Buffalo's biological functions as affected by heat stress - A review

Buffaloes are well suited to hot and humid climates and muddy terrain, but they exhibit signs of great distress when exposed to direct solar radiation or when working in the sun during hot weather. This is due to the fact that buffalo bodies absorb a great deal of solar radiation because of their dark skin and sparse coat or hair, and in addition to that they possess a less efficient evaporative cooling system due to their rather poor sweating ability. Particularly, exposure of buffaloes to the latter conditions evokes a series of drastic changes in biological functions that include depression in feed intake, efficiency and utilization, disturbances in metabolism of water, protein. energy and mineral balances, enzymatic reactions, hormonal secretions and blood metabolites. Such changes result in impairment of growth, production and reproduction performance. The effect of heat stress is aggravated when heat stress is accompanied by high ambient humidity. The body temperature of buffaloes in the hot sun could only be kept normal in the shade or by wallowing or by quasi-continuous application of water, preferably with an air draft or wind to dry it off. In shade or in wallow, buffaloes cool off quickly, perhaps because their black skin, which is rich in blood vessels. conducts and radiates heat efficiently, but buffaloes cool off more quickly than cattle in the shade. Particularly, experience has shown that wallowing is not essential. The buffalo's adaptability to the desert sub-tropical environment of Egypt was estimated as 89.6 and 89.1\% in two different studies. Adaptability estimation for Friesian cows was 82.9\%. It seems that the buffalo has a greater tolerance of cold weather than is commonly supposed due to its exposure to cold stress in some of the cold areas in which it exists in the world. However, there are no studies available on the tolerance of buffaloes to cold stress. (C) 2009 Published by Elsevier B.V.