Progress 10/01/01 to 09/30/06
Outputs
We have completed several studies to reduce environmental stress of cows raised commercially. Our first study addressed the problem of pneumonia which commonly occurs in indoor calf nurseries where high levels of ammonia, methane, dust, and microbes reach high concentrations. We designed and modeled a ventilation system for calf nursery confinement housing, incorporating a unique polyethylene duct to provide even distribution of filtered air throughout the nursery. In a 3-year study the calves reared in the nursery had a low incidence of pneumonia and no deaths. Cattle wintering in commercial feedlots in CO have lower daily gains than in the summer, but do not differ appreciably in feed intake. We investigated this problem by measuring the rate of heat loss through winter pelts using our laboratory calorimeter. It was determined that the extra heat lost to a clear sky, common in CO, accounted for a 0.3 kg lower daily weight gain than under a cloudy sky. Using this
experimental setup, wetting the summer pelts under low air velocity increased heat loss more than 100 percent compared to dry pelts under still air. This dramatic increase in heat loss prompted us to investigate the importance of sprinklers and fans for dairy cows during hot weather. Wetting the hair coat and increasing air flow over it dramatically increases heat loss from dairy cows' skin in commercial facilities during hot summers. Evaporation rates under a wide range of fans, sprinklers and shade have been measured utilizing our portable calorimeter through a range of hot and dry climates (AZ) to hot and humid (HI and MS). Even in hot or humid environments sprinkling cows immediately cooled the dorsal surface and lowered respiration rate. Core temperature was lowered at a rate of 0.5C/hr when cows were wetted every 20 min at airflow of 2.2 m/s, while core temperature rose at a rate of 0.2C/hr with no wetting and no fans. Either wetting every 20 min. or raising airflow to 2.2 m/s
increased heat loss by 7 times, while combined, heat loss is increased by 14 times. Given the effectiveness of water sprinkling, we designed two systems that would only spray cows while lying in stalls to avoid wetting the bedding, which might increase bacterial growth and may result in mastitis. The spray systems effectively cooled cows without wetting the bedding. By continuously monitoring the core temperature (using a vaginal-temperature logger we developed) of unrestrained dairy and beef cows, cows lost more heat standing than lying down, because lying down reduces the evaporative surface area. When the core temperature of a lactating Holstein cow reaches 38.9C, the cow either stands under a fan without water spray to arrest the rise in body temperature or stands under water spray and fan to lower its body temperature. We investigated the advantages of shade in feedlots and found out that cows with black hair coat, more absorber of solar radiation than white hair coat, were able
to maintain the same core temperature by sweating more. When shade is available, black cows seek shade more than white cows. Heat gain increases with increasing air temperature, hair thickness, and wind velocity.
Impacts
The heat wave in California this past summer was devastating to the dairy industry. According to Andy Zylstra, President of the California Dairy Campaign, 25,000 dairy cows died because of heat stress (temperatures reaching above 100 F) since July 14, 2006. This loss is equivalent to 1,500 to 2,500 dollars per head or between 37.5 to 62.5 million dollars. Milk production in central California was also down where losses are estimated to exceed 200 million dollars. Although the California heat wave was particularly newsworthy, the impact of summer heat on dairy cows has been an ongoing problem where it has been estimated that the US dairy industry looses up to nearly 900 million dollars annually due to heat stress. In July 1995 a heat wave in Iowa resulted in the loss of 3,750 beef cattle. In economic terms this amounts to 42.8 million dollars. Our simultaneous measurements of physiological responses and environmental measurements of heat-stress in dairy and feedlot cows
are necessary for validating mechanistic models, which in turn are used for optimizing management strategies. In doing so, our studies can help reduce economic losses and improve the well-being of cows exposed to heat stress environments.
Publications
- Lee, C.N., Hillman, P.E., Collier, R. and Gebremedhin, K. 2006. Physiological responses of Holstein cows (white or black hair coat) under different solar loads: An environmental chamber study. J. Anim. Sci. Vol.84, Suppl 1/J. Dairy Sci. Vol. 89 Suppl.1 p. 212
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Progress 01/01/05 to 12/31/05
Outputs
Thermal analysis and behavioral activity of heifers in shade or sunlight. Impact of sun and shade on the thermoregulatory responses of four genotypes of feeder cattle was investigated. The genotypes represented four hair coat colors: black (Angus), white (Charolais), tan (MARC-I) and dark red (MARC-III). The haircoat of black Angus absorbs 98 percent of sunlight, while the dark red MARC-III absorbs 92 percent, the tan MARC-I absorbs 75 percent and the white Charolais absorbs 37 percent. The hair coat of black Angus is thinner and finer than the other breeds. Under full sunlight and a THI of 80 to 83 all breeds were able to maintain body temperatures of about 38.6 C. Although Angus absorb more solar energy than Charolais, they offset this gain by sweating more. When shade is available, heifers with hair coats that absorb more solar radiation seek shade more than those that absorb less. Angus seek shade 87 percent of the time, MARC-III 80 percent of the time, MARC-I 62
percent of the time, and Charolais 50 percent of the time. Heifers lower their body temperature at a rate of 0.13 C/hr when standing in the sun or by 0.17 C/hr when standing in the shade. Heifers' body temperature rises by 0.42 C/hr when lying in the sun or by 0.29 C/hr when lying in the shade. A mechanistic coupled heat and mass transfer model that uses environmental parameters and physical and optical properties of hair and hair coat as input was used to do thermal analysis. The model predicted no significant difference between breeds for heifers in shade or sunlight at ambient temperature of 36 C, which is consistent with observations. The model shows that sensible heat gain increases with increasing air temperature, hair thickness, and wind velocity. Microclimate selection and body temperatures in heat-stressed Holsteins vs. heat-stressed Jerseys. An ongoing collaborative project (NY, HI, MS) was conducted during July 2005 at the Mississippi State University Dairy Research Center
in Starkville, MS. Ten Holstein cows and ten Jerseys were equally divided into two groups. The following activities were recorded: lying, standing up, under spray cooling, chewing starts under spray, feeding, and standing in alley. Spray cooling was located away from the feed line on the other side of the barn so that feeding behavior could be separated from spray cooling behavior. Vaginal temperatures loggers were placed in all 20 cows to continuously monitor body temperature. Body weights and body condition scores were taken immediately after the experimental trial. Milk production was recorded at each milking. Air temperature and relative humidity within the barn were recorded. Presently data from this study are being analyzed.
