intensively managed rotational grazing systems for irrigated pasture

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Rangeland Management 1994 33

INTENSIVELY MANAGEDROTATIONAL GRAZING

SYSTEMS FOR IRRIGATED

PASTUREDaniel J. Drake1and

James Oltjen2

Harvest of forage from irrigated pas-tures can be distinct, at a given timeand a determined amount. A simplifiedanalogy between the hay grower androtational grazing systems may bemade. The manager of a grazing

system determines when and howmuch plant material is harvested. Themanager uses livestock instead ofequipment to make the harvest.

Just as the hay grower must under-stand plant growth principles, themanager of grazing livestock mustunderstand pasture growth principles.These must be balanced with knowl-edge of and performance goals for thelivestock. The objective of the grazingmanagement plan is to quickly anduniformly harvest the desired amount ofplant material. Plans, however, shouldbe considered as guidelines and remainflexible.

A practical intensively grazed pasturesystem consists of a number of pas-tures or paddocks. Pastures aregrazed for one to four days, with someperiod of rest between grazing. Auniform harvest with minimum selectiv-ity and repeated defoliation is encour-

aged when pastures are properlystocked and short grazing periods areused. The manager determines thenumber of livestock per paddock, theamount of time spent grazing on eachpaddock and the amount of time (rest)between grazings. That is, livestockare managed to conduct a timely,uniform and prompt harvest of pasturemuch like a swather for making hay.

Figure 1. Grazing should harvestplant material leaving 2-4

inches. The residual

serves as the basis forregrowth of new plantmaterial for subsequentgrazing.

Intensive grazing systems can be oneof the most cost effective managementactivities for pastures. However, to besuccessful, plant varieties, composition,fertility, and water management mustbe considered.

STOCKING RATES, GRAZING

INTENSITY AND DURATION

Uniform removal of plant material frompasture is encouraged by using arelatively high density or number oflivestock per unit area (acre) of pasture.Picture a mass of cattle moving througha pasture, cutting (grazing) as they

move. Typically, the ideal number oflivestock will remove the desiredamount of pasture in at least 3-4 daysof grazing. When livestock are left tograze a pasture for greater than 3-4days, regrazing of plants previouslybitten will occur. The result is areas ofovergrazing, which selectively discour-ages desirable plants while encourag-ing undesirable plants.

Grazing should remove aportion of the plant whileleaving some leaves tocapture sunlight for theplant to use in growing newleaves. The new leaves orregrowth will be removed insubsequent grazing afteran adequate period of timefor regrowth. Typicalrecommendations are toleave about 2-4 inches ofplant leaves for the plant touse in regrowing. There-

fore the amount of materialavailable for grazing is allof the plant taller thanabout 2-4 inches (Figure 1).

It would be much simpler to planrotational grazing systems, if anaccurate and rapid method existed forestimating the total amount of plant

Available for Grazing

2-4"


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material to be removed by grazing. Adevice marketed as a Pasture Probe1

is adequate for making gross estima-tions. With experience, which thePasture Probe can accelerate, growerscan visually estimate amounts of plant

material for grazing. In the Spring,improved pastures of fescue or orchardgrass with some clover can typically begrazed when about 12 inches or taller.

The number of cattle per acre is bestestimated as a weight relationshiprather than number of head. For cowsand calves the combined weight of cowand calf should be used (1). Forexample, about 15,000 (typical range is15,000 to 25,000) pounds of livestockper acre are generally satisfactory

when the duration of grazing is about 3days. For cattle weighing 600 poundeach, then 25 individuals (15,000divided by 600) per acre would prob-ably be satisfactory. If a paddockconsisted of 5 acres then a total of 125cattle (25 X 5), each weighing 600pounds would be grazed for 3 days.Similarly if the cattle were cows withcalves and their combined weight was

1350 pounds each (ex. cows 1100 plus250 pound calves), then each acremight be grazed with 11-12 cows withtheir calves (15,000 divided by 1350). Ifthe calves had been born in the Fall andweighed perhaps 400 pounds by the

start of the grazing season we woulduse 1500 (1100 plus 400) pounds as theweight of an individual unit (pair). Thus,only about 10 pairs with larger Fall borncalves might be grazed on each acre.

These examples are illustrated in Table1 and your plans can be started in thespace provided. This table providesinformation on management of onepasture or paddock that will be grazedfor only 3 days at one time, we nextneed to consider additional paddocks for

the entire grazing system.

