatures that were often not greatly above the 27 degree threshold, probably contributed to the lack of a significant decline in production in association with high temperatures. [Du Preez JH, Giesecke WH, Hattingh PJ (1990) Heat stress in dairy cattle and other livestock under Southern African conditions. I. Temperature-humidity index mean values during the four main seasons. Onderstepoort Journal of Veterinary Research 57: 1, 77-87] - The Livestock Weather Safety Index (LWSI) indicates that in large areas of South Africa and Namibia, for prolonged periods of the year, warm conditions are causing heat stress in food-producing animals, especially dairy cattle, thereby hampering their performance. South Africa and Namibia have been mapped according to a modified LWSI, which includes the critical "temperature-humidity index" value for milk production. Cattle should be protected against heat stress by zootechnological arrangements (e.g. shade, moving of air, wetting). [du Preez JH, Hattingh PJ, Giesecke WH, Eisenberg BE, Du Preez JH (1990) Heat stress in dairy cattle and other livestock under Southern African conditions. III. Monthly temperature-humidity index mean values and their significance in the performance of dairy cattle. Onderstepoort Journal of Veterinary Research 57: 4, 243-248] - Temperature-humidity index (THI) values applicable to South

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Africa and Namibia were established for each month of the year by means of computerized modelling and mapping techniques. The data indicate that each year heat stress risk areas (HSRA's) expand from August to January and retract from February to July. The THI values classified according to the Livestock Weather Safety Index (LWSI) for lactating dairy cattle (LDC) suggest that, especially during November to March, there is the risk of moderate to advanced heat stress in most South African dairy cows. [Ealy AD, Drost M, Hansen PJ (1993) Developmental changes in embryonic resistance to adverse effects of maternal heat stress in cows. Journal of Dairy Science 76: 10, 2899-2905] - Superovulated, lactating Holstein cows were bred and assigned to be heat-stressed on days 1, 3, 5 or 7 of pregnancy (day 0 = day of oestrus) or not heat-stressed (controls). Compared with embryos of controls, embryos of cows receiving heat stress on day 1 had decreased viability and development. Heat stress on other days had no detrimental effect on embryonic viability or stage of development. It is concluded that embryos become more resistant to adverse effects of maternal heat stress as pregnancy progresses; substantial resistance develops by day 3. [Eley RM, Collier RJ, Bruss ML, Horn HH van, Wilcox CJ (1978) Interrelationships between heat stress parameters and milk composition and yield in dairy cattle. Journal of Dairy Science 61: Suppl. 1, 147] - Milk composition and cell count did not differ significantly between 35 cows kept without or with shade for 102 days, with black globe temp. of 38.8 or 30.0ºC. F.p. depression was greater in p.m. milk and this difference was accentuated without shade. Heat stress parameters were greater without shade, and were paralleled by decreasing milk yield, more significantly in Holstein-Friesians than in Jerseys. [Francos G, Mayer E (1981) The influence of thermal stress on the fertility of dairy cattle. Refuah Veterinarith 38: 1-2, 6-11] - The effect of thermal stress on the fertility of cows was examined in dairy herds in the northern part of Israel in 1979. In 28 herds the fertility depression during the hot summer months was slight. The overall conception rates in these herds, year round, during April-May and during July-September were 45.3, 50.6 and 40.6%, respectively. In another 21 herds in which the fertility depression during the summer months was greater, the corresponding rates were 37.5, 43.3 and 22.4%. It is suggested that a good fertility status of a herd is associated with a better ability to withstand thermal stress, probably due to favourable conditions of husbandry. [Garrett WW, Bond TE, Kelly CF (1960) Effect of air velocity on gains and physiological adjustments of Hereford steers in a high temperature environment. J. Anim. Sci. 19: 60-66] – shaded cattle required 143 kg less feed per 100 kg of gain than unshaded animals. [Gaughan JB, Goodwin PJ, Schoorl TA, Young BA, Imbeah M, Mader TL, Hall A (1998) Shade preferences of lactating Holstein-Friesian cows. Australian Journal of Experimental Agriculture 38: 1, 17-21] - Shade preferences of Holstein cows were investigated under natural climatic conditions in South-East Queensland, Australia, during 88 days in the summer. Cows were placed in a dirt-floored yard (zero grazing) provided with different shade types: (i) a 3 m high galvanised iron roof: (ii) Sechium edule (choko) vines on a 3 m high trellis; (iii) 70% shade cloth on a 3 m high frame; and (iv) natural shade provided by trees. The floor area under the shade structures was concrete. An unshaded area (the remainder of the yard) was also provided. Each cow was scored for coat colour based on the proportion of black and white. Number of cows using a particular shade type and their respiration rates were recorded daily at 13.00 h. Ambient temperature, relative humidity, solar radiation and wind speed were also measured. Cows selected (i) most frequently when temperatures increased to >30°C, with no significant differences between the other shade types. At temperatures <30°C, cows did not seek shade. As ambient temperature, solar radiation and relative humidity increased, respiration rate increased. Cows with a high percentage of black coat preferred shade, while those with a high percentage of white coat did not seek shade. [Goodwin PJ, Gaughan JB, Schoorl TA, Young BA, Hall A, Bottcher RW (ed.), Hoff SJ (1997) Shade type selection by Holstein-Friesian dairy cows. Livestock environment 5, Volume 2. Proc. Fifth International Symposium, Bloomington, Minnesota, USA, 29-31 May, 1997. p. 915-922 (American Society of Agricultural Engineers; St Joseph; USA)] - The selection of different shade types by Holstein-Friesian cows was investigated under different temperature conditions. The trial was conducted in south-east Queensland, Australia, over 88 days in summer 1992/1993. Forty-two cows

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were placed in a gravel floor yard (zero grazing) provided with different types of shade and their behaviour, in terms of shade type preferences, was monitored. Shade types provided were galvanized iron roof 3 m high, Sechium edule (choko) vines on a 3 m high trellis, 80% shade cloth on a 3 m high frame, and natural shade trees. An unshaded area was also provided. Each cow was scored for coat colour based on its proportion of black and white. The number of cows using a particular shade type and their respiration rates (RR) were recorded daily at 1300 h. Ambient temperature, relative humidity, solar radiation and wind speed were also measured. Cows selected the galvanised iron roof most frequently when temperatures rose above 30°C, with no significant differences between other shade types. At temperatures below 30°C, animals did not seek shade. RR rose as ambient temperature rose, but shade type did not affect RR. Cows with a high percentage of black coat preferred shade, while those with a high percentage of white coat did not seek shade [Gregory NG (1995) The role of shelterbelts in protecting livestock: a review. NZ Journal of Agricultural Research 38: 423-450] - Providing shelter from the sun in hot conditions has been shown to improve milk yield, milk fat yield, freedom from mastitis, conception rates in dairy cattle and growth rates in fattening cattle. The welfare benefits from shelterbelts and shade are implicit in their greater use during hot-sunny conditions and they relate to the thermal comfort of the animals. Some of the original studies on shade showed no effects on milk production. However, milk yield is more related to Temperature Humidity Index than to temperature alone. High-performing herds are more susceptible to a rise in THI. [Grossman R, Steinhauff D, Weniger JH (1984) Reaction of differently acclimatised lactating cows to heat stress. Zeitschrift fur Tierzuchtung und Zuchtungsbiologie 101: 3, 182-187] - During their 1st lactation and up to the beginning of the experiment in their 2nd lactation, 6 German Black Pied cows were housed at an av. temp. of 28°C and a RH of 50%, while 6 similar cows were kept at <18°C and a RH corresponding to outdoor conditions (controls). During the first 8 wk of their 2nd lactation, all cows were kept in a climate chamber at 34° during the day and 20° at night, and during the next 4 wk at a constant temp. of 27° night and day. Milk yield was depressed in both groups of cows during the first week of the experiment relative to their yield during the last week of the 1st lactation, but the group which had been heat-stressed in the previous lactation reacted less adversely than the control group. The controls yielded 5.7 kg more milk than the heat-stressed group during the 1st wk of the experiment, but thereafter the weekly difference between the 2 groups averaged only 1.4 kg. There were no significant differences in milk yield between the 2 groups in any of the 12 wk of the experiment. During the last 4 wk, the constant heat stress had little deleterious effect on the cows, 8 of which reacted by an increase in their milk yield during this period. The effects of heat stress on water intake, body temp., respiration frequency and time spent standing were also studied. [Hansen PJ (1990) Effects of coat colour on physiological responses to solar radiation in Holsteins. Veterinary Record 127: 13, 333-334] - Lactating Holstein cows were classified as white or black. The first group were exposed to an unshaded environment for 2 weeks followed by 2 weeks in a shaded environment. Cows in group 2 were in shade for period one followed by no shade in period 2. Rectal temperature, surface temperature, breaths/minute and open mouthed panting were all affected by colour X environment interaction: the increase caused by exposure to no shade was less for predominantly white cows than for predominantly black cows. Average daily milk production also tended to be affected by a similar interaction, with a depression in milk production caused by placing cows in the no shade environment of 1.5 kg for predominantly white cows and 3.3 kg for predominantly black cows. [Igono MO, Johnson HD, Steevens BJ, Krause GF, Shanklin MD (1987) Physiological, productive, and economic benefits of shade, spray, and fan system versus shade for Holstein cows during summer heat. Journal of Dairy Science 70: 5, 1069-1079] - During summer 1984, 24 cows were kept in shaded cubicles without (control) or with sprays (20 min on, 10 min off) and fans (air flow 6.6 m/s) which operated when temp. increased beyond 27°C. For both groups dry bulb temp. averaged 22 and 31°C at 04.00 and 16.00 h resp. and RH 78 and 43% resp. Spraying and fanning enables cows to regain normal body temp. by a.m. milking. Diurnal studies showed that although temp./RH conditions were similar for both groups, spraying and fanning decreased rectal temp. by 0.3-1.2°C and kept it below 39°C. Compared with controls, the sprayed-fanned cows averaged 2 kg more milk per day with lower somatic cell counts, and had higher blood somatotropin and prolactin concn. The calculated increase in net income per cow from the sprays and fans was $0.22/day

