Effect of heat-stress on some physiological and biochemical parameters in buffaloes

The experiment has been carried out with 10 lactating buffaloes (Bulgarian Murrah breed) in an interval of two successive days. They were kept in shade(first day) and exposed to direct solar radiation (second day) with ambient temperature not less than 30 degrees C for 12 h. Rectal temperature(RT) and respiratory rate (RR) were measured at 8 a.m., 11 a.m., 3 p.m. and 8 p.m. 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 the barn. These data demonstrate that lactating buffaloes need protection against direct solar radiation. Plasma cholesterol and total protein levels tended to be lower during the exposure to direct solar radiation compared to the morning levels. Plasma urea level increased and plasma indol level remained unchanged when the buffaloes were exposed to sun. It is suggested that the level of the first three parameters is closely related with the dynamic of cortisol and blood volume fluctuation in animals under heat.