There is no correct number of pad-docks in a grazing system. For practicalreasons eight paddocks is a reasonablecompromise: fewer paddocks will resultin overgrazing or inadequate restbetween grazings, while more paddockscan increase performance of the pasturesystem, but requires considerably

greater labor with smallerincremental returns.

Eight paddocks, when usedwith a rotational grazingscheme of 3 days ofgrazing on each paddock,results in rest periods of 21days. This meets minimumtypical rest recommenda-tions of 21 to 30 days.Typically in the Spring therancher is anxious to startcattle onpasture as earlyas possible, but pasturemay be a little shorter thandesired. Grazing plans canbe adjusted slightly by

AAAAA BBBBB CCCCC DDDDD EEEEE FFFFF GGGGG HHHHH

Total Number of Size in Weight of Desired Total Total Total

Acres Pastures Acres of Individual Weight Number Number of Number

Available (Paddocks) a Single Unit Per of Units Units (Ds) of Units

Pasture or Pair, Steer, Acre (Ds) on for a Single (Ds) for

Paddock etc. 1 Acre Pasture or all Land

Paddock Available

(A

B) (E

D) (F x C) (G)

40 8 5 600 15,000 25 125 125

40 8 5 600 25,000 41-42 205-210 205-210

40 8 5 1100 15,000 13-14 65-70 65-70

40 8 5 1100 + 400 15,000 10 50 50

Your Values

Table 1. The number of livestock for a single pasture or paddock of agrazing system (collection of pastures used in a rotational grazingplan) can be based on the desired weight of beef per acre ratherthan the number of head. Typical weight per acre is from 15,000 to25,000 pounds of beef per acre (column E). The "density" ornumber of livestock to be grazed in a single pasture is calculatedin column F.

1Design Electronics,Palmerston, New Zealand.Available for demonstrationpurposes from some Coop-erative Extension offices.


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leaving the cattle for only 2 days in thefirst paddocks. This will provide enoughforage for the cattle and not overgrazethe pasture. Then with rapid Springgrowth, pastures grazed later will havemore than enough forage for 4 days of

grazing. The combination of grazing for2, 3 or 4 days, depending on forageavailability will result in adequate rest toreturn to the first paddock with at least21 days of rest.

Due to hotter weather after about theFourth of July, pastures typically regrowless rapidly. The grazing manager hasseveral alternatives for adjustment tothis change in plant growth.

1. Reduce the number of livestock,

adjusting for specific pasture growthconditions.

2. Stock slightly low (for the Springperiod) from the beginning, butadequate for the hotter, summerseason. Some extra feed may buildup on the pasture to permit extendinggrazing periods to 4 days after theFourth of July. This would result inrest periods of 28 days.

3. Provide supplemental feed.4. Stock adequately for the summer

season and during rapid Spring

growth do not graze or reducegrazing to create an extra bufferpaddock. This can be grazed duringperiods of slow plant growth. Thisbuffer paddock might be hayed inJune and allowed to regroup for alater grazing period.

Option 1 can be very effective in in-creasing total carrying capacity butrequires more flexibility. Many manag-ers select option 2.

FLEXIBILITY AND

ADJUSTMENTS

Intensive grazing management plansshould be flexible. The following areobservations from some managersuseful for making beneficial adjust-ments. If hard, dry cow patties seem

to be accumulating, it is frequently asymptom of low stocking density.More livestock per acre will tend tobreak up or reduce the occurrence ofcow paddies. Another alternative toreduce manure accumulation is

irrigating immediately after grazing.This is not always feasible.

Another symptom of low stock densityis the appearance of pastures that aregetting ahead of the cattle. Forage isstill tall after the planned three (3) daysof grazing, or the plants are beginningto mature as evidenced by developingseed heads. Solutions are to increaselivestock density, increase grazingduration on the pasture or mechani-cally cutting the excess. The excess, if

practical, might be baled. Increasinggrazing duration is only a temporarysolution since the result is more daysof growth on the next pasture whichwill result in even more excess foragewhen it is grazed. If the excess isgreat enough a hay cutting might betaken instead of grazing that pasture.

FACILITIES

Pastures of approximately the same

size work much better than unequalsized pastures when used in a rota-tional system. Sometimes instead ofthinking how to divide pastures intoeight units (or whatever number areplanned), one needs to consider whatexisting pastures can be grazedtogether to make eight units. Fre-quently 3-4 existing pastures can beeasily split into two or perhaps threepastures each, making a total of 8units.

