Quantify and compare the full-day and 24-h behavioral features of dairy cows related to the environmental temperature and humidity

Heat stress severely impacts the health, production, and reproduction of dairy herds. Daily behavioral features of dairy herds were generally associated with the temperature-humidity index (THI) to assess the onset of heat stress in previous studies. The 24-h behavioral features, describing the behaviors within a day, are less studied and could be superior indicators for heat stress than daily behavioral features. In this study, the meteorological data and behavioral data including lying time, steps, and transition changes in 15-min intervals in 2019 were retrieved from 8 dairy farms. Herd days of 8 farms were divided into (1) herd days with daytime pasture and (2) herd days without pasture access, and subsequently labeled with 3 THI classes: 1 (THI ≤ 58), 2 (58 < THI < 64) or 3 (THI ≥ 64). Eighteen behavioral features were engineered based on the visualization of 24-h behavioral patterns in 3 THI classes and were associated with daily THI using correlation analysis and general linear models. In contrast with daily behavioral features, the 24-h features, describing nighttime lying, daytime step, and daytime transition, had consistently significant correlation coefficients with daily THI across farms in the herd days with daytime pasture access. There was an interaction of THI class with farm for all engineered features in herd days with daytime pasture access. These results indicate that dairy cow behaviors are affected by both THI and farm, and 24-h behavioral features have a more consistent correlation with THI across farms compared with daily behavioral features.