Impacts
In July 1995 a heat wave in Iowa resulted in the loss of 3,750 cattle. In economic terms this amounts to 42.8 million dollars. To avoid such losses, this study evaluates the benefits of shade for feedlot cattle in hot environments. In particular, the impact of direct sunlight on body temperature and thermoregulatory behaviors are identified. It has been estimated that the US dairy industry losses up to nearly 900 million dollars annually due to heat stress. By continuous monitoring of the body temperature matched with behavioral observations of cattle we can better understand their behavior and physiology in commercial facilities during periods of heat stress. In doing so, these studies can provide management strategies to help reduce economic loss and to improve the well-being of cows exposed to heat stress.
Publications
- Gebremedhin, K.G. and B. Wu. 2005. Simulation of flow field of a ventilated and occupied animal space with different inlet and outlet conditions. J. Thermal Biology 30(5):343-353.
- Hillman, P.E., C.N. Lee, and S.T. Scott. 2005. Thermoregulatory responses associated with lying and standing in heat-stressed dairy cows. Transactions of the ASAE. 48(2):795-801.
- Hillman, P.E., K.G. Gebremedhin, T.M. Brown-Brandl, and C.N. Lee. 2005. Thermal analysis and behavioral activity of heifers in shade or sunlight. Proceedings of the Seventh International Livestock Environment Symposium May 18-21, 2005, Bejing, China.
- Jiang, M., K.G. Gebremedhin and L.D. Albright. 2005. Simulation of skin temperature and sensible and latent heat losses through fur layers. Transactions of ASAE 48(2):767-775.
- Zhou, M, A. M. Parkhurst, P. E. Hillman, and C. N. Lee. 2005. Modeling the body temperature of heat stressed lying Holstein cows under two different cooling processes. Proc. 17th Annual Kansas State University Conference on Applied Statistics in Agriculture. Kansas State Univ., Manhattan, KS. (accepted)
- Gebremedhin, K.G. and B. Wu. 2005. Simulation of flow field of a ventilated and occupied animal space with different inlet and outlet conditions. Proceedings of the Seventh International Livestock Environment Symposium May 18-21, 2005, Bejing, China.
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Progress 01/01/04 to 12/31/04
Outputs
Skin temperature may act as a stimulus on animal performance during heat stress. A mechanistic model was developed to predict the skin surface temperature, temperature profile though the fur layer, and sensible and latent heat fluxes at the skin surface for realistic environmental conditions. Sensitivity analyses were conducted to determine effects of different environmental factors and fur properties. The skin surface temperature increased with increasing ambient air temperature, solar load, hair density and thickness of hair coat, but decreased with increasing wind speed. When the skin was considered to be wet, the skin surface temperature increased with increasing relative humidity, and evaporative heat loss increased with increasing ambient air temperature, wind speed, solar load and hair density but decreased with increasing relative humidity, and evaporative heat loss increased with increasing ambient air temperature, wind speed, solar load and hair density, but
decreased with increasing relative humidity and thickness of the hair coat. A collaborative project (with USDA-ARS-MARC and HI) was conducted the summer of 2004 at the MARC at Clay Center, NE to determine the impact of genotype on heat tolerance of cattle to solar radiation. Four genotypes of 32 feedlot heifers were selected for different hair coat colors and different absorption rates to solar radiation. The four hair coat colors were black (Angus), white (Charolais), light tan (MARC I ) and reddish brown (MARC III). The heifers were assigned by genotype to one of two treatments: shade access and no-shade access. Body temperatures were monitored using vaginal temperature loggers and respiration rates were collected during midday as well as thermoregulatory behavior (lying in shade, lying in sun, standing in shade, standing in sun, feeding, and drinking). Meteorological measurements were taken throughout the experimental trial. The mechanistic model described above was used to do
thermal analysis. There was no significant difference between breeds for heifers in shade or sunlight at ambient temperature of 36C. Hair color played a significant role in solar radiation absorption. Cows with black and dark red colors absorbed high solar radiation than heifers with white and tan. The benefit of providing shade was apparent when ambient air temperature was 36C but was not as apparent when air temperature was 42C. Sensible heat load was sensitive to ambient air temperature, air velocity and density of hair coat.
