Effects of heat challenge on growth performance, ruminal, blood and physiological parameters of Chinese crossbred goats

The aim of this study was to evaluate the effects of heat challenge on growth performance as well as ruminal, blood and physiological parameters of Chinese crossbred goats. During the heat challenge period, the goats exhibited significantly higher skin temperatures, pulse rates and respiration rates than during the control period. The rumen pH and concentrations of ammonia-N (NH3-N), total volatile fatty acids (TVFAs), acetic acid and propionic acid were significantly lower during the heat challenge period than during the control period. In addition, the butyric acid concentration, acetate "to-propionate ratio (A/P ratio) and oxidation-reduction potential (ORP) in the rumen were significantly increased in heat-challenged goats compared to those in control period. During the heat challenge period, the goats showed significantly higher serum creatine kinase (CK) activity and blood urea nitrogen (BUN) and malonaldehyde (MDA) concentrations than during the control period, while the glutathione peroxidase (GSH-Px) activity and the serum total protein (TP) and vitamins C and E concentrations were significantly lower (P < 0.05) during the control period. During the heat challenge period, the goats exhibited significantly lower (P < 0.05) dry matter (DM) intake (DMI) and average daily gain (ADG) than during the control period and significantly higher (P < 0.05) digestibilities of DM, neutral detergent fiber (NDF) and acid detergent fiber (ADF) than during the control period. These results suggest that the effect of a heat challenge on goats is systemic. Therefore, in goat production practices, the adverse effects of heat stress should not be ignored.