Volume 5, Number 2 Summer 1997

As the summer monthsapproach, breeder and pullettechnicians and their growersare preparing for the strugglewith hot weather conditions.Achieving and maintaining goodproduction levels during this timeof the year is one of the majorchallenges facing breederdepartments around the world.Allow CVI to visit with youconcerning some key areas ofsummer ventilation that mayease the burden of stress on yourbirds during this year’s season.

High temperatureis only one part ofthe summerequation thatservice staff mustdeal with. Thecombination of thishigh temperaturealong with highrelative humidity isthe critical issue.The heat index(temperature andhumidity factor) iswhat productionpersonnel shouldkeep in mind whenmanaging theirflocks. Heat indexcan be defined as the additionof temperature in fahrenheit andrelative humidity. If, whenadded together, the total ofthese two factors is greater than160, there is a heat index that isdetrimental to bird performance.All chickens struggle in theseconditions, so it is not hard torealize that broiler breeders in

production may be the mostsusceptible to the hot weatherstress.

Tunnel ventilation withevaporative cooling is the mostpopular type of system used forthe control of heat stress onbreeders today. If evaporativecooling systems are installed,maintained, and managedproperly they will provideadequate environments for your flocks.

The first priority of summerventilation is air velocity at bird

level. Air movement is veryimportant to the bird’s ability todissipate heat into theenvironment. The secondpriority is the air exchange ratein the house which is critical tomaintaining adequate oxygenlevels. With evaporative coolingsystems air velocities of threehundred to four hundred feet

per minute (300-400 f.p.m.) areneeded. The ideal velocitywould be 350 f.p.m. through thehouse. The air exchange rateshould range from .75 to 1.3minutes, with 1 air exchangeevery minute being the ideal.

The fan capacity (as requiredto achieve the desired airvelocity and exchange) mustalways be matched with the padspace. Whenever the air speedthrough the pads is too fast theevaporative efficiency will not begood and moisture will be pulled

into the house.Likewise if the airspeed is too slowthen thetemperature dropwill be less thandesired. The airspeed through asix inch padshould be 400f.p.m. and thespeed should be250 f.p.m.through a fourinch pad.However, thesespeeds willcreate only anegative

pressure of .01 - .015 in thehouse. This pressure is notgreat enough to provide uniformairflow throughout the housefrom sidewall to sidewall.

The negative pressure in a forty foot wide house should be .05. To achieve this pressure, air must enter the house at the equivalent

Evaporative Cooling SystemsUnderstanding and Maximizing Summer Ventilation

- by Robert Barnwell

Quarterly Publication of Cobb-Vantress, Incorporated

of 900 f.p.m. A method ofaccomplishing this is using a curtainbetween the pads and house torestrict the inlet space at theentrance to the house. This forcesthe air speed entering the house(after going through the pad at theproper speed) to increase. This isan important point to monitor intunnel ventilation houses. If thesystem is going to achieve adequateefficiency, it must operate at theproper pressure and have air speedentering the house at the propervelocity for the width of the house.

The fan controls should be set tostage their volume up and down withthe temperature changes. It isimportant to remember air velocityand inlet openings must change as fans stage up and down. Thewater pumps should operate onlyafter all the fans have staged on. The pumps should never runcontinuously. The pumps need adual control for temperature andhumidity. It is important toremember that the environmentalchallenge is the heat index(temperature and humidity) not justtemperature. Adding moisture in thehouse by running the pad pumps toomuch works against the goal of thesystem. An important point tomention while talking about the heatindex is staging fans down in theevening or early morning based onthermostats only. Many times theheat index might be high due to

elevated humidity during theseperiods but the temperaturealone may dictate a bank offans to shut off. Rememberthat managing heat stressrequires alleviating both hightemperatures and highhumidity. Air velocity acrossthe birds may still be neededduring the times of day whenhumidity is highest. The onlyway to lower humidity is bycreating evaporation.

Maintenance of theevaporative cooling systems isnecessary to keep efficientoperation. Fan speeds and airvolumes must be monitored. Beltsshould be tight and shutters shouldbe cleaned. At the start of eachseason, a surfactant should be

added to the pump tank. To helpclean the pad pores the pumpsshould be run for four hours withoutair moving through the pads. Oncethis is done, clean the pump tankand begin normal operation. Forlong pad life and also to keepefficiency high, the system shouldbe purged on a regular basis. Theeasiest way to accomplish this isto put a hose bib on the end of thesolids trap. Once a week open thefaucet and draw five gallons ofwater and discard it somewhereaway from the house. If there isnot a solids trap or purge line onyour system there should be oneinstalled before hot weather use.Lastly, it is important to ensure thatthe pads have been installedproperly. If the pad is an odd angledesign, the greater angle must be

down and to the outside of thehouse. If it is installed differently, itwill cause water to enter the houseand a good temperature drop will nottake place.In summary:1) Maintain adequate air speed.Calculate the cubic volume of air tobe moved in the house. Divide thehouse length by the desired airvelocity for the necessary airexchange. Divide cubic air volumeby the air exchange and thenecessary c.f.m.’s of fans neededcan be calculated.2) Air exchange (.75 - 1.3 minutes).3) Temperature drop in the house.Temperature drop with air velocitycreates the wind chill effect andlowers the effective temperature thebirds will actually feel. Ideal effectiveconditions for heavy breeders is 68˚and 50% RH.4) Control of relative humidity. Theremust be a high level of evaporationto control humidity. It takes heat andair velocity to create evaporation.5) House pressure must bemaintained. In a forty foot widehouse, .05 negative pressure isneeded, yet the speed through thepads is based on their thickness.Remember to manage inlet spacewith a curtain.6) Provide proper maintenance.