Impacts
Heat stress in cattle decreases feed intake and growth, and in extreme cases, can cause death. Heat stress occurs when the weather patterns change suddenly and the temperature increases rapidly, or the temperature remains hot for several consecutive days with little or no recovery at night. A heat wave that occurred in Western Iowa in July 1995 caused an approximate loss of 3,750 head of cattle. Direct losses were estimated at 42.8 million and production losses at $28 million. The same heat wave also killed over 5,000 head of cattle in Northeast Nebraska. Various recognized methods that ameliorate heat stress, such as shades and sprinkler cooling, are not completely understood relative to their comparative effectiveness nor are the rates of return on system investments documented. This research is to investigate how different breed of heifers respond thermally and behaviorally in shade or in sunlight during a hot summer period.
Publications
- Jiang, M, K.G. Gebremedhin, and L.D. Albright. 2004. Numerical simulation of coupled heat and mass transfer through the hair coat. Presented at the Aug. 1-4, 2004 ASAE Annual International Meeting, Paper No. 044038, ASAE, 2950 Niles Rd,. St. Joseph, MI 49085-9659
- Hillman, P. E., C.N. Lee and S.T. Willard. P. 2005. Thermoregulatory responses associated with lying and standing in heat stressed dairy cows. Transactions of the ASAE (in press).
- Hillman, P.E. , K.G. Gebremedhin, T.M. Brown-Brandl, and C.N. Lee. 2005. Thermal analysis and behavioral activity of heifers in shade or sunlight. Seventh International Livestock Environment Symposium. May 18-20, 2005. Beijing, China (accepted).
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Progress 01/01/03 to 12/31/03
Outputs
To characterize air flow field in a ventilated space and heat exchange between cows and their microclimate, five different turbulence models were evaluated. Based on convergence and computational stability criteria, the RNG kappa-epsilon turbulence model was found to be the most appropriate model that characterizes the flow field in a ventilated space occupied by ten cows positioned at random. The total heat loss from the cows varied approximately between 215 and 710 W because of variations in flow fields surrounding the animals. In a second study, an eighteen day experimental trial was conducted this past August at the MS State U dairy farm to investigate behavioral and physiological responses of cows to heat stress in a freestall barn. Two groups of ten lactating cows per group were separated into two adjacent pens: one with freestall cooling and other without freestall spray cooling. The freestall cooling system detected the presence of a cow lying down individual
stalls using pressure transducers connected to air mattresses buried in the sand bedding. If a cow was present, about 130 ml of water was sprayed on the back of the cow every 5 minutes with minimal wetting of the bedding. Heat stress conditions at midday (THI: 78 to 85) occurred every day of the trail. Body temperatures of all 20 cows were measured continuously over the study period using vaginal temperature loggers. Milk production, somatic cell counts and bacteria in the milk were monitored. At midday (10 AM to 3 PM) timing of behaviors were observed for subsequent correlation to body temperature records. Cooling behaviors were separated from feeding behaviors by providing the freestall alley with water spray cooling distinct from the feed alley without water spray cooling. Data are presently being analyzed.
Impacts
In ventilated spaces of human, plant or animal facilities, characterization of the airflow filed is necessary in order to do energy budgets for animals, energy balances for plants, determine thermal comfort for humans, or to evaluate contaminate concentrations in ventilated rooms. With respect to our second study, it has been estimated by St-Pierre (Ohio State U, An. Sci.) that the US dairy industry losses up to nearly $900 million annually due to heat stress. By continuous monitoring of the body temperature matched with behavioral observations of cows we can better understand thermal behavior and physiology of dairy cows in commercial dairies during periods of heat stress. In doing so, these studies can provide management strategies to help reduce economic loss and to improve the well-being of cows exposed to heat stress.
Publications
- Gebremedhin, K.G. and B. Wu. 2003. Characterization of flow field in a ventilated space and simulation of heat exchange between cows and their environment. J. Thermal Biology 28(2003):301-319.