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[Igono MO (1986) Effect of a humid temperate climate and environmental modifications with shade, spray, and fan, on milk production, thermal balance and hormone function to dairy cows. Dissertation Abstracts International, B Sciences and Engineering 46: 11, 3645] - Provision of shade reduced air temp. under the shade during summer by 28% for 10-12 h per day. Provision of a water spray and a fan under the shade did not alter the environmental temp., but reduced climatic stress as measured by rectal, milk and skin temps., evaporative heat loss, respiration rate and concentrations of galactopoietic hormones. Spraying under shade increased daily milk yield by 1.6 kg. In 1984, spraying under shade plus use of fans reduced milk and rectal temps., and increased daily milk yield by 2 kg compared with cows under shade without spray or fan. In 1983, cows provided with shade had a rectal temp. >39°C for 19.8 h per day vs. 11.8 h for cows offered shade plus spraying; corresponding values in 1984 were 12 vs. 0 h. At 10.00 h on an extremely hot day, rectal temp. in 89 Holstein-Friesians showed significant differences among stages and intensities of lactation; the av. value was 39°. A 1-yr study indicated that the annual trends in milk somatic cell count, milk temp. and milk prolactin concentration were directly related to environmental temp., and that growth hormone concentration in milk was inversely related to environmental temp. [Igono MO, Bjotvedt G, Sanford-Crane HT (1992) Environmental profile and critical temperature effects on milk production of Holstein cows in desert climate. International Journal of Biometeorology 36: 2, 77-87] - The environmental profile of central Arizona, USA, is quantitatively described using meteorological data between 1971 and 1986. Utilizing ambient temp. criteria of h per day less than 21°C, between 21 and 27°C, and more than 27°C, the environmental profile of central Arizona consists of varying levels of thermoneutral and heat stress periods. Milk production data from 2 commercial dairy farms from March 1990 to Feb. 1991 were used to evaluate the seasonal effects identified in the environmental profile. Overall, milk production is lower during heat stress compared with thermoneutral periods. During heat stress, the cool period of h per day with temp. less than 21°C provides a margin of safety to reduce the effects of heat stress on decreased milk production. Using min. mean and max. ambient temp., the upper critical temp. for milk production are 21, 27 and 32°C resp. Using the temp.-humidity index (THI) as the thermal environment indicator, the critical values for min., mean and max. THI are 64, 72 and 76 resp. [Jahn E, Arredondo S, Bonilla W, Pozo A del, del Pozo-A (2002) Effect of temperature and energy supplementation on milk production of grazing dairy cows. Agricultura Tecnica 62: 2, 245-254] - A study was carried out to evaluate the effect of supplementation in the shade in summer months for cows grazing on a perennial pasture of clover-ryegrass (Trifolium repens L. - Lolium multiflorum L.). Four treatments were compared: I. Day and night grazing without supplementation; II. Day and night grazing plus supplementation; III. Day and night grazing plus supplementation in the shade between 11:30 and 17:00 h; and IV. Day and night grazing plus supplementation in the sun between 11:30 and 17:00 h. 32 Holstein cows were used. There were no significant treatment effects on milk production; highest production was observed on treatment III (19.5 litre d-1). Highest ambient temperatures during January and February where 33.5 and 34.5°C, respectively. [Johnson HD, Shanklin MD, Hahn L (1989) Productive adaptability indices of Holstein cattle to environmental heat. Agricultural and Forest and Meteorology Conference 291-297, Boston, USA; American Meteorological Society] - Holstein cows, producing >20 kg of milk/day during a 3-yr study at 3 stages of lactation, were exposed to short-term heat (3 days at 32°C). Heat exposure reduced milk yields and feed intake, and increased rectal temp. and water intake at all stages. Four days after being exposed to heat, milk yields and feed intake had not recovered, whereas rectal temp. and water intake recovered significantly. Nine or 10 days were needed to recover thermoneutral milk levels for early- or mid- and late-stage resp. Early-stage cows had a greater conversion ratio of feed:milk (milk/feed, Mcal) than mid or late stages during thermoneutral conditions and heat increased this ratio. A review of the frequency distributions for av. individual cow responses to heat (all l3 stages) for rectal temp., milk yield and feed intake suggested the development of a heat tolerance (positive productive adaptability) and heat sensitivity (negative productive adaptability) index. These data and the index re-emphasized the dependency of lactation during heat stress on maintenance of thermoneutral core body temp., and the ability of the animal to maintain homeothermy and continue adequate feed intake. [Kelov D, Kolesov N (1974) Summer housing of cows in hot climates. Molochnoe I Myasnoe Skotovodstvo No. 6, 16-17] - A study was made of physiological indices of cows kept under different

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conditions in Turkoman USSR during the summer of 1972, including body temp., pulse, respiration and skin temp. Max. ambient temp. of 39.8 ºC was recorded in June. Keeping the cows in the open without shade resulted in increased body temp. and higher pulse and respiration rates and decreased body wt. and fat % in the milk. It is concluded that for maintaining the milk yield during the summer in Turkoman SSR, it is necessary to use awnings for shelter and to feed green fodder under them. [Kelov DN (1975) Keeping cattle in a hot climate. Veterinariya Moscow, USSR, No. 7, 26-29] - Dairy cattle introduced into Turkmenia (USSR) tend to show a decrease in milk yield due to the hot climate. In an experiment during May-Sept., 48 cows which from 10 a.m. to 5 p.m. each day were shaded by a special canopy alongside the cowshed, gave significantly higher milk yields and milk fat % than a control group left in an unshaded yard. [King KR, Stockdale CR (1981) Milk yield of dairy cows given restricted access to water in a Mediterranean-type climate. Australian Journal of Experimental Agriculture and Animal Husbandry 21: 109, 167-171] - During summer in the Goulburn Valley, Victoria, Jersey X Friesian cows were given restricted access to drinking water. There were 3 treatments applied to 2 herds; free access; 20 min access before each milking; 20 min access before the night milking only. One herd was penned and had free access to shade while the other grazed with no access to shade. Both herds were on irrigated perennial pasture containing 24.5% DM. Maximum air temperature averaged 33.7°C. Over the whole experiment, restricting the access of dairy cows to drinking water did not significantly reduce mean milk yield (mean 12.6 kg/cow daily) or mean liveweight of cows (mean 411 kg) in either herd. During the first 4 days of treatment, mean milk yield and mean liveweight were significantly lower for cows on a once-a-day access than for those on free or twice-daily access. In the pen, daily intake of drinking water averaged 67, 45 and 49 litres for treatments 1, 2 and 3, respectively; DM intake was unaffected by treatment (mean 15.6 kg daily). Because of the modifying influence of shade on the environment of the penned cows, there was no significant effects of climate on their water intake. It was concluded that farmers need not supply drinking water to dairy cows in all paddocks. [Korsun BA (1993) Feeding cows under shaded awnings during summer. Molochno M'yasne Skotarstvo 82: 52-54.] - The effect of providing a shaded area for feeding cows in loose housing conditions on milk yield, feed intake and cow behaviour during hot summer conditions was studied using Russian Black Pied cows on the "Parkhomivs'kii" state farm (Krasnokuts'kii Raion, Ukraine) and the "Kutuzivka" experimental farm (Kharkivska Oblast', Ukraine). Feed consumption decreased for all cows when air temperatures were >24°C, water consumption increased and time spent ruminating decreased. Feed consumption of animals in shady conditions was on average 9% higher than those without shade, and the level of aggressive behaviour (determined by the number of collisions between cows) was 32-38% lower. Milk yields of cows kept in shady conditions were on average 5.2% higher than those of cows kept without shade. [Kume S (1992) Mineral requirement of dairy cows under high temperature conditions. Proc. 25th International Symposium of Tropical Agricultural Research Tsukuba, Japan, September 24-25, 1991. Tropical Agriculture Research Series, No. 25, 199-207] - Heat stress in summer alters mineral needs in ruminants. Mineral requirements for maintenance in dairy cows increased at temperature above 27°C. Calcium, phosphorus, magnesium and sodium contents in milk decreased, while the contents of other elements were not affected by heat stress. Ca and P balances in lactating cows were negative when milk production was high under optimum temperature conditions. Since the intake and apparent absorption of major mineral and trace elements in lactating cows were depressed by heat stress, it is suggested that the mineral requirements in lactating cows increase under high temperature conditions. [Kurihara M (1992) Energy requirements of dairy cows under high temperature conditions. Proc. 25th International Symposium of Tropical Agricultural Research Tsukuba, Japan, September 24-25, 1991. Tropical Agriculture Research Series, No. 25, 208-216] - Heat stress causes the decrease in voluntary feed intake and milk production in dairy cows. Heat stress also affects energy requirements due to the higher metabolic activities and increase in the investment for heat dissipation to cope with the stress. The net energy requirements of dry cows for maintenance were almost constant at 18°, 27° and 32°C and tended to increase by about 5% at 36°C. However the metabolizable energy (ME) requirements of dry cows given roughages for maintenance started to increase at lower environmental temperatures than 32°C. The increase in the ME requirements for maintenance was affected by the type of roughage given due to the difference in heat increment among roughages. The energy requirements of

