Physiological and behavioral indicators of water buffaloes with access to heat mitigation resources in a grazing system during the hot season in the subtropics

Abstract

Water buffaloes are increasingly being raised in similar way to dairy cows, in grazing systems frequently deprived of shade and water for immersion. This study aimed to evaluate the effects of different heat mitigation resources, 1) only shade and 2) shade plus water for immersion, on the behavioral repertoire and physiological characteristics of female grazing buffaloes in the subtropics during the hot season. Twenty buffaloes (Bubalus bubalis), including calves, heifers and non-lactating cows were allocated throughout the hot season (from December 2021 to April 2022) in a grazing system with two different heat mitigation resources (treatments): only shade (SH) and shade plus water for immersion (SHW). Diurnal behavioral repertoire was recorded every 15 days, individually and focally, at every 5 minutes for 12 hours per day. Heart rate (HR; beats/min), respiration rate (RR; breaths/min), rectal temperature (RT; °C) and panting score were also measured. Buffaloes reduced grazing time especially with THI above 75. Buffaloes at SHW spent more time grazing and lying than SH buffaloes (P < 0.05). Cows and heifers had higher ruminating (P < 0.05) and standing time (P < 0.05) compared with calves. Physiological variables did not differ (P > 0.05) between treatments (SH vs. SHW) and were positively correlated with air temperature and THI (P < 0.05). HR was higher for heifers (59.6) and calves (63.5) than for cows (53.3; P < 0.05). RT tended to be higher for heifers (38.4) and calves (38.3) than for cows (38.1; 0.05 < P < 0.10). However, respiration rate did not differ across buffalo categories (P > 0.05). Panting behavior was not reported throughout the observation days (panting score = 0). When both heat mitigation resources, shade and water for immersion were available, buffaloes preferred water for immersion to mitigate the effects of heat stress. Regardless animal category, buffaloes were able to maintain physiological variables within the normal range, indicating that providing shade and/or water for immersion, as environmental enrichment resources for thermoregulation, is suitable for heat stress mitigation in water buffaloes throughout the hot season in the subtropics.