Heat stress plays a role in livestock production in warm climates. Heat stress conditions impair animal welfare and compromise the productive and reproductive performance of dairy cattle. Under heat stress conditions, dairy cattle modify their behavior. Thus, the assessment of behavior alterations can be an indicator of environmental or physiological anomalies. Moreover, precision livestock farming allows for the individual and constant monitoring of animal behavior, arising as a tool to assess animal welfare. The purpose of this study was to evaluate the effect of heat stress on the behavior of dairy cows using activity sensors. The study was carried out in Tinajeros (Albacete, Spain) during the summer of 2020. Activity sensors were installed in 40 cows registering 6 different behaviors. Environmental conditions (temperature and humidity) were also monitored. Hourly data was calculated for both animal behavior and environmental conditions. Temperature and Heat Index (THI) was calculated for each hour. The accumulated THI during the previous 24 h period was determined for each hour, and the hours were statistically classified in quartiles according to the accumulated THI. Two groups were defined as Q4 for no stress and Q1 for heat stress. The results showed that animal behavior was altered under heat stress conditions. Increasing THI produces an increase in general activity, changes in feeding patterns and a decrease in rumination and resting behaviors, which is detrimental to animal welfare. Daily behavioral patterns were also affected. Under heat stress conditions, a reduction in resting behavior during the warmest hours and in rumination during the night was observed. In conclusion, heat stress affected all behaviors recorded as well as the daily patterns of the cows. Precision livestock farming sensors and the modelling of daily patterns were useful tools for monitoring animal behavior and detecting changes due to heat stress.

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热应激下的奶牛活动：西班牙的案例研究

热应激在温暖气候下的牲畜生产中发挥作用。热应激条件会损害动物福利并损害奶牛的生产和繁殖性能。在热应激条件下，奶牛会改变它们的行为。因此，对行为改变的评估可以是环境或生理异常的指标。此外，精准畜牧业允许对动物行为进行个体化和持续监测，作为评估动物福利的工具。本研究的目的是使用活动传感器评估热应激对奶牛行为的影响。该研究于 2020 年夏季在 Tinajeros（西班牙阿尔巴塞特）进行。活动传感器安装在 40 头奶牛身上，记录了 6 种不同的行为。还监测了环境条件（温度和湿度）。计算动物行为和环境条件的每小时数据。每小时计算温度和热指数 (THI)。每小时测定前 24 小时内累积的 THI，并根据累积的 THI 将小时数按四分位数进行统计分类。两组被定义为无压力的 Q4 和热应激的 Q1。结果表明，动物行为在热应激条件下发生了改变。增加 THI 会导致一般活动增加、喂养模式改变以及反刍和休息行为的减少，这对动物福利有害。日常行为模式也受到影响。在热应激条件下，观察到最热时间的休息行为和夜间的反刍行为减少。总之，热应激影响了所有记录的行为以及奶牛的日常模式。精确的畜牧养殖传感器和日常模式建模是监测动物行为和检测热应激引起的变化的有用工具。