Ammer S, Lambertz C, Gauly M
Department of Animal Sciences, Georg-August-University, 37075 Goettingen, Germany.
Faculty of Science and Technology, Free University of Bolzano, 39100 Bolzano, Italy.
J Dairy Sci. 2016 Dec;99(12):10067-10076. doi: 10.3168/jds.2016-11282. Epub 2016 Sep 21.
The present study investigated whether reticular temperature (RT) in dairy cattle is a useful indicator of heat stress considering the effects of milk yield and water intake (WI). In total, 28 Holstein-Friesian dairy cows raised on 3 farms in Lower Saxony, Germany, were studied from March to December 2013. During the study, RT and barn climate parameters (air temperature, relative humidity) were measured continuously and individual milk yield was recorded daily. Both the daily temperature-humidity index (THI) and the daily median RT per cow were calculated. Additionally, the individual WI (amount and frequency) of 10 cows during 100d of the study was recorded on 1 farm. Averaged over all farms, daily THI ranged between 35.4 and 78.9 with a mean (±standard deviation) of 60.2 (±8.7). Dairy cows were on average (±standard deviation) 110.9d in milk (±79.3) with a mean (±standard deviation) milk yield of 35.2kg/d (±9.1). The RT was affected by THI, milk yield, days in milk, and WI. Up to a THI threshold of 65, RT remained constant at 39.2°C. Above this threshold, RT increased to 39.3°C and further to 39.4°C when THI ≥70. The correlation between THI ≥70 and RT was 0.22, whereas the coefficient ranged between r=-0.08 to +0.06 when THI <70. With increasing milk yield, RT decreased slightly from 39.3°C (<30kg/d) to 39.2°C (≥40kg/d). For daily milk yields of ≥40kg, the median RT and daily milk yield were correlated at r=-0.18. The RT was greater when dairy cows yielded ≥30kg/d and THI ≥70 (39.5°C) compared with milk yields <30kg and THI <70 (39.3°C). The WI, which averaged (±standard deviation) 11.5 l (±5.7) per drinking bout, caused a mean decrease in RT of 3.2°C and was affected by the amount of WI (r=0.60). After WI, it took up to 2h until RT reached the initial level before drinking. In conclusion, RT increased when the THI threshold of 65 was exceeded. A further increase was noted when THI ≥70. Nevertheless, the effects of WI and milk yield have to be considered carefully when RT is used to detect hyperthermia in dairy cattle.
本研究探讨了考虑到产奶量和饮水量（WI）的影响，奶牛的网状温度（RT）是否是热应激的有用指标。2013年3月至12月，对德国下萨克森州3个农场饲养的28头荷斯坦-弗里生奶牛进行了研究。研究期间，连续测量RT和牛舍气候参数（气温、相对湿度），并每日记录个体产奶量。计算每日温湿度指数（THI）和每头奶牛的每日RT中位数。此外，在1个农场记录了10头奶牛在研究的100天内的个体饮水量（数量和频率）。所有农场的平均每日THI在35.4至78.9之间，平均（±标准差）为60.2（±8.7）。奶牛平均（±标准差）产奶110.9天（±79.3），平均（±标准差）产奶量为35.2千克/天（±9.1）。RT受THI、产奶量、产奶天数和饮水量的影响。在THI阈值为65之前，RT保持在39.2°C不变。超过该阈值后，当THI≥70时，RT升至39.3°C，进一步升至39.4°C。THI≥70与RT之间的相关性为0.22，而当THI<70时，系数在r=-0.08至+0.06之间。随着产奶量增加，RT从39.3°C（<30千克/天）略有下降至39.2°C（≥40千克/天）。对于每日产奶量≥40千克的情况，RT中位数与每日产奶量的相关性为r=-0.18。与产奶量<30千克且THI<70（39.3°C）相比，产奶量≥30千克且THI≥70（39.5°C）时奶牛的RT更高。每次饮水平均（±标准差）为11.5升（±5.7），导致RT平均下降3.2°C，且受饮水量的影响（r=0.60）。饮水后，RT需要长达2小时才能达到饮水前的初始水平。总之，当超过THI阈值65时，RT升高。当THI≥70时，RT进一步升高。然而，在使用RT检测奶牛热应激时，必须仔细考虑饮水量和产奶量的影响。