- Hillman, Peter, C.N. Lee and S. Willard. 2003. Thermal responses of dairy cows to heat stress with and without freestall cooling. Presented at the July 28-July 30, 2003, ASAE Annual International Meeting at Las Vegas, NV. Paper No. 034036, ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA
- Hillman, Peter, S. Willard, C.N. Lee and S.D. Kennedy. 2003. Efficacy of a vaginal temperature logger to record body temperatures of dairy cows. Presented at the July 28-July 30, 2003, ASAE Annual International Meeting at Las Vegas, NV. Paper No. 034011, ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA
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Progress 01/01/02 to 12/31/02
Outputs
Three studies were conducted this past year. In the first study, the effectiveness of a new freestall spray system for cooling heat-stressed dairy cows was tested for 5 days during August at the MS State U dairy farm. Two groups of ten lactating cows per group were separated into two adjacent pens: one with freestall cooling and other without freestall cooling. The cooling system detects the presence of a cow lying down individual stalls using an ultrasonic detector. If a cow is present, about 180 ml of water is sprayed on the back of the cow every 3 minutes with minimal wetting of the bedding. Heat stress conditions (midday THI: 81 to 84) occurred every day of the 5 day trail. At midday body temperature, respiration rate, dorsal surface temperatures and time spent lying down or standing were measured. Milk production and somatic cell counts were also recorded. Preliminary data analyses indicate that cows were cooled by spray while lying in stalls. Cows exposed to
freestall spray had a lower rate of body temperature rise (0.3 C/hr compared to 0.6 C/hr), a lower respiration rate (71 breaths/min compared to 91 breaths/min) and a lower dorsal skin temperatures (34 C compared to 36 C) than cows with no freestall spray. In the second study, a vaginal temperature logger device was designed and tested for measuring body temperature. A temperature logger was encased in a specially constructed, soft plastic anchor with 8 fingerlike projections to keep the logger from being discharged. The vaginal temperature loggers were within 0.5 C of the spot rectal temperature measurements. In the third study, the rate of evaporation from the skin of black and white Holstein cows, exposed to simulated sunlight at a new environmental chamber at the U of AZ, was measured using our unique portable calorimeter. Data are being analyzed to determine the impact of hair coat color on solar load.
Impacts
It has been estimated by St-Pierre (Ohio State U, An. Sci.) that the US dairy industry losses up to nearly $900 million annually due to heat stress. Our studies are designed to help reduce this loss and to improve the well-being of the cows. Our spray system is designed to provide effective cooling in freestalls, without wetting the bedding, so that cows will lie in stalls longer, without the need to stand to keep cool. Standing and walking is thought to decrease milk production and the well-being of cows. The vaginal temperature loggers provide a powerful research tool for observing the thermal response of cows under different housing conditions by providing a continuous and accurate record of body temperature at low cost. Finally, a better understanding of the impact of direct sunlight on thermal energetics of cows and the benefits of lighter hair coat, shade and wetting are needed to optimize dairy management during times of severe heat stress, especially when many
dairymen feed cows under direct sunlight.
Publications
- Hillman, P.E. and C.N. Lee. 2002. Field test of a new cooling system for dairy cows in a freestall facility. Presented at the July 28-July 31, 2002 ASAE Annual International Meeting/CIGR XVth World Congress. Paper No. 024065, ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA.
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Progress 01/01/01 to 12/31/01
Outputs
The first field trial of a new cooling system for cows in freestalls was conducted during August 2001 at a commercial dairy farm near Bakersfield, California. The system detects the presence of a cow lying down in an individual freestall using an ultrasonic detector. When a cow is present, about 130 ml of water is sprayed on the back of the cow every 3 minutes. This is sufficient water to keep the skin wet with minimum runoff. Ten stalls equipped with the new system were accessible to ten randomly selected lactating Holsteins for five consecutive days between noon and 3:00 PM. During this experimental period, the amount of time cows spent lying down in stalls under the new system was compared to time cows spent lying down at 20 stalls without the new cooling system. All cows had access to feed alley spray and were cooled with fans. Respiration rates and dorsal surface temperatures were also recorded as a measure of thermal response with minimal behavioral disruption.
Air temperatures, relative humidity, and airflows were also recorded. Preliminary data analyses include the following observations. THI ranged from 77 to 83 during the experimental observations. Cows with water spray spent about 62% more time lying down in stalls than cows without water spray (65 minutes compared to 40 minutes). Water spray reduced respiration rates by 39% percent (80 breaths/min without spray, 49 breaths/min with spray). Water spray also depressed dorsal surface temperature by about 2.2C (33.8C without water spray, 31.6C with water spray).
Impacts
During periods of hot weather, many dairy farmers cool cows with fans and water spray in feed alleys and holding pens. Dairymen avoid spraying cows in freestalls because the resulting wet bedding may cause mastitis. Unfortunately, cows are not cooled adequately in freestalls with fans alone and therefore they stand up and walk to feed alleys to stand under sprayers. Constant standing or movement decreases milk production. Developing a water spray system that provides effective cooling without wetting the bedding would solve this problem.
Publications
- Hillman, P.E., K.G. Gebremedhin, A. Parkhurst, J. Fuquay, and S. Willard. 2001. Evaporative and convective cooling of cows in a hot and humid environment. Livestock Environment VI. Proceedings of the Sixth International Symposium. Galt House Hotel, Louisville, KY. May 21-23, 2001. ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA.
- Hillman, P.E., C.N. Lee, J.R. Carpenter, K.S. Baek, and A. Parkhurst. 2001. Impact of hair color on thermoregulation of dairy cows to direct sunlight. Presented at the July 29-August 1, 2001 ASAE 94th Annual International Meeting, Paper No. 014031, ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA.