Figure 2 shows a typical layout. Twowater troughs provide drinking waterfor all 8 pastures. Perimeter fencingcan be barbed wire or newer style hightensile smooth wire fence. Smoothwire fence may be built to provide forelectrification. It should be fourstrands with alternating charged andnon charged (grounded) wire. Interior


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fencing can be multiple strands ofsmooth wire, or a single strand ofsmooth wire or woven plastic/metal wire,commonly marketed as Polywire or the

equivalent. Limited experience sug-gests the wider Polytape is more visible,but may be less resistant to deteriora-tion than Polywire.

Chargers should be high voltage (about5,000) but low amperage - NewZealand type. These are very resistantto grounding out. The most importantaspect of the energizer is adequate andproper grounding. If the fence does notwork, always check the ground first.

Fence posts can be wooden or metal Tposts with insulators, or nonconductingposts such as plastic or special noncon-ducting wood, such as ironwood. Singlewire interior fencing can use short,plastic tred-in posts that are easilymoved. In addition, they are short andflexible enough for wheel lines to moveover them.

A wide variety of fence posts are nowavailable for specific installations suchas pivoting types for center pivotirrigation systems, and tumble wheels,

which facilitate moving.

When livestock drinking water is sharedby numerous pastures, as shown inFigure 2, sacrifice areas or areas ofheavier use occurnear the water. In theillustration in Figure 2 for paddocks 5,6, 7 and 8, this sacrifice area is mini-mized. The design does not requireadditional water development. How-ever, due to the small portion of thewater trough available, adequate flow

to quickly fill the tank should be avail-able. The inset illustrates for paddocks1 and 2 an alternative arrangement thatincreases trough space but suffers froma larger sacrifice area. A single troughis shared by paddocks 1 and 2 with thefence being moved to permit fuller useof the trough. The manager wouldhave to weigh these various conse-quences for each application.

10"

10"

10"

16"

+

-

+

-

A

B

Enlargement

1 2 3 4 5 6 7 8

Figure 2. Aerial view of paddocks showing possible fencing arrangement andalternatives. Inset details electrification pattern for electric fence.

Typical CattleElectric FenceDesign

Alternative temporary fence positions at watersource. When using paddock 2, move fence topoint B.


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IRRIGATION

Besides drinking water, irrigatingintensively grazed pasture systems isthe second major difficulty. Fencingand grazing management strategies

should be designed with existingirrigation systems in mind. With rapidcattle rotation and typically morefencing, irrigation can be difficult.

Irrigation systems should be designedand operated to provide adequateamounts of water in a timely manner.Amounts required can be closelyestimated by using evapotranspiration(ET) information. ET data estimatesthe amount of water used or lostthrough evaporation from soil and

transpiration of plants. Historical datafrom many locations is available andcurrent season data may be availablethrough your land grant university orlocal Cooperative Extension office.Adequate irrigation will insure water isnot a limiting factor in crop productionand resultant grazing potential.

Rotational grazing can be accomplishwith either sprinkler or flood irrigation.It is usually not recommended toirrigate while cattle are on a pasture.

However if this has been a historicaland acceptable practice, it could becontinued with rotational grazing.

Wheel line sprinklers usually cannot beused when the lines are perpendicularto fences creating physical barriers tocattle movement throughout thepaddocks. Wheel lines parallel tofences can be moved over fencing andare compatible with rotational grazing.Center pivot irrigation systems with

their high supply lines can be used inconjunction with break over (pivoting)fence posts.

Regardless of irrigation system, manygrowers attempt to irrigate immediatelyafter grazing. This may facilitateregrowth and certainly appears toreduce or eliminate any fecal deposits.The critical factor is to design the

grazing system to work in conjunctionwith the irrigation system: during thegrowing season provide irrigation tosatisfy crop needs, thereby avoidingwater as the limiting resource.

CATTLE SELECTION AND

MANAGEMENT

No specific breed restrictions apply tointensive grazing systems. Breeds withBrahma influence can be used suc-cessfully, although extra care to avoidtheir agitation maybe important. Aswith set stocking, steers and heifers aretypically not grazed together; however,from the grazing response standpointthis is not a problem. Similarly large

differences in animal weights should beavoided, but no more so than with othergrazing management schemes.

