Van Laer E, Moons C P H, Ampe B, Sonck B, Vandaele L, De Campeneere S, Tuyttens F A M
1Institute for Agricultural and Fisheries Research (ILVO),Animal Sciences Unit,Scheldeweg 68,9090 Melle,Belgium.
2Faculty of Veterinary Medicine,Ghent University,Salisburylaan 133,9820 Merelbeke,Belgium.
Animal. 2015 Sep;9(9):1536-46. doi: 10.1017/S1751731115000804. Epub 2015 May 21.
Using behavioural indicators of thermal discomfort, that is, shade seeking, panting scores (PS) and respiration rate (RR), we evaluated the effect of hot summer conditions and shade, for a herd of adult Holstein dairy cows and a herd of Belgian Blue beef cows kept on pasture in a temperate area (Belgium). During the summer of 2012, both herds were kept on pasture without access to shade (NS). During the summers of 2011 and 2013 each herd was divided into one group with (S) and one without (NS) access to shade. Shade was provided by young trees with shade cloth (80% reduction in solar radiation) hung between them. For S cows, we investigated how shade use was related to hot conditions as quantified by six climatic indices. The heat load index (HLI), which incorporates air temperature and humidity, solar radiation and wind speed, was the best predictor of the six indices tested. In 2011, there was a relatively high threshold for use of shade. When HLI=90, shade use probability reached 17% for dairy cows and 27% for beef cows. In 2013, however, at HLI=90, shade use probability reached 48% for dairy cows and 41% for beef cows. For animals from the NS treatment we determined the effect of hot summer conditions on RR and PS (with 0=no panting and 4.5=extreme panting). In both types of cattle, an increase in black globe temperature was the best predictor for increasing RR and PS. Furthermore, we determined how the effect of hot summer conditions on RR and PS was affected by the use of shade. Under hot conditions (black globe temperature ⩾ 30°C), >50% of the animals under shade retained normal PS and RR (PS<1 and RR<90 breaths per minute), whereas normal RR and PS were significantly less prevalent for animals outside shade. Our findings suggest that, even in temperate summers, heat can induce thermal discomfort in cattle, as evidenced by increases in shade use, RR and PS, and that shade increases thermal comfort.
我们运用热不适行为指标，即寻找阴凉处、气喘评分（PS）和呼吸频率（RR），评估了炎热夏季条件及阴凉处对一群成年荷斯坦奶牛和一群比利时蓝肉牛的影响，这些牛群饲养在温带地区（比利时）的牧场。在2012年夏季，两个牛群都饲养在无阴凉处的牧场（NS）。在2011年和2013年夏季，每个牛群都被分为一组有阴凉处（S）和一组无阴凉处（NS）的牛群。阴凉处由幼树提供，树之间挂着遮阳布（太阳辐射减少80%）。对于有阴凉处的牛，我们研究了阴凉处的使用与通过六个气候指标量化的炎热条件之间的关系。综合气温、湿度、太阳辐射和风速的热负荷指数（HLI）是所测试的六个指标中最佳的预测指标。2011年，阴凉处使用的阈值相对较高。当热负荷指数（HLI）=90时，奶牛使用阴凉处的概率达到17%，肉牛达到27%。然而，在2013年，当热负荷指数（HLI）=90时，奶牛使用阴凉处的概率达到48%，肉牛达到41%。对于无阴凉处处理的动物，我们确定了炎热夏季条件对呼吸频率（RR）和气喘评分（PS）的影响（0表示无气喘，4.5表示极度气喘）。在两种类型的牛中，黑球温度升高是呼吸频率（RR）和气喘评分（PS）增加的最佳预测指标。此外，我们确定了炎热夏季条件对呼吸频率（RR）和气喘评分（PS）的影响如何受到阴凉处使用的影响。在炎热条件下（黑球温度⩾30°C），>50%处于阴凉处的动物保持正常的气喘评分（PS）和呼吸频率（RR）（PS<1且RR<每分钟90次呼吸），而阴凉处外的动物正常的呼吸频率（RR）和气喘评分（PS）明显不那么普遍。我们的研究结果表明，即使在温带夏季，热也会导致牛的热不适，这表现为阴凉处使用、呼吸频率（RR）和气喘评分（PS）的增加，并且阴凉处可提高热舒适度。
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