ARIMA modeling for predicting hair coat temperature in dairy cows under heat stress¹

Modelagem ARIMA para previsão da temperatura do pelame em vacas de leite sob estresse térmico

Hair coat temperature is an effective indicator for monitoring heat stress in dairy cows, particularly in tropical regions, as it directly reflects environmental conditions and animal adaptation. Autoregressive Integrated Moving Average models with transfer functions enable dynamic assessment of the relationship between environmental variables and physiological responses. This study evaluated the influence of the temperature-humidity index and ambient temperature on hair coat temperature, as well as its temporal response to heat stress, considering differences related to age and parity. Hair coat temperature was measured at the head, back, udder, and cannon bone of 19 Holstein cows housed in a free-stall system, twice daily over 229 days. The model was fitted to the input series to predict the output series (hair coat temperature). Seasonal conditions significantly affected hair coat temperature, and cross-correlation analysis indicated a rapid thermal response to heat stress with short-term persistence, generally between 24 and 48 hours. Ambient temperature showed a significant causal relationship with hair coat temperature, and the transfer function model demonstrated good predictive performance (Root Mean Square Error = 1.08 °C). Younger cows and those with lower parity were more thermally vulnerable, whereas adult, multiparous cows showed greater thermal stability. Predictive modeling proved to be a promising tool for studying the thermal dynamics of Holstein cows. However, the results are limited to this breed and the local climatic conditions and should not be extrapolated to other production contexts.

Key words:
transfer function; seasons; cross-correlation; lagged response; free stall

ARIMA models accurately predict hair coat temperature in Holstein cows under intense heat stress conditions.

Seasonal factors, such as ambient temperature and the temperature-humidity index, influence bovine coat temperature.

Younger and primiparous cows are more susceptible to heat stress than multiparous cows.