Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32610, USA.
Dairy Design Engineers, Gainesville, FL, 32608, USA.
Int J Biometeorol. 2022 Nov;66(11):2169-2181. doi: 10.1007/s00484-022-02358-3. Epub 2022 Sep 26.
Heat stress abatement strategies for pre-weaned dairy calves are seldom evaluated. An experiment was conducted to evaluate the effects of housing calves under a barn and provision of fans to calves housed under a barn on calfhood performance. The experiment was conducted in a dairy in southern Georgia, USA. Male Holstein calves (n = 60; 0 to 68 day of age) were assigned randomly at birth (day 0) to 1 of 3 treatments: hutch outdoors with 50% of its area covered with plywood (control = 20), hutch in a barn with no cooling (SH = 21), and hutch in a barn with ceiling fans (SHF = 19). Body weight (BW) was measured at birth, and total serum protein and wither-height were measured 24 to 48 h after birth. A sub-set of hutches was evaluated for air speed and temperature, and rectal temperature (RT) and respiratory frequency (RF) of calves housed in these hutches were measured at 0900 and 1500 h. Intakes of liquid feed (days 14 to 63) and starter (days 14 to 68) were recorded daily, BW and wither-height were measured weekly, and feed efficiency was calculated weekly. Blood was sampled on days 1, 14, 28, 42, 49, 52, 56, 58, 63, and 65 for the measurement of fatty acids, β-hydroxybutyrate, glucose, and insulin. The SHF treatment resulted in air velocity 0.56 to 0.83 m/s greater (P < 0.01) than the control and SH treatments, respectively, whereas the control treatment resulted in air temperature 1.2 to 3.2 °C greater (P < 0.01) than the SH and SHF treatments, respectively. The RT of calves in the control treatment was 0.1 to 1.1 °C greater (P ≤ 0.03) than the SH and SHF treatments, respectively, and the control treatment resulted in RF 39.4 to 60.2 mov/min greater (P < 0.01) than the SH and SHF treatments, respectively. Treatment did not (P ≥ 0.27) affect feed efficiency and concentrations of metabolites and insulin, but calves in the control treatment were 2.6 cm shorter (P = 0.03) than calves in the SHF treatments at weaning. Provision of fans to calves housed under a barn reduced RT, RF, but only had a minute impact on wither-height.
对断奶前奶牛犊牛的热应激缓解策略很少进行评估。进行了一项实验，以评估在牛舍中饲养犊牛和在牛舍中为犊牛提供风扇对犊牛期表现的影响。该实验在美国佐治亚州南部的一个奶牛场进行。雄性荷斯坦犊牛（n=60；0 至 68 日龄）在出生时（第 0 天）随机分配到 3 种处理之一：带有 50%覆盖胶合板的室外小屋（对照=20）、无冷却设施的牛舍中的小屋（SH=21）和带有天花板风扇的牛舍中的小屋（SHF=19）。在出生时测量体重（BW），在出生后 24 至 48 小时测量总血清蛋白和肩高。对一小部分小屋进行了空气速度和温度评估，并在 0900 和 1500 小时测量了这些小屋中犊牛的直肠温度（RT）和呼吸频率（RF）。记录了 14 至 63 天的液体饲料和 14 至 68 天的起始饲料的摄入量，每周测量 BW 和肩高，每周计算饲料效率。在第 1、14、28、42、49、52、56、58、63 和 65 天采集血液样本，以测量脂肪酸、β-羟丁酸、葡萄糖和胰岛素。SHF 处理的空气速度比对照和 SH 处理分别高出 0.56 至 0.83m/s（P<0.01），而对照处理的空气温度比 SH 和 SHF 处理分别高出 1.2 至 3.2°C（P<0.01）。对照处理的犊牛 RT 比 SH 和 SHF 处理分别高出 0.1 至 1.1°C（P≤0.03），而对照处理的 RF 比 SH 和 SHF 处理分别高出 39.4 至 60.2mov/min（P<0.01）。处理方式（P≥0.27）对饲料效率以及代谢物和胰岛素浓度没有影响，但在断奶时，对照组的犊牛比 SHF 组的犊牛短 2.6cm（P=0.03）。在牛舍中为犊牛提供风扇降低了 RT 和 RF，但对肩高只有微小的影响。