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lactating cows increased at high environmental temperatures, due to the increase in the ME requirements for maintenance. [Lacetera N, Bernabucci U (2000) The production of dairy cows in a hot climate. Informatore Agrario 56: 31, 39-41] - Changes in the metabolism, reproductive efficiency and milk yield of cows bred at THI (temperature-humidity index) above 72 were analysed. It is reported that, in such conditions, the cows' body condition score and glycaemia dropped while blood levels of unsaturated fatty acids and ketone bodies increased. Mineral imbalance also occurred due to a reduction in feed intake and an increase in water loss. Hot climate conditions were also responsible for a decrease in reproductive efficiency due to reduced hormone secretion, duration of oestrus and embryonic survival and an increase in the incidence of ovarian cysts, placental malformation and placental retention. Milk yield was also negatively affected with a reduction in the quantity (-25-30%) and quality of the milk produced (-0.2 to -0.5% fat,-0.1 to -0.3% proteins, -0.1 to -0.3% lactose). Heat stress also affected the composition of the colostrum which had lower pH and reduced content of immunoglobulins (Ig), casein, lactalbumin, fat and lactose. The content of Ig in the blood of calves born during the summer months was also reduced with a higher mortality rate for calves born during the summer or winter. [Lean IJ, Rich JC (1985) Aspects of dry lot feeding dairy cows in Australia. The challenge: efficient dairy production. Proc. conference organized by the Australian and New Zealand Societies of Animal Production. March 25-28 1985, Albury-Wodonga, Australia. 156-170 (Australian Society of Animal Production)] - The paper considers processing methods for feedstuffs, energy and protein input/output relationships, the use of protected proteins and fats, forage:concentrate ratios and fibre, and management of shade and water. [Macfarlane JS, Stevens BA (1972) The effect of natural shade and spraying with water on the productivity of dairy cows in the tropics. Tropical Animal Health and Production 4: 4, 249-253] - The effect of natural shade provided by grazing under coconut palms, and of spraying with water 3 times/day, on the milk yield of Boran (Bos indicus) and Friesian X Boran (50% Bos taurus) dairy cattle was examined. The shade treatment was held constant for any one cow lactation, but the spraying treatment was a single-reversal with an extra period to assess carry-over effects. Shade had a very highly significant effect on the Friesian crosses, increasing milk yield by 18.4%, but a non-significant depressing effect on milk yield of the Borans. The effect of spraying was non-significant in both breeds. [Mallonee PG, Beede DK, Collier RJ, Wilcox CJ (1985) Production and physiological responses of dairy cows to varying dietary potassium during heat stress. Journal of Dairy Science 68: 6, 1479-1487] - Jersey cows in early lactation and Holstein-Friesian (HF) cows in mid-lactation were in 2 groups kept shaded or unshaded throughout the trial and given diets containing added KCl to give total potassium at 0.66, 1.08 or 1.64% in a Latin-square design with 30-day periods. Daytime (0800-1600 h) feed intake was 56% lower and night-time (1600-0800 h) intake was 19.5% higher for unshaded than for shaded cows. Milk yield was decreased by 20% at p.m. milking and 18.5% overall in unshaded cows, but after equalizing feed intakes there was no significant difference between the shaded and unshaded groups; milk composition was not affected by shading. The results suggest that heat-stressed cows have increased requirements for K and benefit from a dietary content of 1.08%. [Marschang F (1972) Effects of heat stress on milk production in cows. Deutsche Tierarztliche Wochenschrift 80: 8, 187-189] - Between Mar. and Oct. 1971, the av. daily milk yield/cow, corrected to 3.5% fat, of a herd of imported Danish Black Pied cows was studied in relation to outside air temp. In addition, 80 cows (28.5% of the herd), all in their 2nd lactation, had their milk yields studied in relation to months of calving. High temps. were found to cause a drop in milk production, the decrease being directly correlated with intensity and duration of the heat stress. Byre temps. were about 1-3°C above outside temps. It is believed that when the mean daily byre temp. rises above 18°C, milk production begins to fall. The av. daily milk yield rose from 9.2 kg in Aug. (mean daily temp. of 28°C) to 12.2 kg in Sep. (mean temp. of 13°C). For milk production, it was disadvantageous for cows to calve during the summer or early autumn as heat stress in late pregnancy caused them to be poorly prepared for their next lactation. [Marschang F, Schlauch I (1973) Observations on the effect of a hot summer on the reproductive performance of dairy cows. Zentralblatt fur Veterinarmedizin A 20: 8, 654-660] - Observations were

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made from May to Sep. during 1970 and 1971 on a herd of 280 Danish Black Pied cows. A relationship was found between environmental temp. and reproduction. During the 2 hottest months, the poorest CR rates to AI were obtained. It was also found that heat stress inhibited foetal development at all stages of pregnancy but particularly the last stage. [Marschang F (1973) Effect of heat stress on milk production in cows. Deutsche Tierarztliche Wochenschrift 80: 8, 187-189] - The effects of climatic conditions on milk yield and composition were measured in a herd of 80 imported Danish Black Pied cows near Timiswara, Rumania during March-Oct. 1971. High ambient temp. caused a decrease in milk yield and milk fat content which was related directly to the temp. and the time of exposure. A decrease in the mean day temp. from +28ºC in Aug. to +13ºC in Sept. was accompanied by an increase in the daily milk yield per cow from 9.2 to 12.2 kg. The critical temp. in the cowshed, above which a decline in milk yield could be expected, appeared to be approx. 18ºC. It is pointed out that forced ventilation is required for cowsheds during summer time. [Mayer DG, Davison TM, McGowan MR, Young BA, Matschoss AL, Hall AB, Goodwin PJ, Jonsson NN, Gaughan JB (1999) Extent and economic effect of heat loads on dairy cattle production in Australia. Australian Veterinary-Journal 77: 12, 804-808] - To investigate the effect of heat load, caused by the combination of excessive temperature and humidity, in Holstein-Friesian cows in Australia, long-term meteorological data for Australia were analysed to determine the distribution of hot conditions over space and time. 15 milk production regions were identified for higher-resolution data analysis. Both the raw meteorological data and their integration into a temperature-humidity thermal index were compiled onto a computer program. This mapping software displays the distribution of climatic patterns, both Australia-wide and within the selected dairying regions. Graphical displays of the variation in historical records for 200 locations in the 15 dairying regions are also available. As a separate study, production data from research stations, on-farm trials and dairy factory records were statistically analysed and correlated with the climatic indices, to estimate production losses due to hot conditions. Both milk yields and milk constituents declined with increases in the temperature-humidity index. The onset and rate of this decline are dependent on a number of factors, including location, level of production, adaptation, and management regime. These results have been integrated into a farm-level economic analysis for managers of dairy properties. By considering the historical patterns of hot conditions over time and space, along with expected production losses, managers of dairy farms can now conduct an economic evaluation of investment strategies to alleviate heat loads. These strategies include the provision of sprinklers, shade structures, or combinations of these. [Moran JB (1989) The influence of season and management system on intake and productivity of confined dairy cows in a Mediterranean climate. Animal Production 49: 3, 339-344] - Intakes of food and water, and milk yields were measured in 154 Friesian cows over 2.5 yr while intensively managed in yards giving access to shelter (free stalls) or fully exposed to solar radiation (open lots). The highest milk yields and energetic efficiencies were recorded during spring. Energy intakes were highest but energetic efficiencies were lowest during winter. Cows consumed the least food during summer and autumn, and drank the most water during summer. Water intake was higher in the open lots than in the free stalls. There was evidence of heat stress in summer and cold stress in winter, but there appeared to be little benefit to milk yields through the provision of shelter. [Moallem U, Gur P, Shpigel N, Maltz E, Livshin N, Yacoby S, Antman A, Aizinbud E (2002) Graphic monitoring of the course of some clinical conditions in dairy cows using a computerized dairy management system. Israel Journal of Veterinary Medicine 57: 2, 43-49] - The most widespread stress observed in cows was heat stress during summer. Walking activity, milk fat, and milk yield decreased. [McIlvain EH, Shoop MC (1971) Shade for improving cattle gains and rangeland use. J. Range Management 24:181-184] – For Herefords grazing rangeland in Oklahoma, high summer humidity depressed gains much more than did high summer temperatures. The combined effects of humidity above 45% and temperature above 85°F were especially harmful.. Each such day affected gains by 1 lb. Shade was nearly as effective as location of water and supplementary feed in drawing cattle to under-utilsed range pastures. South-facing open sheds did not increase steer gains in winter, nor did the steers use them.

