title: Production and physiological responses of heat-stressed lactating dairy cattle to conductive cooling.
abstract: The objective of this research was to test the effectiveness of conductive cooling in alleviating heat stress of lactating dairy cows. A conductive cooling system was built with waterbeds (Dual Chamber Cow Waterbeds, Advanced Comfort Technology Inc., Reedsburg, WI) modified to circulate chilled water. The experiment lasted 7 wk. Eight first-lactation Holstein cows producing 34.4±3.7kg/d of milk at 166±28 d in milk were used in the study. Milk yield, dry matter intake (DMI), and rectal temperature were recorded twice daily, and respiration rate was recorded 5 times per day. During wk 1, the cows were not exposed to experimental heat stress or conductive cooling. For the remaining 6 wk, the cows were exposed to heat stress from 0900 to 1700h each day. During these 6 wk, 4 of the 8 cows were cooled with conductive cooling (experimental cows), and the other 4 were not cooled (control cows). The study consisted of 2 thermal environment exposures (temperature-humidity index mean ± standard deviation of 80.7±0.9 and 79.0±1.0) and 2 cooling water temperatures (circulating water through the water mattresses at temperatures of 4.5°C and 10°C). Thus, a total of 4 conductive cooling treatments were tested, with each treatment lasting 1 wk. During wk 6, the experimental and control cows were switched and the temperature-humidity index of 79.0±1.0 with 4.5°C cooling water treatment was repeated. During wk 7, waterbeds were placed directly on concrete stalls without actively cooling the water. Least squares means and P-values for the different treatments were calculated with multivariate mixed models. Conductively cooling the cows with 4.5°C water decreased rectal temperature by 1.0°C, decreased respiration rate by 18 breaths/min, increased milk yield by 5%, and increased DMI by 14% compared with the controls. When the results from the 2 cooling water temperatures (4.5°C and 10°C circulating water) were compared, we found that the rectal temperature from 4.5°C cooling water was 0.3°C lower than the rectal temperature with 10°C cooling water, but the other measurements (respiration rate, milk production, and DMI) did not show a statistically significant difference between the cooling water temperatures. Placing waterbeds on concrete stalls without additional cooling did not have a measurable effect in alleviating the heat stress of the cows.
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853. Electronic address: kmp263@cornell.edu.
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Perano
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Usack
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853.
authors.forename: Largus T
authors.initials: LT
authors.lastname: Angenent
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853.
authors.forename: Kifle G
authors.initials: KG
authors.lastname: Gebremedhin
mesh_terms: D000818:Animals; D001512:Bedding and Linens / Q000662:veterinary*; D001831:Body Temperature; D002417:Cattle; D002418:Cattle Diseases / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D003612:Dairying / Q000379:methods*; D005260:Female; D018882:Heat Stress Disorders / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control / Q000662:veterinary*; D007774:Lactation; D011897:Random Allocation
keywords: conductive cooling; heat stress; physiological response; production response; waterbed