Dado-Senn Bethany, Van Os Jennifer, Dorea Joao, Laporta Jimena
Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, 53597.
JDS Commun. 2023 Oct 6;5(1):61-66. doi: 10.3168/jdsc.2023-0390. eCollection 2024 Jan.
Although active ventilation via fans is an effective and widely adopted heat abatement method for use with adult dairy cattle, it has yet to be investigated in outdoor hutch-housed dairy calves despite most US calves being raised in such systems. We investigated a solar-powered fan system for outdoor calf hutches and its effect on hutch microclimate and calf thermoregulation. During summer, a 3 × 3 Latin square was replicated 4 times (n = 12 preweaning heifers) with 4-d exposure periods to minimally (CON; rear windows closed), passively (PASS; rear windows opened), or actively (ACT; solar-powered fan, activated at dry bulb temperature [T] > 21°C) ventilated hutch systems. Hutch microclimate and calf thermoregulation were evaluated either continuously (T, humidity, rectum surface temperature, and behavior) or after a daily 30-min inside restriction (air speed, air particle number, noise level, respiration, and sweating rate, and skin and rectal temperature). Active ventilation substantially increased hutch air speed relative to PASS and CON (1.76 vs. 0.19 vs. 0.05 m/s). However, PASS hutches had the lowest INT T (27.2 vs. 26.4 vs. 27.8°C), whereas ACT INT T was reduced at 0900 and 1000 h relative to CON but not PASS. Similarly, ACT reduced calf respiration rates and lowered rectum surface temperature at 0800 and 0900 h when compared with CON but not PASS. The lack of strong ACT influence on calf outcomes over PASS could partially be explained by the decreased proportion of time ACT calves spent inside their hutch (48.7 vs. 67.3 vs. 64.1% of each hour). Overall, ACT improved hutch microclimate and calf responses relative to CON but not PASS. Either ACT or PASS ventilation may be sufficient to provide heat abatement to continental hutch-housed calves.
尽管通过风扇进行主动通风是一种有效且广泛应用于成年奶牛的降温方法，但在美国，大多数犊牛是在户外棚舍饲养的，而这种方法在户外棚舍饲养的犊牛中尚未得到研究。我们研究了一种用于户外犊牛棚舍的太阳能风扇系统及其对棚舍小气候和犊牛体温调节的影响。在夏季，采用3×3拉丁方设计，重复4次（n = 12头断奶前小母牛），每个暴露期为4天，分别设置为最低通风（CON；后窗关闭）、被动通风（PASS；后窗打开）或主动通风（ACT；太阳能风扇，在干球温度[T] > 21°C时启动）的棚舍系统。对棚舍小气候和犊牛体温调节进行连续评估（温度、湿度、直肠表面温度和行为），或在每天限制在棚舍内30分钟后进行评估（风速、空气颗粒数、噪音水平、呼吸、出汗率以及皮肤和直肠温度）。与PASS和CON相比，主动通风显著提高了棚舍风速（分别为1.76、0.19和0.05米/秒）。然而，PASS棚舍的室内平均温度最低（分别为27.2、26.4和27.8°C），而ACT组在0900和1000时的室内平均温度相对于CON降低，但相对于PASS没有降低。同样，与CON相比，ACT在0800和0900时降低了犊牛呼吸频率并降低了直肠表面温度，但相对于PASS没有降低。与PASS相比，ACT对犊牛各项指标缺乏显著影响，部分原因可能是ACT组犊牛在棚舍内停留的时间比例降低（每小时分别为48.7%、67.3%和64.1%）。总体而言，相对于CON，ACT改善了棚舍小气候和犊牛的反应，但相对于PASS没有改善。ACT或PASS通风都可能足以给大陆地区棚舍饲养的犊牛提供降温效果。