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[McGovern RE, Bruce JM (2000) A model of the thermal balance for cattle in hot conditions. Journal of Agricultural Engineering Research 77: 1, 81-92] - To assess the effect of a particular set of environmental conditions on a cow, the thermal balance is modelled and coded into a user-friendly software package. Air temperature, humidity, wind speed and radiation, together with metabolic heat production, are used to evaluate the thermal balance. Three biological cooling mechanisms are included: reduction of thermal resistance of body tissue, sweating to increase the latent heat loss from the skin and panting to increase heat loss from the respiratory system. The body temperature rises if the cooling mechanisms cannot dissipate sufficient heat. The model is used to examine the effects of conditions likely to be experienced by cattle in Southern UK. The results show that high-yielding cows would be able to maintain thermal balance in normal conditions but, in hotter conditions, feed intake would be reduced and milk yield would fall. [Moore RB, Fuquay JW, Drapala WJ (1992) Effects of late gestation heat stress on post-partum milk production in dairy cattle. Journal of Dairy Science 75: 7, 1877-1882] - Carry-over effects of late gestation heat stress (max. degree-days (>32.2°C) on post-partum productive and reproductive traits were estimated from Daily Herd Improvement records using 341 lactations from 6 sites in Mississippi, USA. Dependent variables included milk and fat production during early-, mid- and late lactation; days to peak lactation; days open; services per conception; and body wt. Degree-days for 60 days pre partum had the greatest negative influence on production variables; its statistical significance was shown in predictions of milk and fat production in early- and mid-lactation. [Muller CJC, Botha JA, Smith WA (1994) Effect of shade on various parameters of Friesian cows in a Mediterranean climate in South Africa. 1. Feed and water intake, milk production and milk composition. South African Journal of Animal Science 24: 2, 49-55] - The effect of a shade structure on the feed intake, water intake, milk yield and milk composition of Dutch-type Friesian cows in a temperate climate was determined over 3 summer seasons: 1984-87. The shade structure reduced radiation as was indicated by lower black globe temperatures. Feed intake of shade cows was higher during 1984/85 and 1985/86) than that of no-shade cows. Regression analysis suggested that day-time feed intake was significantly affected by increasing maximum ambient temperatures. No-shade cows had higher ad lib. water intakes than shade cows (114 vs. 97 litres/day). Water intake of cows on daily maximum ambient temperatures indicated significant increases in water intake of the no-shade cows with increasing ambient temperatures. The overall milk yield of shade cows was 55% higher than that of no-shade cows. High day-time ambient temperature did not affect (P>0.05) average daily milk yield of cows in either treatment. No significant difference was found in milk composition of shade vs. no-shade cows. At prevailing prices and costs the improvement in milk yield resulted in a net return of 42% per annum on the capital outlay of the shade structure. [Muller CJC, Botha JA, Smith WA (1994) Effect of shade on various parameters of Friesian cows in a Mediterranean climate in South Africa. 3. Behaviour. South African Journal of Animal Science 24: 2, 61-66] - The effect of a shade structure on the behaviour of lactating Friesian cows in open camps (dry lots) was determined over 2 consecutive summer periods: 1985/86 and 1986/87. Shade cows spent more time feeding during the day than no-shade cows, while there was no difference in feeding time at night. No-shade cows spent more time standing during the day than shade cows and they also tended to crowd around the water trough. Shade cows tended to spend more time lying down (mainly in the shade) to ruminate or to sleep than cows without access to shade. Different behavioural patterns indicated responses by cows specifically aimed at alleviating heat stress during the day [Murayama S, Kosaka S, Kibushi T (1978) Studies on stand establishment in lucerne swards. 5. Effects of shading treatment on the growth and chemical composition of lucerne. Journal of the College of Dairying 7: 2, 307-320] - In lucerne grown with 0, 60 or 80% shading, leaf number, leaf area, fresh wt. and dry wt. decreased with increased shading. Shading increased growth rate during the vegetative stage and the increase was more marked after 1st flowering. Shading also increased the top:root ratio, decreased growth of top wt., root wt. and total wt., decreased total available carbohydrate content and increased total N content. Shading decreased yields of total N and total available carbohydrate. [Neuworth JG, Norton JK, Rawlings CA, Thompson FN, Ware GO (1979) Physiologic responses of dairy calves to environmental heat stress. International Journal of Biometerology 23: 3, 243-254] -

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During successive exposure of eight Holstein calves to five temperature levels ranging from 15.5°C to 37.7°C at 60% relative humidity (RH), the stroke volume, heart rate, arterial systolic and diastolic pressures, plasma cortisol and thyroxine levels and internal and skin temperatures were measured. It was found that three to four week old male calves respond to acute heat stress only above 32.2°C at 60% RH and do not demonstrate a marked attempt to acclimatize until at least four to five hours of exposure at 37.7°C. [Oliver JC, Hellman HM, Bishop SE, Pelissier CL, Bennett LF (1979) Heat stress survey. California-Agriculture 33: 3, 6-8] - The tropical storm Doreen caused heavy milk production losses in the Chino valley area of California during Aug. 1977. The week following the storm was the main heat stress period when RH approached 100% at night and 50% at midday. 234 dairy farms in the area reported a mortality of 0.5% amongst lactating cows and 0.1% amongst dry cows. Av. daily milk yield dropped from 52.4 to 46.4 lb during the 8-day stress period; milk fat and SNF yields were also significantly reduced. The survey showed that shades were more effective than foggers in reducing production losses and cow deaths during heat stress; wash system (fire hose vs. jet cow washers) and cowshed type (flat vs. herringbone) had little effect. [Peri PL, Bloomberg M (2002) Windbreaks in southern Patagonia, Argentina: A review of research on growth models, windspeed reduction, and effects on crops. Agroforestry Systems 56(2): 129-144] - In Patagonia, where strong winds are a constraint to agricultural production, live windbreaks are often planted in agricultural fields to protect crops, livestock, and soils from wind hazards. A review of the research on the effect of live windbreaks during 1993 through 2000 is presented in the paper. Porosity and distance from windbreak were found to have major effects on relative windspeed reduction. The greatest degree of protection was for dense windbreaks (windspeed reduction of 85%) at 1H (1H = a distance of one tree height, leeward of the windbreak). Different crops showed a differential yield response to wind stress. The production of garlic (Allium sativum) was not significantly affected by wind. Tulip (Tulipa sp.) bulb yield decreased on average by 25% between 2H and 17H. The production of lucerne (Medicago sativa) at 1H was 40% higher than lucerne grown in open conditions. In contrast, strawberry (Fragaria sp.) and cherry (Prunus avium) were more sensitive to the effect of the wind. [Ravagnolo O, Misztal I, Hoogenboom G (2000) Genetic component of heat stress in dairy cattle, development of heat index function. Journal of Dairy Science 83: 9, 2120-2125] - Production data obtained from AIPL USDA included 119337 first-parity, test-day records of 15012 Holsteins from 134 Georgia farms collected in 1990 to 1997. Each test-day record was augmented with weather information from the closest weather station. Analyses were based on models that included effects of herd-year-season, age, test day, milking frequency, and several types of heat and humidity. The best model used a temperature-humidity index. With this model, the average test-day yield for milk was approximately 26.3 kg for a temperature-humidity index <72 and decreased at approximately 0.2 kg per unit increase in the temperature-humidity index for a temperature-humidity index more than or equal to 72. For fat and protein, the test yield was 0.92 and 0.85 kg at a temperature-humidity index <72, respectively, and declined at a rate of 0.012 and 0.009 kg per degree of the temperature-humidity index, respectively. The temperature-humidity index calculated with the available weather information can be used to account for the effect of heat stress on production. [Ravagnolo O, Misztal I (2000) Genetic component of heat stress in dairy cattle, parameter estimation. Journal of Dairy Science 83: 9, 2126-2130] - Our data included 119205 first-parity, test-day records from 15002 Holsteins in 134 Georgia farms with temperature and humidity data from 21 weather stations throughout Georgia. Variance components were estimated by REML. For heat-humidity indices below 72, heritability for milk was 0.17, and additive variance of heat tolerance was 0. For a heat-humidity index of 86 (which would correspond to temperatures of 36°C at 50% humidity), the additive variance of heat tolerance was as high as for general effect, and the genetic correlation between the 2 effects was -0.36. Results for fat and protein were similar. Current selection for production reduces heat tolerance. Joint selection for heat tolerance and production is possible. [Ray DE, Hale WH, Marchell JA (1969) Influence of season, sex and hormonal growth stimulants on feedlot performance of beef cattle. J. Animal Science 29: 490-495] – Gains during the winter in Arizona were 14-24% greater than during summer, and feed requirements were lower by 7-19% during winter. This was attributed to stress from high summer temperatures, probably combined with

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radiation and humidity. The ave. monthly ‘high’ and ‘low’ temperatures ranged from 19.9-41.1°C and 3.3-24.9°C, respectively, with relative humidity at 11 am varying from 22-40%. [Ray DE, Jassim AH, Armstrong DV, Wiersma F, Schuh JD (1992) Influence of season and microclimate on fertility of dairy cows in a hot-arid environment. International Journal of Biometeorology 36: 3, 141-145] - Records were obtained over a 3-yr period from dairy farms each with 300-500 Holstein cows. Calving interval and days open were lowest for evaporation-cooled groups (374 and 98 days, resp.), with no difference between shade only (301 and 112 days) and foggers (392 and 116 days). Number of services per conception did not differ significantly among groups (1.72-1.79). The results showed that evaporative cooling was more effective than fogging for reducing the detrimental effects of high temp. on fertility. [Roman-Ponce H, Thatcher WW, Buffington DE, Wilcox CJ, van Horn HH (1977) Physiological and production responses of dairy cattle to a shade structure in a subtropical environment. Journal of Dairy Science 60: 3, 424-430] - In Florida, on a farm where average daily summer temperature ranges from 24.4 ºC to 27.7 ºC, lactating cows (116) were assigned randomly to shade or no shade treatments during the summers of 1974 and 1975. Shade structure was 9.1 x 24.4 m with an insulated metal gable roof and floor of reinforced concrete. Feed and water were available under the structure, and cows had free access to adjacent bermudagrass sod. Black globe treatment was the climatological response that differed among treatments (shade = 28.4 ºC, no shade = 36.7ºC). Respirations/min (54<82) and rectal temperatures (38.9ºC <39.4ºC) were lower for shade cows. Least squares means for milk yield, considering variability due to treatment, year, treatment-year, breed, breed-treatment, year-breed, year-breed-treatment, cows in year-breed-treatment, week of experiment and days pregnant, were 16.6 and 15.0 kg/day for shade and no shade, a 10.7% effect. Lactation curves were heterogeneous. Conception rates were 44.4% (54 services) and 25.3% (75 services) for shade and no shade. Results suggest improvement in reproduction and lactation from providing shade structure. [Sanchez R, Febles I (1999) A note on the effect of natural shade on milk yield. Cuban Journal of Agricultural Science 33: 2, 135-139] - 10 Holstein cows with 4-5 calvings and in mid-lactation were used to study the effect of natural shaded paddocks on milk yield. Cows were grazed from 16.30 to 05.00 h and from 06.00 to 10.00 h on pure Cynodon nlemfuensis grasslands and were milked twice daily (at 05.00 and 14.30 h). They were kept in pens with water troughs from 10.00 to 16.30 h. Cows were introduced to 1850 m2 paddocks for 14 days. The first 7 days in paddocks with no trees (treatment 1) and the rest in paddocks with 4 Albizia lebbeck trees each (treatment 2) which produced 98.57 m2 of shade. Pasture availability, intake and composition were determined and the values of temperature and relative humidity were recorded. Shade resulted in an increase of 0.9 litres milk/cow daily, but no difference was found in intake and composition of pasture. [Shultz TA, Morrison SR (1987) Manger misting improves dairy cows' appetite. California Agriculture 41: 5-6, 12-13] - A study of dairy cow herds in San Joaquin Valley, California during the summers of 1984 and 1985 monitored cow heat stress on 12 farms with corral manger misters and 12 similar unmisted dairies. Mister systems were teed off corral water troughs and were thermostat-activated at 91°F and timer-controlled for intervals of 5 min on and 5 min off, applying up to 11 gal water/cow daily. Cows were milked twice daily and fed similar lucerne hay, cereal silage and concentrate rations. Feeding areas were on top of concrete-surfaced, gravitational-flow flush lanes. Av. daily milk loss from misted cows was 3 lb less than from unmisted cows. Differences were more apparent for high-yielding cows and during longer heat waves. Benefits were lower in dairies having shade over the manger. Misting also decreased cow mortality after calving and improved subsequent reproduction parameters. Percentages of misted cows eating for 120 min after milking in the afternoon were similar with or without shade, but at unshaded mangers eating was increased by misting. [Silva-Pando FJ, Gonzalez-Hernandez MP, Rozados-Lorenzo MJ. (2002)Pasture production in a silvopastoral system in relation with microclimate variables in the atlantic coast of Spain. Agroforestry Systems 56(3): 203-211] - Orchardgrass (Dactylis glomerata L. cv. 'Artabro') and white clover (Trifolium repens L. cv. 'Huia') are known as shade tolerant and low flammability species that have been successfully used in agroforestry systems in Galicia, both diminishing fire hazard compared with natural shrublands. In this study, annual and seasonal production of a grass mixture of both species was quantified during 3 years in a pinewood under different tree canopy covers. Regardless of

