Calorigenesis of Cattle as Influenced by Hydrocortisone and Environmental Temperature

Abstract

Five Holstein cows were used to determine the effect of hydrocortisone on calorigenesis at 18° and 35° C. The objective of the study was to determine the calorigenic action, latent period and biological effective time of hydrocortisone at different environmental temperatures. The intravenous injection of hydrocortisone significantly increased resting or standing heat production and in pulse rate in animals maintained at either 18° or 35° C. The latent period was found to be 3 to 4 hr. at 18° C. and 2 to 3 hr. at 35° C. The biological effective time was estimated to be 3 and 5 hr. at the comfort temperature (18° C.) and under exposure to heat (35° C), respectively. High temperature (35° C.) decreased pulse rate, heat production and feed intake, and increased respiration rate and rectal temperature, indicating a disturbance in thermal equilibrium.