Shu Hang, Guo Leifeng, Bindelle Jérôme, Fang Tingting, Xing Mingjie, Sun Fuyu, Chen Xiaoyang, Zhang Wenju, Wang Wensheng
Agricultural Information Institute, Chinese Academy of Agricultural Sciences, 100086, Beijing, China.
AgroBioChem/TERRA, Precision Livestock and Nutrition Unit, Gembloux Agro-Bio Tech, University of Liège, 5030, Gembloux, Belgium.
Int J Biometeorol. 2022 Jun;66(6):1219-1232. doi: 10.1007/s00484-022-02270-w. Epub 2022 Mar 30.
This study aimed to better understand environmental heat stress and physiological heat strain indicators in lactating dairy cows. Sixteen heat stress indicators were derived using microenvironmental parameters that were measured at the surrounding of cows and at usual fixed locations in the barn by using handheld and fixed subarea sensors, respectively. Twenty high-producing Holstein-Friesian dairy cows (> 30.0 kg/day) from an intensive dairy farm were chosen to measure respiration rate (RR), vaginal temperature (VT), and body surface temperature of forehead (FT), eye (ET), and muzzle (MT). Our results show that microenvironments measured by the handheld sensor were slightly warmer and drier than those measured by the fixed subarea sensor; however, their derived heat stress indicators correlated equally well with physiological indicators. Interestingly, ambient temperature (T) had the highest correlations with physiological indicators and the best classification performance in recognizing actual heat strain state. Using segmented mixed models, the determined T thresholds for maximum FT, mean FT, RR, maximum ET, mean ET, VT, mean MT, and maximum MT were 24.1 °C, 24.2 °C, 24.4 °C, 24.6 °C, 24.6 °C, 25.3 °C, 25.4 °C, and 25.4 °C, respectively. Thus, we concluded that the fixed subarea sensor is a reliable tool for measuring cows' microenvironments; T is an appropriate heat stress indicator; FT, RR, and ET are good early heat strain indicators. The results of this study could be helpful for dairy practitioners in a similar intensive setting to detect and respond to heat strain with more appropriate indicators.
本研究旨在更好地了解泌乳奶牛的环境热应激和生理热应激指标。利用微环境参数得出了16个热应激指标，这些参数分别通过手持式传感器和固定分区传感器在奶牛周围以及牛舍中通常的固定位置进行测量。从一个集约化奶牛场挑选了20头高产荷斯坦 - 弗里生奶牛（日产奶量> 30.0千克），测量其呼吸频率（RR）、阴道温度（VT）以及额头（FT）、眼睛（ET）和口鼻部（MT）的体表温度。我们的结果表明，手持式传感器测量的微环境比固定分区传感器测量的微环境略温暖且干燥；然而，它们得出的热应激指标与生理指标的相关性同样良好。有趣的是，环境温度（T）与生理指标的相关性最高，并且在识别实际热应激状态方面具有最佳的分类性能。使用分段混合模型，确定的FT最大值、FT平均值、RR、ET最大值、ET平均值、VT、MT平均值和MT最大值的T阈值分别为24.1℃、24.2℃、24.4℃、24.6℃、24.6℃、25.3℃、25.4℃和25.4℃。因此，我们得出结论，固定分区传感器是测量奶牛微环境的可靠工具；T是合适的热应激指标；FT、RR和ET是良好的早期热应激指标。本研究结果有助于类似集约化环境中的奶牛从业者使用更合适的指标来检测和应对热应激。