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cover, pasture production increased in summer, and decreased from fall to spring. We obtained a significant correlation between annual pasture production and light transmission through the tree canopy (R-2 = 0.96, P <0.05). Light transmittance through a maritime pine canopy (Pinus pinaster Ait.) was higher than through a Scots pine canopy (P. sylvestris L.), corresponding to 36-57% and 16-21% of full sunlight respectively. The highest herbage production was obtained in no tree stands and the lowest under a P. sylvestris canopy. . Variation in seasonal production was more pronounced in stands without trees, and appeared more uniform when percentage of light intercepted by tree canopy increased. [Silver BA (1987) Shade is important for milk production. Queensland Agricultural Journal 113: 2, 95-96] - Groups of 4 cows were grazed without or with access to shade for 8 wk in an area with daily max. temp. between 24.2 and 31.2°C. Av. difference in milk yield between cows with shade and without shade was 1.45 litres/cow daily but during the hottest week the difference was increased to 2.23 litres/cow. Lactose and SNF content of milk from cows without shade was lower and fat content was higher than in milk from cows with shade. Cows without shade showed signs of heat stress (high respiration rate and tongueing) and had max. rectal temp. of 41.6°C compared with 40.5°C for cows with shade. [Sleutjes MA, Lizieire RS, Vieira RAM, Neves CG (1991) Comparative thermal comfort at dairy cattle facilities at the Federal Rural University of Rio de Janeiro, Brazil. Arquivos da Universidade Federal Rural do Rio de Janeiro 14: 1, 85-95] - A comparison was made between a traditional barn, the natural shade from mango trees, an asbestos roof and an open-air, floored stable for housing dairy cattle. Dry-bulb and wet-bulb temperatures, globe thermometer temperature, wind velocity and solar radiation were recorded over an 8-d period in summer, at 0.90 m from the ground (the average height of a dairy cow flank), and at 10 min intervals. The microclimate in the 4 settings was determined using the following indices: Black Globe Humidity Index (BGHI); Temperature Humidity Index (THI); and Thermal Radiation Index (TRI). According to the BGHI index, the open-air stable was found to be extremely uncomfortable for animals on hot summer days. Shadow, especially ventilated shadow, had a BGHI of 81-82, indicating that with proper management European cattle may withstand the tropical summer and remain productive. According to the THI index, none of the housing types offered any comfort (THI = 81.8); however, since the index does not take radiation and ventilation into account, it is not recommended for determining the microclimate. [Spain JN, Spiers DE (1996) Effects of supplemental shade on thermoregulatory response of calves to heat challenge in a hutch environment. Journal of Dairy Science 79: 4, 639-646] - Holstein and Guernsey calves, housed in hutches, were used to evaluate the complex relationships between external environment, housing microclimate and thermal status of calves. The study was conducted during the summer. Supplemental shade reduced the severity of heat stress experienced by calves that were housed in hutches during the summer. [Stott GH, Wiersma F, Menefee BE, Radwanski FR (1976) Influence of environment on passive immunity in calves. Journal of Dairy Science 59: 7, 1306-1311] - Passive immunity in neonatal calves is influenced by environment. In newly born Holstein calves (108 head) 3 different housing environments (shade, cooled shade, hutch) during hot weather produced differences in body temperature, serum corticosteroids, immunoglobulin IgG1 concentrations and mortality. Calves exposed to the hotter, less desirable, environment responded by having a higher mortality, higher serum corticosteroid concentration and lower serum immunoglobulin IgG1 at 2 and 10 days after birth. [Taylor RB, Higginbotham GE; Wiersma F, Sullivan JL, Gomez Alarcon R, Huber JT (1988) Influence of protein degradability and evaporative cooling on performance of Holstein cows in hot environmental temperatures. Journal of Dairy Science 71: Suppl. 1, 158] - 24 Holstein cows were assigned, based on pretreatment milk production and stage of lactation, to 4 treatments arranged in a 2 X 2 factorial where (A). two levels of protein degradability and (B). shade vs. outdoor evaporative cooling (Korral Kool System) were compared. Diets were 64% concentrate with ground maize plus either soyabean meal or maize gluten meal and all contained 20% CP. Milk yield, milk composition and feed intake were not affected by the source of the protein (29.7 vs. 28.9 kg/day for high and low degradability), nor were respiration rates or body temperatures. Cooled cows produced more milk than shade cows (30.3 vs. 28.3 kg/day) while consuming less feed (21.3 vs. 22.5 kg/day). Cooling

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also reduced respiration rates and body temperatures (75.6 vs. 87.4/min; 38.9 vs. 39.1°C). Differences in heat stress were not sufficient to reduce milk yields on high-protein, high-degradability diets. [Thompson JA, Magee DD, Tomaszewski MA, Wilks DL, Fourdraine RH (1996) Management of summer infertility in Texas Holstein dairy cattle. Theriogenology 46: 3, 547-558] - Data on 118 herds in Texas for which pregnancy data were available were analysed. Shade in the lounging, holding pen and dry cow areas, and fans in the lounging area had positive effects on summer pregnancy odds. Fans in the dry cow area were associated with reduced odds of pregnancy. Sprinklers did not significantly modify the effect of season on pregnancy odds. The strong seasonal decrease in pregnancy odds was less severe on farms that provided shade in the lounging, holding pen and dry cow areas and fans in lounging areas. [Ugarte J, Dominguez I (1977) A comparison between free grazing with artificial shade and control grazing with natural shade for milk production. Cuban Journal of Agricultural Science 11: 2, 139-149] - The response of Holstein cows in mid lactation to 2 grazing systems on Pangola grass (Digitaria decumbens) was studied in an experiment in Cuba with 160 cows on a free-grazing system with uncontrolled access to artificial shade (i.e. open-sided buildings with concrete floor and asbestos/cement roof) or a controlled grazing system with 5 paddocks and stocking at 5 cows/ha with natural shade provided by trees. There was no significant difference in pasture availability, grazing intensity, resting time or grazing intervals between the 2 treatments, or in liveweight change, but daily milk yield was 5.95 litres with controlled grazing and 5.15 litres for the other cows. The effect was ascribed to the greater number of animals in natural shade at successive times during the early part of the day (0800 and 1100 h). [Valtorta SE, Leva PE, Gallardo MR (1997) Evaluation of different shades to improve dairy cattle well-being in Argentina. International Journal of Biometeorology 41: 2, 65-67] - Two elm tree shades and an artificial shade structure were evaluated using black globe temperatures to assess their effectiveness in reducing heat load. The artificial structure consisted of a black woven polypropylene cloth providing 80% shade, mounted on 2.5-m-high eucalyptus posts. It was concluded that: tree and artificial shades produced similar effects. Shading the holding pen with an 80% shading cloth was effective in reducing heat load and floor temperatures, and access to shade in a pasture-based system improved animal welfare. [Valtorta SE, Gallardo MR, Castro HC, Castelli ME (1996) Artificial shade and supplementation effects on grazing dairy cows in Argentina. Transactions ASAE 39: 1, 233-236] - 48 grazing dairy cows in mid-lactation were assigned to each of 8 treatments combining the following factors: protection system (shade vs. no shade), daily feed supplementation (0 vs. 3.5 kg concentrate/cow) and cow parity (multiparous vs. primiparous). The study was conducted during the summer (from December 1990 to February 1991) at Rafaela Experimental Station, Santa Fe, Argentina. Shade was provided using an artificial structure. Cows receiving shade were in a diurnal confinement system with water ad libitum. Shaded cows presented lower afternoon rectal temperatures and respiration rates, yielded more milk and protein, and had higher Na and lower K and urea serum concentrations. Somatic cell count was not affected by shade. Grazing activity was not affected by treatment. [Vermeulen GTJ (1987-88) Heat stress and its effect on milk production, milk quality and reproduction. National dairy cattle performance and progeny-testing scheme. Republic of South Africa. Annual report. Volume 7, 79-101] - From a brief survey of the literature, it is shown that, in dairy cattle, high environmental temp. has little effect on 122- or 305-day milk yield, the effect in early lactation being less than in late lactation when heat stress can result in calves being 3 kg lighter than corresponding calves of cows maintained in shade, and a lower milk yield at the beginning of the following lactation. The effects of heat stress on interval to the postpartum oestrus, duration and intensity of oestrus, duration of the oestrous cycle, pregnancy duration and calving interval and the improvement in these traits due to evaporative cooling, zone cooling, air conditioning and shade are discussed. The improvement in milk yield and reproduction resulting from air conditioning did not compensate for the cost of the equipment. Provision of shade resulted in an increase of 10.6% in daily milk production and a conception rate of 44.4% vs. 25.3 for cattle without shade. The effects of heat stress on feed intake and metabolism and on the incidence of mastitis are mentioned.