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Progress 01/01/00 to 12/31/00
Outputs
Two projects were conducted this past summer to investigate the responses of dairy cows to heat stress. In both studies, we utilized our unique portable calorimeter to determine evaporative and convective heat losses. In the first project we investigated the evaporative and convective heat losses from the surface of heat-stressed, lactating Holstein cows exposed to wetting and fan cooling in a hot, humid environment in Mississippi. These cows were cooled by wetting their dorsal surface or by blowing air over them or by a combination of both. When wetted, the temperature of the dorsal skin surface dropped 4 C and respiration rate dropped 16 breaths/min. The rectal temperatures of cows wetted at 20 min intervals with air blown over them at 2.2 m/s dropped 0.5 C/hr. Wetting alone lowered body temperature more than only blowing air over them. Evaporative heat loss accounts for more than 82% of the total heat loss from the wetted skin. In the second project we studied the
effect of hair coat color on the responses of heat-stressed cows exposed to 1.5 hr of direct sunlight in Hawaii. Three white and three black lactating Holstein cows were compared. Cows with white hair coat absorb about 64% of the short wave radiation, while cows with black hair coat absorb about 89% of the short-wave radiation. Direct sunlight increased the surface temperature of the black cows by 5.3 C and the white cows by 1.1 C. Rectal temperatures of black cows increased 0.9 C/hr, while white cows increased 0.5 C/hr. Respiration rates for both white and black cows increased about 20% with no apparent difference between them. Calorimeter data are presently being analyzed.
Impacts
This study develops strategies and practices to alleviate heat-stress in dairy cows. The problems are national in character. Dairies can loose 10 to 15% in milk production during periods of heat stress, which is equivalent to a loss of $1 per cow per day. For example, a 2000 cow dairy operation in CA may incur a $120,000 loss in milk production for 60 days of hot weather. In addition, heat stress lowers conception rate and thus delays when a cow can go back into production. Heat-stressed cows will slug feed at night, resulting in ruminal acidosis, a cause of lameness. Treatment of lameness can cost $300 per cow. Cow comfort and well-being are severely compromised during heat-stress.
Publications
- Wu, B. and K.G. Gebremedhin. 2001. Numerical simulation of flow field around a cow using a 3-D body-fitted coordinate system. Presented at the July 9-12, 2000 ASAE Annual International Meeting, Paper No. 004115, ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA.
- Hillman, P.E. and D.V. Armstrong. 2000. Cool cows, not barns. Direct wetting and blowing with fans help return heat-stressed cows to normal. Hoard's Dairyman. 145(10):380.
- Hillman, P.E., K.G. Gebremedhin, D. Aneshansley, and A. Landers. 2000. Design of a new cooling system for dairy cows in freestall facilities. Presented at the July 9-12, 2000 ASAE Annual International Meeting, Paper No. 004110, ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA.
- Gebremedhin, K.G. and B. Wu. 2001. A model of evaporative cooling of wet skin surface and fur layer. Presented at the July 9-12, 2000 ASAE Annual International Meeting, Paper No. 004114, ASAE, 2950 Niles Rd., St. Joseph, MI 49085-9659, USA.
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Progress 01/01/99 to 12/31/99
Outputs
An experiment was conducted to measure the effectiveness and interaction of two methods used to cool cows: (1) forced convection over the cows dorsal surface using fans and (2) wetting the dorsal surface of the cows with low pressure misting. Three lactating Holsteins cows of similar body weight and milk production were used during early July of 1999 at the University of Arizona Research Dairy Farm. Three levels of forced convection were implemented: (a) fan off, (b) fan producing 0.9 m/s, and (c) fan producing 2.3 m/s. Three levels of wetting were considered: (a) DRY - no wetting, (b) LOW - moderate wetting (saturate dorsal hair coat every 20 min), and (c) MAX - maximum wetting (saturate dorsal hair coat every 10 min). For each treatment, convective, radiant, and evaporative heat losses were measured from the hair coat surface using a portable calorimeter. This apparatus underwent extensive revision this past year to improve its accuracy and versatility. The
revisions included faster response time for calibration and measurement and to include the ability to adjust to animals of different hair coat thickness. Wetting the hair coat and blowing air over the cows were both effective in cooling cows, although only wetting the hair is more effective than only blowing air over the cow. Maximum wetting of the cows alone lowered core temperature by about 0.7 to 0.8 C. Blowing air over the cows at 2.3 m/s alone lowered core temperature by about 0.4 to 0.6 C. The effect of combining both forced air over the cows and wetting are additive. Drier air from the surrounding environment when blown over the moistened hair coat increases evaporative cooling. Maximum cooling through wetting and forced air lowered core temperature by about 1.3 C. The portable calorimeter yielded reasonable estimates of the computed rate of core temperature change to measured rate of core temperature change.
Impacts
(N/A)
Publications
- Hillman, Peter and Kifle Gebremedhin. 1999. A portable calorimeter to measure heat transfer in livestock. Presented at the July 18-21, 1999 ASAE Annual International Meeting, Paper No. 994212, ASAE, 2950 Niles Rd,. St. Joseph, MI 49085-9659, USA.
- Armstrong, D.V., P.E. Hillman, M.J. Meyer, J.F. Smith, S.R. Stokes and J.P. Harner III. 1999. Heat stress management in freestall barns in the western U.S. Proceedings of the 4th Western Dairy Management Conference. April 8-10, 1999. Las Vegas, Nevada, pp. 87-98.