If you follow these priorities, youshould position your flocks to beefficient producers even in the faceof hot weather stress.

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Table 1

Effective TemperaturesActual Temperature Relative Humidity Air Velocity Feet Per Minute

F C 50% 70% 0 100 200 300 400 500

95 50% 95+ 90 80 76 74 7235 50% 35+ 32.2 26.6 24.4 23.3 22.2

95 70% 101 96 87 84 79 7635 70% 38.3 35.5 30.5 28.8 26.1 24.4

90 50% 90+ 85 78 75 73 7032.2 50% 32.2% 26.6 24.4 22.8 21.1 20

90 70% 96 91 84 81 78 7432.2 70% 35.5 32.7 28.8 27.2 25.5 23.3

85 50% 85+ 80 76 73 70 6829.4 50% 29.4+ 26.6 24.4 22.8 21.1 20.0

85 70% 89 86 81 78 76 7429.4 70% 31.6 30 27.2 25.5 24.4 23.3

80 50% 80+ 76 72 70 66 6526.6 50% 26.6 24.4 22.2 21.1 18.9 18.3

80 70% 83+ 79 76 74 69 6726.6 70% 28.3 26.1 24.4 23.3 20.5 19.4

75 50% 75+ 73 70 68 64 6223.9 50% 23.9 22.8 21.1 20 17.7 16.6

75 70% 78 76 74 72 68 6623.9 70% 25.5 24.4 23.3 22.2 20 18.8

70 50% 70+ 66 65 64 62 6121.1 50% 21.1 18.9 18.3 17.7 16.6 16.1

70 70% 74 69 67 66 65 6321.1 70% 23.3 20.5 19.4 18.8 18.3 17.2

Anytime the air speed exceeds 500 feet per minute the effective temperature begins to increase again instead of decreasing because the potential evaporation rate of moisturebegins to diminish. The moisture begins to move with the airflow instead of vaporizing and allowing for evaporation from the heat source and air velocity. For metabolismfrom feed and water intake the ideal conditions are 50% relative humidity (45%-65% limits) and 68 to 70 degrees F (20 to 21.1C). When the moisture holding capacity of the air reaches dew point an increase in humidity above that will create a heat index, therefore the effective temperature is greater than the actual temperature.

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Six years ago CVI charted acourse towards providingtechnical service to ourcustomers. CVI committeditself “.....to provide thetechnical service and supportneeded to maximize the fullgenetic potential of the Cobb500”. At the time we had tworepresentatives in the U.S.market and one in the SouthAmerican region. In the sixyears that have passed CVIhas formed a technical teamthat is second to none in theindustry. We would like to re-introduce them to you.

Our U.S. customer base isnow split between fourrepresentatives. The domesticteam frequently gets togetherand compares notes onmanagement and equipmentdevelopments to allow theircustomers to stay abreast oftheir rapidly changing industry.The demand for the Cobb 500across the world requiredrapid expansion in ourinternational technical staff.

CVI’s overseasrepresentatives bring theirunique perspectives andexperiences to our groupdiscussions, which allows for abroader base of information.

The CVI Technical Service Team

UNITED STATESJoel Truitt - SW - Siloam Springs

Pete Sbanotto - SW - Siloam Springs

Bob Carlson - SE - Gainesville

Chris O’Brien - SE - Gainesville

CVI has the good fortune to have some very finespecialized technicians on its team.

Dr. Ken Powell’s experienceswith physiology andmetabolism, while atOklahoma State Universityand Hoffman La Roche, areunique to the breedingindustry. Likewise, Dr. ChetWeirnusz also studiedphysiology and metabolism at Oklahoma State whilepursuing his doctorate innutrition. Together thesegentlemen will keep CVI on the cutting edge inresearch and in developingmanagement systems tomaximize the Cobb 500’sgenetic potential.

Jose Manduca - S.A. Tech Mgr. - Brazil

Philip Fausto - S.A. - Brazil

Jairo Arenázio - S.A. - Brazil

P. Hundl - Mexico

INTERNATIONAL

Aziz Sacranie - Asian Tech Manager -Scotland

The CVI Technical Service Team

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About the Author:Robert Barnwell

was born onAugust 9, 1941 inPittsburg, Texas.He was raised ona poultry farm andgraduated fromPittsburg HighSchool, where he was active inFFA, receiving all the FFA awardsoffered. After being president ofthe Texas Young Farmers for fouryears, he was employed byPilgrim’s Pride Corporation forsixteen years where he worked his way up from hatchery,production, feed mill, proteinconversion, and processing tosenior vice president.

After owning a poultry andlivestock distributorship for sixyears, he was regional salesmanager for four years for BigDutchman/Cyclone.

He currently lives in Pittsburgwhere he owns and operates aprivate consulting company,working worldwide on poultry andswine ventilation, production andmanagement.

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Robert Barnwell is thenewest member of our teamand needs little introduction.(He has been traveling theworld for several years helpingproduction personnel improvetheir ventilation systems.) CVIis excited to have Robert joinour group and be available tohelp our customers designhouses and facilities forefficient production, as well astrouble shoot problems whenthey occur.

At CVI, we feel we have atechnical team in place thatwill position us to meet thechallenges we put to ourselvessix years ago. CVI holds firmto the vision put forward at thattime.

SPECIALIZED SUPPORTDr. Ken Powell - DVM - Siloam Springs

Dr. Chet Weirnusz - Nutritionist -Siloam Springs

Robert Barnwell - Vent Specialist -Texas

“Today, our product, services and support are betterthan ever before! Tomorrow, we will be better still.

You (our customer) can hold us to it.”Cobb-Vantress, Inc. • P.O. Box 1030

Siloam Springs, Arkansas 72761(501) 524-3166 • FAX (501) 524-3043