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[Wiersma F, Armstrong DV (1985) Shading the feed manger to increase dairy production. American Society of Agricultural Engineers No. 85-4027] - The production benefits of a shade over the feed manger to encourage feeding during hot conditions were evaluated. Shade was provided for all cows feeding simultaneously. A modest improvement in yields, and weight gain was recorded for animal using the shaded manger. However, animal demand indicated that 50% shade cover was sufficient, making its provision economically justifiable. [Wolfenson D, Roth Z, Meidan R, Forsberg M (ed.), Greve T (ed.), Gustafsson H (ed.), Katila T (ed.), Kindahl H (ed.), Ropstad E (2000) Impaired reproduction in heat-stressed cattle: basic and applied aspects. Animal reproduction: research and practice II. Proc. 14th International Congress on Animal Reproduction, Stockholm, Sweden, 2-6 July, 2000. Animal Reproduction Science 60-61: 535-547] - A review. Summer heat stress (HS) is a major contributing factor in low fertility in lactating dairy cows in hot environments. Although modern cooling systems are used in dairy farms, fertility remains low. The dominance of the large follicle is suppressed during HS, and the steroidogenic capacity of theca and granulosa cells is compromised. Progesterone secretion by luteal cells is lowered during summer, and in cows subjected to chronic HS, this is also reflected in lower plasma progesterone concentration. HS has been reported to lower plasma concentration of LH and to increase that of FSH; the latter was associated with a drastic reduction in plasma concentration of inhibin. HS impairs oocyte quality and embryo development, and increases embryo mortality. High temperatures compromise endometrial function and alter its secretory activity, which may lead to termination of pregnancy. In addition to the immediate effects, delayed effects of HS have been detected as well. Among them, altered follicular dynamics, suppressed production of follicular steroids, and low quality of oocytes and developed embryos. These may explain the low fertility of cattle during the cool autumn months. A limiting factor is the inability of the high-yielding dairy cow to maintain normothermia. A hormonal manipulation protocol, which induces timed insemination, has been found to improve pregnancy rate and to reduce the number of days open during the summer. [Young BA, Farrell DJ (1993) Implications of excessive heat load to the welfare of cattle in feedlots. Recent advances in animal nutrition in Australia, pp. 45-50, University of New England; Armidale; Australia] - The physiological basis of excessive heat load and practical means for identifying potential problems are discussed with special reference to dairy and beef cattle feedlots. Suggestions for avoiding unacceptable situations are made.

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Selected shade and shelter abstracts from literature 1972-2002 Cold stress with dairy cattle [Broucek J, Letkovicova M, Kovalcuj K (1991) Estimation of cold stress effect on dairy cows. International Journal of Biometeorology 35: 1, 29-32] - crossbred heifers (Slovak Spotted X Holstein-Friesian) were housed in an open, uninsulated barn with straw bedding and a concrete-floored yard. Min. temp. inside the barn were as low as -19°C. The av. milk yield decreased as the temp. approached these minima. [Frazzi E (2000) New tendencies in housing dairy cows. Informatore Agrario 56: 16, 87-91] - Changes in the conditions in cowsheds in Italy are being gradually introduced, at least for cows in milk. Innovations consist of covered sheds and elimination of the external paddock. In hot weather ventilators and mist blowers keep cows cool, while in cold weather windbreaks in the form of nets or retractable walls keep them warm. All these innovations cost money but bring benefits in raising health levels and so milk quality. [Fujita H, Matsuoka S, Takahashi J, Suzuki T, Fujita T (1982) Changes in metabolism and productive performance of lactating dairy cows in cold environments. Research Bulletin of Obihiro University I. 12: 4, 323-329] - In the 1st trial, 2 Holstein-Friesian cows were in controlled climate chambers for successive periods of 5 days at 10, 0, -10, 0 and 10°C. In the 2nd trial, 3 cows were kept for successive periods of 7 days at 10, -10, 10, -20 and 10°C. The cows were offered wilted grass silage and given concentrate at 30% of daily milk yield. Compared with 10°C, DM intake was about 6% lower at -10°C in trial 1 and 7% lower at -20°C in trial 2; water consumption was decreased at low temp. in both trials. Milk yield was slightly lower at -10 and -20°C than at 10°C but fat and protein contents were higher so that differences in FCM and solids-corrected milk yields were not significant. Ventilation and respiration rates decreased markedly at low temp.; heat production estimated from gas metabolism decreased upon initial exposure to low temp. but then tended to increase. In blood, haematocrit values and concn. of non-esterified fatty acids and sugar tended to increase, especially at -20°C. There were no noticeable differences in the responses to gradual (trial 1) and abrupt (trial 2) cold exposure. [Gregory NG (1995) The role of shelterbelts in protecting livestock: a review. NZ Journal of Agricultural Research 38: 423-450] - When cattle are exposed to cold, wind and rain they stand with their backs to the wind to protect their thermally sensitive faces. They may stop grazing but resume feeding when conditions abate. In most circumstances they can catch up with lost consumption. With spring-calving herds, thought should be given to providing shelter during the dry period when the weather is at its worst and feed is at its lowest. [Hemsworth PH, Barnett JL, Beveridge L, Matthews LR (1995) The welfare of extensively managed dairy cattle: a review. Applied Animal Behaviour Science 42: 3, 161-182] - This review identifies some of the main animal welfare issues in extensive dairy production. Lameness is estimated to affect 5.5 to 14% of cows, although one estimate is as high as 60% on an annual basis. Lameness may be affected by the type and maintenance of the farm track, the patience of the stockperson in handling, and herd size. While calves are relatively cold sensitive at birth, both heat and cold can affect the immune system of calves and adversely affect growth rate of newborn calves. The adult cow is adversely affected more by heat than by cold with effects on both reproduction and lactation; some of the adverse effects on lactation can be obviated by the provision of shade. Nevertheless, a climatic factor often associated with cold is wet weather and this can contribute to lameness. [Holmes CW, Christensen R, McLean NA, Lockyer J (1978) Effects of winter weather on the growth rate and heat production of dairy cattle. NZ Journal of Agricultural Research 21: 549-556] - In New Zealand, shelter was given to one group from 1500 h to 900 h each day in an area sheltered behind walls on 3 sides and roofed on one half that was also bedded with sawdust. The exposed group spent that time behind wire fences away from shelter. Both groups then grazed the same paddock but in separate parts. No other feed was offered. The provision of shelter, in association with a relatively dry ground surface, increased the rate of liveweight gain of the heifers in the 2 years by 3.6 and 7.2 kg per head over periods of 54 and 44 days, respectively. That represents a 19-47% increase (ave. 32%) gain. The estimated feed intake was slightly higher for the exposed group (3.9 v 3.8 kg DM/day). The

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ave. daily temperature (June and July) was 7.4 and 10.2°C in 1976 and 1977, with daily rainfall of 5.6 and 2.9 mm, respectively. Heat production of Friesian bulls and Jersey cows was increased by the climatic conditions on only a few occasions when wind speed was high and rain was falling – conditions that reduced the insulative efficiency of the coat. The authors conclude that wet and windy conditions have the effect of removing virtually all of the insulative properties of the hair coat of Friesian and jersey cattle. Thus, in windy, wet conditions these cows would be subject to a degree of cold stress even at relatively warm temperatures. In such conditions the lower critical temperatures were from 7°C to 24°C for cattle on a maintenance ration. [Kiessling B, Huber S, Lehmann B, Boxberger J, Amon T, Bucklin R (1994) Influence of climatic factors and dimension of open pens on their use by dairy cattle. Dairy systems for the 21st century. Proc. third international dairy housing conference held in Orlando, Florida, USA, 2-5 February 1994. 622-631; American Society of Agricultural Engineers Publication 02-94] - In 3 experimental farms, the use of an open run on dairy farms was investigated with regard to size and weather conditions. The popularity of the run was evident in all investigations. An optional open run should not offer less than 7.2 m2 per cow and that, by increasing the space allocation to 15.0 m2 per cow the extent of use and quality of run usage rose considerably. Of the climatic factors, global radiation had the greatest influence on use. High wind speeds caused considerable reduction in use of the pen; therefore, runs should be provided with a windbreak. [Kisiel R, Iwanczuk, Puchajda Z (1992) Environmental factors and milk yield of cows. Acta Academiae Agriculturae ac Technicae No. 27, 67-78] - The effect of farm building modernization on the physical factors of micro- and macroclimate and economic indexes of production of dairy cattle was evaluated. It was ascertained that the building of windbreaks, reduction of numbers of doors, and sealing and protection of a building from the cold had significantly improved bioclimate (temperature, air humidity and movement, cooling). These improvements caused an increase in milk yield and a decrease in feed requirements. [Kubisch HM, Makarechian M (1986) Effects of shelter on post-weaning performance of bull calves. Agriculture and Forestry Bulletin, University of Alberta, Special Issue, 17-19] - Beef Synthetic, crossbred Hereford and Dairy Synthetic male calves were allocated at weaning to pens with a roofed, 3-sided shelter or to open lots with a windbreak. For animals of the 3 breed types, daily gain during the subsequent 140 days averaged 1.83, 1.63 and 1.63 kg, respectively, in sheltered pens, and 1.79, 1.56 and 1.57 kg in open lots. It was concluded that provision of shelter was worthwhile only for breed types with lower growth rates. [Lehmann B, Nichelmann M (ed.), Wierenga HK (ed.), Braun S (1993) Impact of climatic factors and space allowance on the use of an optional yard by dairy cows in loose housing systems. Proceedings of the International Congress on Applied Ethology held in Berlin, 1993: 442-443] - The influence of climatic factors such as solar radiation and winds, and the amount of space per cow on dairy cows' use of an optional open yard was studied in March and April for dairy cows housed in closed buildings. The highest stocking density in the optional adjacent yard was 180 m2 for 28 cows at the same time - the minimum space requirement is thus 6.43 m2 per cow. The main attraction for the cows was solar radiation, there was a high correlation between the number of cows in the yard and the outside temperature. Use of the yard was negatively affected by winds and draughts and sudden drops in temperature. The cows preferred the sheltered part of the yard. Another trial involving cows housed in open fronted buildings was carried out and it was found that the optional yard was still attractive, the cows spent 19.32% of the day outside. [Lesleighter LC, Shelton HM (1986) Adoption of the shrub legume Leucaena leucocephala in central and southeast Queensland. Tropical Grasslands 20: 3, 97-106] - A survey was conducted in Nov. 1984 to quantify the adoption level of L. leucocephala. The farms comprised 30% of the beef and dairy producers in the survey area. Results showed a low adoption level in terms of area planted and number of growers (6% respondents). Adoption was limited by low level of awareness (only 60% had heard of L. leucocephala), lack of information and high failure rate (65% originally planted area). However, data indicated that by 1986 there would be >10-fold increase in planted area and 3-fold increase in grower numbers. Adoption was greatest in Fitzroy division and by beef producers. Other factors influencing adoption such as property characteristics, attitudes and experiences, and information levels and sources are discussed. High failure rate of L. leucocephala plantings was