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Progress 01/01/98 to 12/31/98
Outputs
Energy exchange of beef cattle in thermoneutral and hot environments was measured in early August 1998 at the University of Missouri Brody Environmental Laboratory. The portable calorimeter, designed and constructed by us, was utilized to measure evaporative heat loss, convective heat exchange, and radiant heat exchange from the hair coat surface of four Simmental heifers at 20, 24, 30, and 32 C ambient temperatures and 0.1 and 1.1 m/s air velocities. Utilizing the portable calorimeter allowed us to understand the complex interaction between the environment and beef cattle in their natural habitat. Measurement of heat exchange is the first step towards calculating energy budget of an animal. Data from this study is presently being analyzed. The portable calorimeter was rebuilt in June 1998 in order to be able to vary air velocity across the hair coat during calorimetric measurements. Field testing of the calorimeter at the Brody Laboratory suggested the need for
further refinement of the system. Presently, the penultimate version of the calorimeter is being constructed. Design objectives include faster response time for calibration and measurements and to have the ability to adjust the system to different hair coat thickness. In collaboration with the University of Arizona and Kansas State University, heat stress management of 24 free-stall dairy farms were investigated in California and Texas. Respiration rates were measured as an indicator of heat stress. Air temperature, relative humidity, air flow, and amount of water spray, to enhance evaporative heat loss, were monitored. Temperature-humidity index (THI) alone show no correlation on respiration rate. Providing forced air cooling without water spray or water spray without forced air cooling showed very little reduction in heat stress, but was effective when forced air cooling and water spray were combined.
Impacts
(N/A)
Publications
- Armstrong, D.V. and P.E. Hillman. 1998. Response to cooling does vary between breeds. The Western Dairyman 79(4):24-33.
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Progress 01/01/97 to 12/31/97
Outputs
The portable calorimeter utilized during July 1996 to measured heat loss/gain of lactating cows in hot, semi-arid environments was improved and was used again to measure heat loss/gain of Holsteins, Brown Swiss, and Jersey cows during July 1997 in Tucson and Phoenix, Arizona. Heat loss/gain measurements were taken on cows (1) under shade without evaporative cooling, (2) under shade with fans and low pressure misting, (3) under shade with an orchard fan and misting, and (4) under shade with high-velocity fans and high-pressure fogging. For all three breeds the fourth system was the most effective cooling system because the cows had the lowest respiration rates and the highest milk production under this system. This system facilitates cutaneous evaporation, the major avenue of heat loss for all three breeds, by wetting the hair coat and replacing the moist air above hair coat with drier surrounding air more effectively than the other systems. Brown Swiss expressed
higher rates of cutaneous evaporation per unit area than Holsteins or Jerseys. Jerseys had the lowest rate of the three breeds. This ranking was true for all four cooling systems where comparisons were made.On an analytical front, a model that predicts the temperature profile and heat flux through irradiated hair coat was developed. The method incorporates thermophysical and optical (individual and bulk) properties of the hair coat. Temperature within the hair coat was higher than at the skin surface resulting in a heat gain at t.
Impacts
(N/A)
Publications
- Gebremedhin K.G, H. Ni, and P.E. Hillman. 1997. Modeling temperature profile and heat flux through irradiated fur layer. Transactions of ASAE, Vol. 40(5):1441-1447.
- Armstrong, D.V. and P.E. Hillman. 1998. Evaluation of Brown Swiss, Holstein and Jersey under hot arid climates for dairy production. Western Dairyman Magazine (in press).
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Progress 01/01/96 to 12/30/96
Outputs
A battery powered, portable calorimeter was designed and constructed to measure heat exchange at the hair coat of cattle outdoors. The apparatus is placed tight against a cow to measure heat fluxes from a fixed area of the hair coat. During July 1996, the portable calorimeter was tested at the University of Arizona Experimental Diary farm in Tucson. Heat loss/gain measurements from cows under (1) under sunlight, (2) under shade without evaporative cooling, (3) under shade with fans and low pressure misting, and (4) under shade with high-velocity fans and high-pressure fogging, were conducted. Cows are under considerable heat stress while under direct sunlight, and shade without misting was not cool enough to alleviate the problems of heat stress. Mist coupled with shade helped alleviate heat stress. It was more effective when high-velocity fans and high-pressure fogging was used. This cooled the air and the roof. Data gathered by the portable calorimeter revealed that
expensive air movement systems may not be more effective than constructing a passive misting system encircling the shaded enclosures.
Impacts
(N/A)
Publications
- Hillman, P. E., K.G. Gebremedhin and Donald E. Johnson. 1996. Effect of heat loss to cold clear skies on daily weight gains of cattle in winter feedlots. Presented at the July 14-18, 1996 ASAE Annual International Meeting, Paper No. 96412
- Hillman, P.E. and K.G. Gebremedhin. 1997. A portable calorimeter to measure heattransfer from cattle hair coats. Proceedings of the Fifth International Livestock Environment Symposium. Bloomington, MN May 29-31, 1997. (in press)
- Gebremedhin, K.G., H. Ni and P.E. Hillman. 1997. Impact of solar radiation on energy balance of animals with hair coat. Proceedings of the Fifth International Livestock Environment Symposium. Bloomington, MN May 29-31, 1997. (in press).
