**3. Effect of heat stress on animal productivity**

High ambient temperatures depress body activities which viewed homeostatically are biological mechanism for preventing overheating. The climatic condition also affect the amount of food and water intake, the availability of the potential energy in the ingested forage, the animals heat production system, the net energy available for productivity and the body composition of growing animal (Hafez, 1968).

Pulse rate which is expressed in beats per minutes is like the respiratory rate inversely proportional to the weight (W) of the animal, it can also alter rapidly due to external factor such as temperature or intense activity by the animal itself. Bianca and Findlay (1962) showed that exposure of sheep to severe heat for a short period increased pulse rate but exposure to relatively long period decreased pulse rate. Pulse rate is usually higher in small animals than in large animals due to the relatively high metabolic rate of small species (Bianca, 1968).

Respiratory rate can change rapidly and at the extreme, in a matter of minutes. It is indirectly influenced by the animal's activity and by environmental being inversely proportional to the volume of the animal.

Rectal temperature is taken to be equivalent to the body temperature. Body temperature is the best indicator of the good health of the animal and its variation above and below normal is a measure of the animal's aptitude to resist hardship factors of the environment.