Some grazing managers have foundwhistling or making some distinctivesound when moving cattle leads to alearned response. Cattle will betrained to move when the sound isrepeated.

Ideally cattle should be trained to anelectric fence before putting them onpasture. The only reason for this is toavoid the possible labor involved ingathering cattle if they should break afence. An ideal time to train cattle iswhen cattle are confined in a wellenclosed area. A short strip of electricfence can be constructed, perhapsacross a corner of a familiar corral, anda small amount of hay placed on thegroundon the opposite side of theelectric fence. As the cattle smell thehay they will get acquainted with the

electric fence. This will not harm cattleand they will learn about electric fencesin a controlled and safe manner.

The manager of intensively grazedcattle needs to decide who is makingthe decisions, the cattle or the man-ager. If an individual animal is causingsignificantproblems, will managementbend to the whims of that individual or


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will the manager put that problemsomewhere else and get going with theprogram?

ANIMAL HEALTH

Several considerations should be takento maintain acceptable animal healthlevels when planning rotational grazingsystems. When livestock are managedto more completely utilize pasture, thepotential for grazing of harmful plantsoccurs. As management encouragesmore complete utilization livestock mayconsume plants previously avoided.

Potentially increased density of livestockper unit area may also increase the risk

of internal parasitism and transfer ofcontagious diseases. However, specificanimal behavior with any grazingsystem may result in time periods orareas of high livestock concentration,that are conducive to disease transmis-sion. Preventative measures should beadopted.

ECONOMICS

Rotational grazing management planswhich include length of grazing, restperiods and other factors ultimatelyimpact stocking rates and economics.Considerable evidence indicates as

stocking ratesincrease, suchas may occurwith moreintensiverotationalgrazing, dailygain of indi-

vidual cattledecrease. Thisresponse hasbeen describedas linear (seeFigure 3). Bydefinition thisresponse toincreasedstocking rates

when converted to gain per area iscurvilinear (Figure 3). These trends aretheoretical representations in the graphand specific values and relationshipsvary.

It is noteworthy to recognize that gainper acre does decrease when stockinglevels go beyond some high stockinglevel. Also illustrated on the graph isthe relationship between stocking rateand net returns. This is again a curvi-linear response. With traditional stock-ing rates and economics, net return peracre peaks at lower stocking levelsthan gain per area. However, this mayvary with changes in economics.

Record keeping should permit evalua-

tion of performance for both livestockand pastures. Data collected shouldpermit calculation of amount of live-stock gain per acre, daily gains perhead, stocking rates, and net returns.Supplemental feeds or additional hayproduction should also be included.

An example worksheet illustrates thetypes of information and calculationsuseful for either planning or evaluatinggrazing systems.2 It is important tounderstand differences in evaluating

alternatives on a per head or per acrebasis. Livestock performance hastraditionally been evaluated on a perhead or individual basis. Grazingsystems should also include monitoringand evaluating of land based values.

The computer program facilitates thecomparison of alternative grazingstrategies. It provides both a per headand per acre value for data. Addition-ally, the computer program providessome measure of risk and allowsconsideration of alternatives to alter orreduce risk.

Figure 3. Theoretical responses to stock-ing rate.

1000

800

600

400

200

0

-200

-400

0.5 1 2 3 4 5 6Poun

dsorDollars

Gain per Acre

Gain per HeadNet Return

Stocking Rate, Head per Acre2The computer program for IBM and

compatible computers is available from

Dan Drake, University of California,

Cooperative Extension, 1655 So. Main,

Yreka, CA 96097; (916) 842-2711.


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SUMMARY

Rotational pasture grazing systemscan significantly increase carrying

capacity or production of beef peracre compared to continuous or lessmanaged systems. Rotationalsystems utilizing livestock for grazingcan be implemented to mimic hayharvest with equipment: leading totimely, uniform and planned harvestof pasture plants. Successful planswill incorporate both plant andlivestock concepts to achieve desiredpersonal, economic and environmen-tal goals.

REFERENCES

1. Aiken, G.E. and D.I. Bransby.1992. Technical Note: StockingEquivalents and Stocking RateGain Relationships for Steers andCow-Calf Pairs Grazing OversownBermudagrass. J. Anim. Sci.70:3234-3237.

2. Grazing Research: Design,Methodology and Analysis.1989. Ed. G.C. Marten. CropScience Society of America,Special Publication Number 16,Madison, WI.