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Progress 01/01/95 to 12/30/95
Outputs
Cattle in commercial feedlots in northern Colorado have 12% lower daily gain than summer fed cattle but do not differ appreciably in feed intake. Only about half of this difference can be explained from variation in growth rate and the effects of environmental variables of temperature and wind. Cold clear winter night skies might cause additional heat loss via long-wave radiation that the energy budget models fail to take into account. Pelt samples from winter cattle from the Colorado Experiment Station were placed in a convective calorimeter where radiant and convective heat losses were measured: ambient temperature was 14.7 C, air velocity was 1.7 meters/sec and the relative humidity was 65%. The samples were placed on a guarded heat plate where the temperature beneath the skin was held at 36 C. The overall heat transfer coefficient for winter pelts with lofts greater than 4 mm was constant (9.8 +/- 2.0 watts per square meter per degree C). Using this heat transfer
coefficient, heat loss to a clear cold night sky temperature (-28 C) or to a cloudy night sky temperature (same as air temperature or -3 C) was computed. The difference in heat loss between a clear sky and a cloudy sky is about 80 W (1000 kcal/day) for a 400 kg animal with about 4.3 square meters of surface area of which less than 50% faces the sky. One-thousand kcal/day is enough energy to produce about 0.3 kg of weight gain.
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Progress 01/01/94 to 12/30/94
Outputs
To test the efficacy of cooling heat-stressed cattle by spraying them with waterand/or by increasing air flow over them with fans, we designed and tested a unique apparatus to measure evaporative, radiative, and convective heat loss through fur. The apparatus is a modified guarded hot plate placed inside our existing forced convection calorimeter. Fur samples were placed on top the plate where a known amount of heat passes through the fur sample and into the calorimeter. An adiabatic arrangement below the flat heater insures that all the heat from the flat heater passes through the fur sample. The total sum of the independent measures of evaporative, radiant, and convective heat loss was within 15% of the measured energy input to the plate heater. Five fur samples of summer cattle from Colorado were used to test the cooling effect of wetting or wind or both. Increasing air flow from 0.5 to 1.7 m/s over the dry fur increased heat loss by only 15%, primarily due to an
increase in convective heat loss. Wetting the fur at 0.5 m/s increased total heat loss by about 110%, due to a dramatic increase in evaporative heat loss from 100 to 400 watts per square meter. Convective heat loss and radiant heat loss showed little change. Increasing air flow to 1.7 m/s over the wetted skin increased total heat loss another 25% from additional evaporation. These results suggest that wetting the fur alone, without the use of fans, should produce the desired cooling effect to reduce heat stress.
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Progress 01/01/93 to 12/30/93
Outputs
During the past year we measured heat loss through pelt samples of winter and summer cattle from the Colorado Experiment Station. The insulation characteristics of the fur between winter and summer cattle may help explain why winter cattle have 12% lower weight gain than summer cattle even though summer and winter cattle have the same feed intake. Present environmental models do not account for the differences. These models do not fully account for radiant heat loss to a cold clear sky, which might explain part of the observed discrepancy. Convective, radiant, and evaporative heat losses of nineteen pelt samples were measured using our improved forced-convection calorimeter. Thicker pelts had greater insulation, i.e., thermal conductance (watts per square meter per degree C) based on total heat loss (conduction, convection, radiation, and evaporation from the fur surface) was inversely correlated to pelt loft. Winter loin and belly samples were thicker and had lower
conductance than summer samples. However, the average pelt loft between summer and winter shoulder and rump samples were not different and no differences in heat loss between them were observed. Inasmuch as the shoulder and rump areas of the winter cattle that face the sky were not better insulated than the summer cattle may contribute to a higher heat loss to cold, clear winter skies than was previously accounted for in thermal models.
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Progress 01/01/92 to 12/30/92
Outputs
A novel partitional calorimetry that permits measurements and partition of heat flux densities, such as convection, radiation and evaporation through animal hair coat (fur) was developed and constructed. Sensible and latent heat losses from a cow was simulated using a cylinder covered with real cow pelt under different air temperatures, air velocities and degree of fur wettedness. Equations that determine heat transfer coefficients for convection, radiation and evaporation through animal hair coat were developed. A method is being developed to correlate the transfer coefficients with air temperature and wind penetration into the hair coat.enetration into the hair coat.
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Progress 01/01/90 to 12/30/90
Outputs
Following measurements made last year on the convective and radiant heat loss through dry and wet Holstein calf fur samples, several changes and enhancements in the newly constructed forced-convection calorimeter were indicated. Two relative humidity settings are now possible: two separate, temperature controlled baths with air bubbling through them allows immediate access to two different dew point settings. Numerous changes were made to the system for stability and accuracy of the dew point, air velocity, and air temperature within the calorimeter. These changes were followed with a comprehensive calibration of convective, radiant, and evaporative systems. In addition to these changes in the calorimeter itself, two additional enhancements are being incorporated: solar insulation of the furred skin and the transfer of water vapor through the fur layer. A solar simulator has been recently acquired, which utilizes a 1000 watt Xenon lamp. This lamp is one of the best, if
not the best, simulator of sunlight with respect frequency and intensity in the ultraviolet, visible, and the near-infrared. Furred samples will also be wrapped around a wet, porous surface to mimic the evaporation through the skin and fur. Both solar insulation and evaporation can be studied in a simulated windy environment. In doing so, questions of energy budgets of cattle housed outside during periods of both cold stress and heat stress can be modelled, providing important information for the design of shelters.
