Innovative cooling strategies: Dairy cow responses and water and energy use

摘要

Producers in the western United States commonlyuse spray water at the feed bunk and fans in the lyingarea to mitigate heat stress in dairy cows. Often,spray water cycles on and off with fans turning onwhen a preset air temperature is reached. Althoughthis method can be effective, innovative strategies areneeded to reduce water and energy use. We evaluatedthe effectiveness and resource efficiency of 4 coolingtreatments on behavioral and physiological responsesin dairy cows housed in a freestall barn: (1) conductivecooling in which mats with recirculating evaporativelycooled water were buried under sand bedding (Mat;activated at 18.9°C); (2) targeted convective coolingin which evaporatively cooled air was directed towardthe cows through fabric ducts with nozzles at both thefeed bunk and lying areas (Targeted Air; activated at22°C); (3) evaporative cooling, with spray water in thefeed area and fan over the freestalls (Baseline; activatedat 22°C); and (4) evaporative cooling with half theamount of spray water used in the Baseline and the fanmoved to the feed bunk (Optimized Baseline; activatedat 22°C). In a crossover design, 8 groups of cows (4/group) producing an average (± standard deviation) of37.5 ± 4.5 kg/d of milk were tested for 3 d per treatment.For ethical reasons, beginning at 30°C, the Mattreatment was supplemented with Baseline cooling andthe Targeted Air treatment had spray water at the OptimizedBaseline rate. We recorded body temperature,posture, and location within the pen every 3 min for24 h/d, and respiration rates every 30 min daily from1000 to 1900 h. Daily air temperature averaged (±SD)26.3 ± 7.1°C during 24 h and 33.3 ± 4°C from 1000 to1900 h. We used pairwise comparisons of each treatmentto Baseline to evaluate response variables. Milkproduction did not differ across treatments, nor didtime spent lying (51 ± 2%/d on average). Respirationrates did not differ across treatments overall (61 ± 3breaths/min), but on an hourly basis, cows in the Mattreatment had a significantly higher rate than those inBaseline, at h 10 and 11 (70 vs. 58–59 breaths/min).Body temperature averaged 38.7 ± 0.05°C across treatmentsand was 0.2 to 0.3°C higher in the Mat treatmentthan in Baseline at h 10, 11, 20, 21, and 22. Theseresults collectively indicate that the Mat treatment didnot effectively reduce indicators of heat load comparedwith Baseline. In contrast, Targeted Air and OptimizedBaseline were both effective but differed in aspects ofefficiency. Targeted Air used the least amount of waterbut the most energy of all options tested. In conclusion,more efficient heat abatement options were identified,particularly an Optimized Baseline strategy, which cutwater use in half, required the same amount of energyas the Baseline, and maintained similar physiologicaland behavioral responses in cows.