3. Smith,B., P. Leung and G. Love.1986. Intensive Grazing Man-agement: Forage, Animals,

Men, Profits. Yu Luen OffsetPrinting Factory Ltd., Hong Kong.

141 Stocker Cattle Profit or Loss and Risk Calculator by142 Version 9.25.91 Daniel J. Drake143.144 Name: Intermountain Example, Typical Stocker Cattle145 Date: 11/11/92 INFO

146 SUPP-147 Comments: LIED CALCULATIONS148149 GENERAL INPUTS AND ASSUMPTIONS Pessi- Opti-150 mistic mistic151 Size of pasture, acres : 40

152 Number of cattle : 80153 Days on feed, total : 150154 Purchase weight, lbs. : 500155 Expected purchase price, $/cwt : 90156 Purchase price variability, % : 10 99.00 81.00157 Expected selling price, $/cwt : 83158 Selling price variability, % : 15 70.55 95.45159 Daily gain, lbs/head : 1.67160 Gain variability, % : 10 1.50 1.84161.

162 PASTURE INPUTS Per Per163 Head Acre Total164 Rent $/head/month : 9 45.00 90.00 3600.00165 Land, taxes, other $/acre : 0 0.00 0.00 0.00166 Land, taxes, other Total $ : 800 10.00 20.00 800.00

167 Irrigation Costs168 Water costs, $/acre foot : 18 20.25 40.50 1620.00169 Water amount, acre feet/acre : 2.25170 Fertilizer Costs171 Amount, Ibs/acre : 300172 Cost, $/ton : 125 9.38 18.75 750.00173 Spread charge, $/acre : 5 2.50 5.00 200.00174 Labor cost, $/month : 200 12.50 25.00 1000.00175.

176 MANAGEMENT INPUTS177 Vet & Medicine, $/head : 5 5.00 10.00 400.00

178 Supplement179 Lbs./head/day : 0.25180 Cost, $/ton : 398 7.46 14.93 597.00

181 Days fed, all = 150 : 150182 Death loss, % : 1 4.55 9.10 364.00183 Yardage, $/head/day : 0.05 7.50 15.00 600.00184 Transportation, $/head : 1 1.00 2.00 80.00185 Brand insp., Beef pro., $/head : 1.9 1.90 3.80 152.00

186 Insurance, Misc. $/head : 0 0.00 0.00 0.00187 Comm., % of buy cost : 0.75 3.38 6.75 270.00188 Comm., % of sell income : 3 18.69 37.37 1495.00189 FINANCIAL INPUTS190 Equity, $/head : 75 75.00 150.00 6000.00191 Cattle interest rate, % : 12 18.49 36.99 1479.45192 Op. Capital interest, % : 11.25 3.44 6.88 275.37193 CME Livestock Options

194 Put Option strike price, $/cwt : 0195 Option Cost cents/lb : 1.2 0.00 0.00 0.00

196 Basis : -2.25197 Number of contracts 44,000# each : 0198 Commission, total $ : 0 0.00 0.00 0.00199 Critical Profit (1), $ total : 30000200 Critical Profit (2), $ total : -2000201.202.203.


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204 R E S U L T S

205 EXPECTED Per Per206 Head Acre Total207 Cattle cost, total 450.00 900.00 36000.00208 Cattle equity, $ 75.00 150.00 6000.00209 Cattle interest, $ 18.49 36.99 1479.45210 Pasture cost 99.63 199.25 7970.00211 Management cost 71.41 142.82 5712.82212 Pasture & Management Cost 171.04 342.07 13682.82213 Pasture, Manage. & Cattle Cost 621.04 1242.07 49682.82214 Gain over total period, lbs. 250.50 501.00 20040.00

215 Total cost per lb. gain 0.68 1.37216 Selling weight, Ibs 750.50 1501.00 60040.00217 Total dollar receipts 622.92 1245.83 49833.20218 Total receipt minus cattle cost 172.92 345.83 13833.20219 Profit or loss 1.88 3.76 150.38

220 Breakeven sell price, $/cwt (cost of prod.) 82.75221 Return on equity, % 2.51222 Breakeven buy price, $/cwt 90.38

Cooperative Extension1

Siskiyou County

Department of Animal Science2

University of California

Davis, CA 95616


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FROM:

California Ranchers' Management Guide

Steven Blank and James Oltjen, Editors.California Cooperative Extension

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intensively managed rotational grazing systems for irrigated pasture

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