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linked to low level use of recommended cultural practices such as seed scarification and inoculation and the many small plantings (71% areas <4.1 ha) that were vulnerable to feral animal damage. [McCarrick RB, Drennan MJ (1972) Effect of winter environment on growth of young beef cattle. 1. Effects of exposure during winter to rain or wind and rain combined on performance of 9-month-old Friesian steers fed on two planes of nutrition. Animal Production 14: 97] – In 3 separate years, steers weighing 192-220 kg were wintered in cattle houses, wind-sheltered roofless sawdust pads or unsheltered roofless sawdust pads. Shelter walls in treatments 1 and 2 were 2 or 2.7 m height. Their intakes of hay and concentrate were equalised within the two planes of nutrition. Liveweight gains on all treatments were similar. The daily mean wind speed varied from 5-30 kph, minimum-maximum temperature range –5 to 14°C, rainfall 260-380 mm and wet days 54-62 out of 140, with frost on 68-90 of those days. Shivering and humped posture was sometimes seen during periods of heavy rainfall but not during cold, dry weather. [McDowell RE, Hooven NW, Camoens JK (1976) Effect of climate on performance of Holsteins in first lactation. J. Dairy Science 59: 965-973] – Within the first 60 days of lactation at Beltsville, MD, high temperatures (>27°C) restricted intake and resulted in rapid utilisation of body reserves and loss of weight. Maximum temperature, minimum temperature and dewpoint (humidity) accounted for almost as much of the variability in milk yield as 12 variables of climate. Cold temperatures stimulated feed intake, resulting in higher yields and gross efficiency than for moderate or high temperatures. After 60 days, feeding level was the primary variable limiting performance, irrespective of climate. The monthly temperature means vary from 6.1- 31.1°C Max T and -1.7- 21.1°C Min.T. [Morrison SR, Givens RL, Garrett WN, Bond TE (1970) Effect of mud, wind and rain on beef cattle in feedlot. California Agriculture 24(8): 6-7] – light wind from fans (0.6-1.5 m/second) had no effect on gains. Water applied from sprinklers at 2 minutes per hour had little effect on gain, although the effect from spraying 10 minutes per hour was almost significant. Mud seriously reduced performance, compared with concrete floors that were cleaned weekly: cattle kept in muddy pens during 3 winters averaged 0.95 kg/day compared with 1.35 kg/day for those on concrete floors. [Muller CJC, Botha JA (1995) Effect of shelter on the performance of Friesian cows during winter in a Mediterranean climate. South African Journal of Animal Science 25: 2, 52-56] - Friesian cows were housed in an earth dry lot without or with protection from the wind and rain (shade shelter 3.5 m high) or in a tie-stall barn with a concrete floor for 53 days during the winter in a temperate climatic zone of South Africa. Cows were fed ad libitum on a complete diet (13.5% CP and ME 9.6 MJ/kg DM). The maximum and minimum temperatures during the trial were 18.5 and 8.7°C, respectively. Total rainfall was 180.6 mm and a daily rainfall of >5.0 mm was recorded on 12 days. DM intake was not related to treatment (21.4, 23.0 and 23.9 kg DM/day for cows in the unsheltered and sheltered dry lot and those in the barn, respectively). Daily milk yield and milk composition did not differ between treatments and plasma cortisol and thyroxine levels were similar. [Scibilia LS, Muller LD, Kensinger RS, Sweeney TF, Shellenberger PR (1987) Effect of environmental temperature and dietary fat on growth and physiological responses of newborn calves. Journal of Dairy Science 70: 7, 1426-1433] - Effects of cold environmental temperature and supplemental dietary fat (energy) on growth rate and physiological responses of young dairy calves fed on a milk replacer diet were studied. Thirty-six Holstein-Friesian bull calves were randomly assigned to 1 of 6 treatments allotted in a 2(-4° or 10°C) X 3(10, 17.5 or 25% dietary fat) factorial arrangement of treatments. Calves began the experiment at an average of 6 days old and received 0.6 kg dry milk replacer in 4 litres of water daily for 3 weeks. Average daily gains for calves given 10, 17.5, and 25% fat diets were -0.04, 0.02 and 0.09 kg at -4° and 0.15, 0.22, and 0.20 kg at 10°C. Gains were significantly lower for calves housed at -4°. Respiratory rates and water intakes were lower for calves housed at -4°C but were not affected by diet. Calves housed at -4°C had higher maintenance energy requirements (0.133 Mcal metabolizable energy/kg0.75) than calves housed at 10° (0.101 Mcal/kg0.75). Consequently, calves housed at -4°C require 32% more energy for maintenance than calves housed at a temperature within their thermoneutral zone. [Serban D, Stamatin T, Gogea G (1985) Optimal organization of summer pasture for cows. Effect of providing shelter. Revista de Cresterea Animalelor 35: 4, 11-16] - An experiment with 2 matched groups of 20 cows that were kept from May to Oct. on cultivated pasture at 240 m altitude showed that

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provision of a cheap, simple shelter for the cows at night had beneficial effects on milk yield, reproduction and physiological indices (rectal temp. and respiration rate). [Shijimaya K, Furugouri K, Ando S (1985) The effects of cold temperature on milk production and some physiological responses of lactating cows fed basal rations of formula feed and corn silage, and hay ad libitum. Research Bulletin of the Hokkaido National Agricultural Experiment Station No. 144, 1-8] - Six cows past peak lactation were divided at random into 2 groups and assigned to a switchback design of three 3-week periods. Cows in the cold group were kept in a wooden barn with open south-facing windows (-1.1°C mean temperature), and the control group was kept in a reinforced concrete barn with double windows (4.9°C mean temperature). All cows were fed on formula feed, timothy hay and maize silage. Hay was given to appetite and the daily allowance of formula feed and maize silage was 40% of the total digestible nutrient (TDN) requirement of the Japanese Feeding Standard for dairy cattle. DM intake of each experimental ration was not significantly different for the 2 treatments. TDN and digestible crude protein (DCP) intakes were 107% of the requirements for both treatments, and there were no apparent differences in TDN, DCP, and net energy intakes. Milk yield, 4%-fat corrected milk yield, and solids-corrected milk yield were 19.8, 19.0, and 18.7 for the cold group and 19.9, 19.1 and 18.7 kg/day for the control group; differences were not significant. The percentages of total solids and solids-not-fat were slightly higher for the cold group than the control group. The respiration rate was significantly lower in the cold group than in the control group but body temperature and heart rate were similar for both treatments. [Webster AJF, JL Monteith (ed.), LE Mount (ed.) (1974) Heat loss from cattle with particular emphasis on the effects of cold. In ‘Heat loss from animals and man’, pp. 205-231. (Publ. Butterworths, London; UK)]. Temperature tolerance depends on breed, the condition of the animal, and husbandry. For instance, cold tolerance is greater in beef cows than dairy cows, in lactating cows than dry cows, and in unhoused than housed cattle. Lower critical temperatures range from 9°C in neonates to -40°C in high-yielding dairy cattle; unhoused cattle in Alberta, Canada, tolerate a wide range of temperatures, +18°C in the summer and -26°C in the winter. Cold acclimation involves increased food intake, reduced shedding of summer coat when the winter coat is grown, a slight increase in thermoneutral metabolic rate, vasomotor control of peripheral circulation, and possible habituation (that is, lowering of the threshold skin temperature which registers a cold sensation). Several points regarding husbandry are discussed: for instance, the chilling effect of mud. In the U.K., shelter from wind and rain will conserve external insulative properties. An open shelter with protection from wind and good drainage, will allow the animals to move freely and select the environment most favourable for radiant exchanges. Heat stress is rare in the U.K. During brief heat stress, a cow's metabolic rate rises, partly owing to the increased work of thermoregulation, and partly due to a Q10 effect. During chronic heat stress, food intake and heat production decrease, and evaporative heat loss increases. [Yamagishi N, Shishido H, Mitsuhashi T, Watanabe T, Kamata T (1984) The effect of a cold climate on lactation. I. The effect of wind at 0°C. Japanese Journal of Livestock Management 20: 1, 58-59] - In a switchback trial with 14-day periods, 8 Holstein-Friesian cows were kept in 2 groups in climate chambers (i) at 18°C and 60% RH (control) or (ii) 0°C with a simulated wind of 2.5 m/s. Both groups were given hay and concentrates to 110% of Japanese standards based on performance before the trial. There was no significant difference among groups or treatments in DM intake or weight change, but intake tended to be higher and weight lower with the cold treatment. Although water for both groups was at 15°C, water intake was decreased by the cold treatment. Daily milk yield (av. 23-24 kg) was not significantly affected by treatment, but av. milk fat and protein were increased by the cold treatment, from 3.3-3.4 and 2.9% to 3.7-3.8 and 3.0-3.1%, respectively. [Yamagishi N, Shishido H, Mitsuhashi T, Otani B (1985) Effect of a cold climate on lactation. II. The effect of feed intake at -10°C. Japanese Journal of Livestock Management 21: 1, 17-19] - In successive periods of 14 days, 8 Holstein-Friesian cows were kept in climate chambers at 18°C and 60% RH (control), and -10°C and 18°C. Cows in 2 groups were offered diets of hay and concentrates supplying (i) 105% of Japanese standards for TDN in each period, or (ii) 105% of standards at 18°C and 125% of standards at -10°C. Because of feed refusals, actual TDN intakes averaged 100.8 and 104.8% of standards in the control periods and 103.5 and 119.6% of standards in the cold period. Milk yield was not affected by treatment, averaging 26-27 and 25 kg/day for the 2 groups respectively. However, the milk yield of lower yielding cows was decreased by 4% in the cold chamber. Milk fat

