Universidad Autónoma de Baja California, Instituto de Ciencias Agrícolas, 21705, Valle de Mexicali, Baja California, México.
Facultad de Medicina Veterinaria y Zootecnia, Universidad de Colima, 28930 Tecomán, Colima, México.
Int J Biometeorol. 2021 Aug;65(8):1443-1450. doi: 10.1007/s00484-021-02115-y. Epub 2021 Mar 19.
Impacts of an additional cooling event during the night on physiological and productive parameters of two breeds (B) of dairy cows under severe heat stress conditions were determined. Fifteen Holstein (H) and 15 Jersey x Holstein (JxH) cows were assigned to one of the two cooling strategies (CS), where the difference was an added 1 h cooling event during the night (i.e., 3X and 4X cooling events) with the 4X group having the added night cooling event. Maximum and minimum average temperature/humidity indices during the study were 86 and 77 units, respectively. There were no CS x B interactions for any response variable. Body condition score (BCS) was similar between CS, but H cows had higher (P<0.05) condition than JxH. There were no differences in rectal temperature due to CS or B. Respiration rate between breeds and cooling strategies were similar throughout the day. However body surface temperatures of head, thurl, right flank, and udder were higher (P<0.05) in 3X versus 4X cows, and H cows maintained a higher (P < 0.05) temperature in thurl and right flank than JxH during PM hours. Metabolites and hormone concentrations were not affected by CS, but H cows had lower (P < 0.05) triiodothyronine and higher (P < 0.05) thyroxine, than JxH. The 4X cows had higher (P<0.05) milk yield and milk energy output than 3X cows. While H cows produced more milk than JxH, the latter had higher (P < 0.05) milk component levels. In general, JxH cows were judged to have to demonstrate a more desirable physiological response and milk composition outcome than H cows. An additional night cooling event was judged to result in more desirable physiological and productive responses than in cows without this extra night cooling event under the extremely hot and dry environmental conditions during the study.
研究了在严重热应激条件下，夜间额外冷却事件对两种奶牛（B）生理和生产参数的影响。将 15 头荷斯坦（H）和 15 头泽西牛 x 荷斯坦（JxH）奶牛分配到两种冷却策略（CS）之一，差异在于夜间增加了 1 小时的冷却事件（即 3X 和 4X 冷却事件），4X 组有夜间冷却事件。研究期间，最大和最小平均温度/湿度指数分别为 86 和 77 个单位。对于任何响应变量，CS 和 B 之间没有交互作用。CS 之间的体况评分（BCS）相似，但 H 奶牛的体况比 JxH 奶牛好（P<0.05）。由于 CS 或 B，直肠温度没有差异。全天品种和冷却策略的呼吸率相似。然而，头部、胸部、右侧肋部和乳房的体表温度在 3X 牛中高于 4X 牛（P<0.05），在下午和晚上，H 奶牛的胸壁和右侧肋部温度高于 JxH 奶牛（P<0.05）。代谢物和激素浓度不受 CS 影响，但 H 奶牛的三碘甲状腺原氨酸水平较低（P<0.05），甲状腺素水平较高（P<0.05），而 JxH 奶牛的三碘甲状腺原氨酸水平较低（P<0.05），甲状腺素水平较高（P<0.05）。4X 奶牛的产奶量和产奶能量输出高于 3X 奶牛。虽然 H 奶牛的产奶量高于 JxH 奶牛，但后者的牛奶成分水平较高（P<0.05）。总的来说，与 H 奶牛相比，JxH 奶牛表现出更理想的生理反应和牛奶成分结果。在研究期间极其炎热和干燥的环境条件下，与没有额外夜间冷却事件的奶牛相比，夜间额外冷却事件被认为会产生更理想的生理和生产反应。
