Wednesday 20 February 2019

Dairy and veterinary journals-Lupine Publishers

Thermal stress or heat stress can be defined as the sum of external forces to a homoeothermic animal that acts to displace body temperature from the resting state. Such a stress can disrupt the physiologic and productive performance of an animal. The increase in body temperature caused by heat stress has direct, adverse consequences on cellular functions. The livestock’s by homeotherms to the stabilize body temperature within fairly narrow limits is essential to control biochemical reactions and physiological processes within normal metabolism [1]. In order to maintain homeothermy, an animal must be in thermal equilibrium with its environment, which includes radiation, air temperature, air movement and humidity. Body temperature is regulated by modulation of metabolic heat production and heat loss from the body through sensible and insensible means. The deviation in ambient temperature below or above the thermoneutral zone (5- 250C) causes thermal stress to the animals. Cattle and buffaloes can maintain their physiological processes within the normal limits in an ambient temperature of 5-250C [2]. Hot humid season is more stressful to livestock species compared to hot dry season mainly due to lower evaporate and heat loss from the animal body. The evaporate heat loss takes place through respiratory tract (panting) and skin surface (sweating) in animals. Nonevaporate heat exchange occurs through conduction, convection and radiation and depends on temperature gradients between animal and surrounding environment and vice versa. Heat stress causes behavioral and metabolic changes and thereby reduces feed intake and metabolic activity and ultimately decline in animal’s productivity.

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