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(initially 3.2-3.4%) and lactose were increased by 8 and 2% resp. in the cold room, with no significant difference between groups. Milk protein and SNF contents were increased by 5 and 2% in the cold chamber for the cows given the same TDN allowance in both chambers, and by 7 and 3% respectively, for cows given extra energy in the cold chamber; the fat- and solids-corrected milk yields of the latter group increased significantly by 7 and 4% in the cold chamber, whereas the differences were not significant in the case of the former cows.

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Possible implications for dairy production in Victoria Shade There is no particularly convincing argument that dairy cows will respond in economic terms to the provision of shade in southern Australia. Dragovich D (1978) found no significant effect of hot days (>27°C) on production in New South Wales. Neither prolonged periods of high temp. nor the rapid onset of hot weather resulted in consistent declines in farm production. However, acclimatisation of cows to temperatures that were often not greatly above the 27°C threshold, and adequate high quality feed, probably contributed to the lack of response to high temperature. While temperatures often exceed 30°C, at which a response might be expected, the humidity range is generally not high enough to aggravate the situation. The New Zealand evidence (Gregory 1995) indicated that providing shelter from the sun in hot conditions improved milk yield and milk fat yield, while reducing mastitis and increasing conception rates in dairy cattle and growth rates in fattening cattle. He stated that high-performing herds are more susceptible to a rise in THI and so that may be something to be aware of where there are high-producing herds. The results of the Australian survey by Mayer et al. (1999) were as follows:

• The milk production patterns varied among sites, but all showed a general decline as THI increased beyond a certain point.

• The point at which production declined was higher in the tropical and subtropical studies, indicating better adaptation to heat.

• Losses were also greater for herds with above average production levels. Herds with low producing cows showed little effect of heat, even at THI up to 87.

• Applied management - shading and sprinklers – had a THI threshold of 83, about 2 units higher than for similar cows under average conditions.

• Milk fat and protein relationships behaved similarly to milk production. • Reproductive performance was also affected as THI increased, with lower first service

conception rates, more days open and a larger number of services per pregnancy. Mayer et al. (1999) have provided a computer package that might enable managers to estimate the economic cost/benefit of various strategies to alleviate heat stress in their particular region. Whether or not there is likely to be a productive response to shade in southern Victoria remains in question. It is suggested that a small study could be done, using the computer package, in an effort to help resolve the question. If the trend of global warming is maintained then we are likely to experience hotter summers, with possibly greater humidity, and that would make it more likely a productive response to the provision of tree shade will occur. Shelter The effect of cold stress on dairy production must not be neglected, because any increase in maintenance energy needs will affect production or the efficiency of production. However, Muller and Botha (1995) found no significant effect on milk production of shelter from wind and rain on the performance of Friesian cows during winter in a Mediterranean climate in South Africa (maximum and minimum temperatures during the trial were 18.5 and 8.7°C, respectively, and total rainfall was 180.6 mm and a daily rainfall of >5.0 mm was recorded on 12 days). These conditions are probably less severe than might be encountered in southern Australia, particularly where the climate is also more windy. Holmes et al. (1978) investigated the effects of winter weather on the growth rate and heat production of dairy cattle in New Zealand, a situation that may be more akin to conditions in southern Victoria. The provision of shelter, in association with a relatively dry ground surface, increased the rate of liveweight gain of the heifers in the 2 years by 3.6 and 7.2 kg per head over periods of 54 and 44 days, respectively. That represents an average gain of 32%. The average daily temperature (June and July) was 7.4 and 10.2°C in 1976 and 1977, with daily rainfall of 5.6 and 2.9 mm, respectively. Heat production of Friesian bulls and jersey cows was increased by the climatic conditions on only a few occasions when wind speed was high and rain was falling – conditions that reduced the insulative

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efficiency of the coat. Wet and windy conditions remove virtually all of the insulative properties of the hair coat of Friesian and Jersey cattle. Thus, in windy, wet conditions these cows would be subject to a degree of cold stress even at relatively warm temperatures. In such conditions the lower critical temperatures were from 7°C to 24°C for cattle on a maintenance ration. Whether it is economic or not, in terms of increased milk production, welfare considerations will ultimately demand that shelter and shade be provided for dairy cattle. Research in Victoria In 1983, a proposal was made to District Office staff of Department of Agriculture in the dairy areas of Victoria (Warrnambool, Colac, Ballarat, Warragul, Bairnsdale, Leongatha, Maffra, Shepparton, Echuca, Swan Hill) to collaborate in a study to evaluate the direct effects of shade and/or shelter on dairy production. The aim was for each district to try and locate properties that had good shelter and compare these with properties with comparable management but with no shelter. It was hoped to get about 10 sets of data each from several centres. The approach was quite simple and was to involve examination of data retrospectively – principally, daily bulk milk production records from the farms for days during and the day following periods of inclement weather. Oliver et al. (1979) used a similar approach, following a tropical storm that caused heavy milk production losses in the Chino valley area of California during August 1977. Dragovich (1978) used a somewhat similar approach, too. The periods of weather to be identified were tentatively identified as: Type of weather Mean temperature °C Daily windrun (m/sec) Rain 1. Warm, calm, dry days 15-20 <1.5 <1 2. Warm, windy, dry days 15-20 >6 <1 3. Hot, calm, dry days 25+ <1.5 <1 4. Hot, windy, dry days 25+ >6 <1 5. Cold, calm, dry days <10 <1.5 <1 6. Cold, windy, dry days <10 >6 <1 7. Cold, calm, wet days <10 <1.5 >5 8. Cold, windy, wet days <10 >6 >5

The aim was, for a given contrasting periods of weather, to compare the percentage change in production of cows on the sheltered farms over those periods (compared with an average preceding period) with the percentage change in production of cows on unsheltered farms (compared with an average preceding period). Comparison 1 v. 8 would highlight any impact of shelter in reducing cold stress. Another comparison could be 3 v. 1 – looking particularly at the possible impact of shade. The project did not eventuate in 1983. Of the 5 districts from which responses were received, most of the Dairy Industry Officers were interested but regarded it as too difficult, or their superiors regarded it as a distraction, citing following factors:

• very few farms with good shelterbelts could be identified (this appeared to be the major negative factor) as shown by responses from Warragul, Leongatha, Warrnambool,

• complications of differing management among farms, especially where some farmers fed more supplements in periods of bad weather to compensate for perceived stress

• perception that information needed to be collected on individual animals because there may be some difference in numbers over time due to calving, disease or other factors

• perception that differences among paddocks would be a major impediment – were the paddocks really sheltered? Was a difference in performance due to a change in paddock feed?

• perception that the time requirement was high - that no-one had time to spend on the collection of data (Warragul, Maffra)

• reduced district budget (20% cut) preventing any new initiatives (Colac) • doubts about the availability of local weather data (thought not to be close enough) • perception that natural shelter from gullies and creeks was already available (Leongatha)

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All staff who responded did not appear to grasp the essential details of the method of comparison, which is based on relative production. Julian King from Warrnambool had a go in 1992 but was not able to get far, as his preliminary data (2 weeks in August 1992) with a limited number of dairy farms was not very encouraging. Unfortunately, Julian also did not search retrospectively for a suitable period of bad weather, so the lack of substantial effect was not surprising. This approach does depend on extension staff having the time to contact a number of farmers who either have good shelter or do not have good shelter, to form the survey groups. This would involve visits to establish whether the farms were appropriate for the project. A large number of farms, or a large number of periods with a smaller number of farms, would be needed in order to average out the large, inevitable errors associated with such uncontrolled experiments. And it does depend on there being quite large effects that will override the uncontrollable errors. It also needs people with an interest to look carefully at the meteorological record for suitable periods of weather and then seek milk production data from producers records – and, perhaps, follow up with visits to farmers to check on any unusual results (e.g. were the sheltered cows in unsheltered paddocks during that time?). It does not demand any physical work or intervention in the dairy by the farmer. I recommend that, when there are farms with shelter available, this approach should be attempted again, but with a clearer understanding by extension staff of the elements that need to be controlled and those that can be ignored.

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