Physiological indices in buffaloes exposed to sun.

Abstract

ABSTRACT Ten lactating buffaloes were kept in a barn or exposed to direct solar radiation (air temperature 30.2 0 C) for 12 h. Rectal temperature (RT) and respiratory rate (RR) were measured at 8 h, 11 h, 15 h and 20 h. Both RT and RR increased significantly at temperature -humidity index (THI) -77.83, showing that the lactating buffaloes are sensitive to heat stress and are not able to maintain their core temperature within the thermoneutral zone. The same THI had no significant effect on rectal temperature elevation when the buffaloes were kept in barn. The obvious heat stress, assessed by the rate of RT and RR elevations, was not accompanied with an enhancement of plasma cortisol level. The unchanged plasma cortisol level in the buffaloes under heat is interpreted within the context of the hormonal integration and the modulating effect of hypothalamic-pituitary-adrenal axis on the other endocrine glands involved in the thermal homeostasis maintenance. These data demonstrate that lactating buffaloes need protection against the direct solar radiation