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Progress 01/01/89 to 12/30/89
Outputs
A forced-convection calorimeter which allows measurement of convective, radiant & latent heat loss was constructed & tested. The chamber allows measurement of low levels of heat losses through a range of air velocities from .4-1.6m/s & air temperatures from 10-40C. When a Holstein calf fur sample was wetted, heat loss through it increased by 10-15% at 12.5C air temperature. Although latent heat loss increases with wet fur, less heat is lost through convection & radiation because evaporation cools the fur surface. As long as wind conditions are nottoo severe, calves are able to maintain insulation qualities of their fur when it rains in their natural environment. Of the 3 avenues of heat loss, convection accounts for most of the increase when air velocities are raised from .4-1.6m/s. An ammonia/humidity controller for a calf nursery was tested & performed as designed. Ammonia levels were not allowed to exceed about 13 ppm for more than a few min. Except when it was
warm & rainy did the relative humidity in the nursery exceed the set-point of 70%. When it did exceed this set-point, fresh air ventilation was at its maximum, preventing any buildup of ammonia. The ventilation system in this heated nursery provides just enough fresh air to keep ammonia & relative humidity at safe levels so as to conserve energy during cold weather. For the past 3 yrs of operation, not 1 calf has been lost due to pneumonia & the incidence of the respiratory disease has been as low as calves raised in outside hutches.
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Progress 01/01/88 to 12/30/88
Outputs
An analytical model which perdicts airflow from pressurized perforated double polyethylene tubes used for air distribution in calf nurseries was developed. Past designs of these systems have been purely by trial-and-error or experience. The system consisted of two concentric tubes. The inner tube was tapered while the outer one had a constant diameter. An optimization scheme for the hole schedule was developed, and sensitivity analysis for the taper of the inner tube was performed. The model predicted a uniform air distribution throughout the length of the tube. Knowing the airflow characteristics of perforated ducts would allow designers to match the performances of ducts with that of fans, and thus select fans with adequate airflow and minimal required horsepower. Two systems of offering milk to 72 calves was studied viz. 8% of birthweight for 3 weeks and 10% from 4 to 6 weeks or the reverse. Neither growth nor starter intake was different between treatments. The
final data from the report tendered in 1987 suggest that within the wide ranges of neonatal nutrition and the limitations of the methods used to assess the immune response, the calf's immune system was not materially affected. It suggests that the calf's ability to mount an immune reaction is not affected by rather significant ranges of nutritional insults. Methods of feeding did not affect measurements.
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Progress 01/01/87 to 12/30/87
Outputs
The ventilation system of two extant environmentally controlled, 20 calf nurseries has been under study to perfect a unit which provides adquate air quality with a minimum of manual attention by the barn staff. Use of an ammonia sensor alone was not adequate to provide adequate air quality. Adding a relative humidity sensor permitted good control of about 75% relative humidity. Manual intervention can intercede when ambient air is cold and has a very high relative humidity (spring and fall rains). A total of 114 Holstein neonatal calves were reared on three levels of liquid feeding (high-medium-low) to 7 weeks. Within each group one-half were weaned gradually (1/2 liquid feed during the last week of milk feeding) and one half were weaned abruptly. Rate of gain was superior for the high group, a tendency which persisted until twelve weeks. No differences in growth occurred between abrupt or gradual weaning. There was a greater immune response to injected chick red blood
cells at 12 weeks of age fed higher levels of milk and weaned gradually. Response to an intradermal injection of a phytohemagglutinin was greater at 12 weeks for calves weaned gradually. An ACTH challenge resulted in higher cortisol levels for calves fed lower levels of milk suggesting a more moderate level of stress in those calves. Calves reared in environmentally controlled nurseries in the winter season grew as well as calves housed in hutches during the milk weather.
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Progress 01/01/86 to 12/30/86
Outputs
A calf nursery ventilation system employing a central polytube was established last year. Utilization of a dual polytube (one inside the other) provided a more even distribution of air than one alone. Plastic curtains looped above the two rows of calves, hastened the removal of aerosol particles towards the collecting ducts at the rear of the calves. An ammonia sensor has been installed to aid in air quality control. Dairy replacement heifers were reared on two milk schedules (1) 10% of birthweight from 0-3 wk of age and 8% of birthweight from 3-6 wk of age; (2) 8% of birthweight from 0-3 wk of age and 10% of birthweight from 3-6 wk of age. Growth and starter consumption was superior on treatment (1). A much reduced liquid intake utilizing a milk replacer pellet has been shown to be satisfactory for adequate neonatal performance.
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Progress 01/01/85 to 12/30/85
Outputs
A ventilation system has been installed to provide filtration of aerosols, uniform air distribution and precise control of air changes. All air entering the nursery passes through a 95% DOP filter to remove particles as small as 0.5 microns and distributed from a central polyethylene duct. Both recirculated air and exhaust air are drawn from the nursery via rigid collection ducts running parallel to the incoming duct. The introduction of fresh air is modulated by louvers through a proportioning motor and thermostat. There is a minimum setting for fresh air but it can be adjusted as calves are added or removed from the nursery. Environmental data can be recorded by computer.
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