Environmental and behavioral sensor data to identify heat stress in dairy cows

Heat stress impairs the health and performance of dairy cows, yet only a few studies have investigated the diversity of cattle behavioral responses to heat waves. This research was conducted on an Italian Holstein dairy farm equipped with precision livestock farming sensors to assess potential different behavioral patterns of the animals. Three heat waves, defined as at least five consecutive days with mean daily temperature-humidity index higher than 72, were recorded in the farm area during the summer of 2021. Individual daily milk yield data of 102 cows were used to identify ‘heat-sensitive’ animals, meaning the cows that, under a given heat wave, experienced a milk yield drop that was not linked with other health events (e.g., mastitis). Milk yield drops were detected as perturbations of the lactation curve estimated by iteratively using Wood’s equation. Individual daily minutes of lying, chewing, and activity were retrieved from ear-tag-based accelerometer sensors. Semi-parametric generalized estimating equations models were used to assess behavioral deviations of heat-sensitive cows from the herd means under heat stress conditions. Heat waves were associated with an overall increase in the herd’s chewing and activity times, along with an overall decrease of lying time. Heat-sensitive cows spent approximately 15 min/d more chewing and performing activities (p < 0.05). The findings of this research suggest that the information provided by high-frequency sensor data could assist farmers in identifying cows for which personalized interventions to alleviate heat stress are needed.

热应激 (heat stress) 会损害奶牛的健康与生产性能，但目前仅有少数研究探讨了牛群对热浪行为反应的多样性。本研究依托一座配备精准畜牧养殖 (precision livestock farming) 传感器的意大利荷斯坦奶牛场开展，旨在探究受试奶牛的潜在行为模式差异。2021年夏季，该养殖场所在区域共记录到3次热浪事件，热浪的判定标准为连续至少5天的日均温湿度指数 (temperature-humidity index, THI) 高于72。研究选取102头奶牛的个体单日产奶量数据，用于识别热敏感 (heat-sensitive) 奶牛——即指在任意一次热浪期间出现产奶量下降，但未伴随乳腺炎 (mastitis) 等其他健康异常事件的奶牛。产奶量下降的识别通过迭代应用伍德方程 (Wood’s equation) 拟合泌乳曲线，以定位泌乳曲线的异常扰动实现。研究人员从基于耳标的加速度传感器 (accelerometer sensors) 中，提取了每头奶牛每日躺卧、咀嚼与活动的时长数据。本研究采用半参数广义估计方程 (semi-parametric generalized estimating equations) 模型，评估热应激条件下热敏感奶牛的行为表现与牛群平均水平的偏离程度。数据分析结果显示，热浪事件与牛群整体的咀嚼时长、活动时长增加存在关联，同时伴随躺卧时长的整体下降。热敏感奶牛的每日咀嚼与活动时长较牛群平均水平多出约15 min/d (p < 0.05)。本研究结果表明，高频传感器数据所提供的信息，可帮助养殖户识别需要采取个性化干预措施以缓解热应激的奶牛。