School of Agricultural Sciences, College of Environmental and Life Sciences, Murdoch University, Murdoch, WA, Australia.
School of Veterinary Medicine, College of Environmental and Life Sciences, Murdoch University, Murdoch, WA, Australia.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae332.
There is increasing interest from cattle lot-feeders in the use of shade to mitigate the effects of a potential heat-stress event, though it is unclear whether the reported benefits of shade in previous studies conducted in more high-risk heat-stress zones are pertinent in cooler temperate zones. The objectives of this study were to measure the welfare and performance benefits of shade provision for lot-fed cattle at a commercial feedlot located in a mild heat-stress risk zone in Western Australia. Six blocks of black Angus (Bos taurus) steers were inducted into the feedlot over 6 time windows across a southern hemisphere summer, with 80 cattle per block housed in a partially shaded pen (providing 3.125 m2 of shade per animal) and 80 in an unshaded pen. Parameters assessed in 960 cattle over the first 70 d in the feedlot included weight gain, feed intake, and physiological and behavioral indices of overall health and welfare. Over the months of October to May in which the experiment was conducted, shaded cattle demonstrated a modest 0.13 kg overall increase in average daily gain across the 70-d feedlot period (P = 0.13). There was no difference in dry matter intake between any block or treatment. The physiological and behavioral markers of health and welfare revealed that, even during to the hottest times of the experiment, the cattle were quite able to thermoregulate, via increased panting and seeking shade (if available), to maintain physiological homeostasis. In addition, we measured the effect of heat stress and shade provision on the affective state of the cattle. Qualitative behavioral assessment was used to indicate that the cattle in the "no stress" temperature humidity index (THI) category and the shaded cattle in the "moderate stress" THI category displayed the most positive demeanor (P < 0.05), being described as more "settled and sociable", while the unshaded cattle in the "moderate stress" THI category and all cattle in the "severe stress" THI category were described as more "agitated/anxious" (P < 0.05). Overall, the findings from the present study suggest that there are definite welfare and modest performance benefits associated with providing cattle with shade in summer in a feedlot situated in a temperate climatic zone.
越来越多的牛场饲养者对使用遮阳来减轻潜在热应激事件的影响感兴趣，尽管尚不清楚在更高温应激风险地区进行的先前研究中报告的遮阳益处是否与较凉爽的温带地区有关。本研究的目的是测量在位于西澳大利亚温和热应激风险地区的商业饲养场为牛场饲养的牛提供遮荫的福利和性能益处。在南半球夏季的 6 个时间窗口中，将 6 个块的黑色安格斯（Bos taurus）阉牛引入饲养场，每个块中的 80 头牛被安置在部分遮荫的围栏中（每头动物提供 3.125 平方米的遮荫），80 头牛被安置在无遮荫的围栏中。在饲养场的头 70 天中，对 960 头牛进行了评估，包括体重增加、饲料摄入量以及整体健康和福利的生理和行为指标。在进行实验的 10 月至 5 月期间，遮荫牛在 70 天的饲养场期间的平均日增重平均增加了 0.13 公斤（P=0.13）。任何一个块或处理之间的干物质摄入量都没有差异。健康和福利的生理和行为标志物表明，即使在实验最热的时候，牛也能够通过增加喘气和寻找遮荫（如果有的话）来调节体温，以维持生理平衡。此外，我们还测量了热应激和遮荫对牛的情感状态的影响。定性行为评估用于表明处于“无应激”温度湿度指数（THI）类别的牛和处于“中度应激”THI 类别的遮荫牛表现出最积极的举止（P<0.05），被描述为更“安定和善于交际”，而处于“中度应激”THI 类别的无遮荫牛和处于“严重应激”THI 类别的所有牛则被描述为更“激动/焦虑”（P<0.05）。总体而言，本研究的结果表明，在温带气候区的饲养场中，夏季为牛提供遮荫确实有明确的福利和适度的性能益处。
