Vol. 7, Issue 4 (2018)

Author(s):
Subhashree Sarangi

Abstract:
In the environment, animals have to cope with a combination of natural factors. Extreme changes in these factors can alter homeostasis, which can lead to thermal or heat stress. This stress can be due to either high or low temperature. Energy transference for thermoregulation in homoeothermic animals occurs through several mechanisms: conduction, convection, radiation and evaporation. When animals are subjected to thermal stress, physiological mechanisms are activated which may include endocrine, neuroendocrine and behavioral responses. Activation of the neuroendocrine system affects the secretion of hormones and neurotransmitters which act collectively as response mechanisms that allow them to adapt to stress. Mechanisms which have developed through evolution to allow animals to adapt to high environmental temperatures and to achieve thermo-tolerance include physical, physiological and biochemical changes like reduced feed intake and metabolic heat production, increased surface area of skin to dissipate heat, increased blood flow to take heat from the body core to the skin and extremities to dissipate the heat, increased numbers and activity of sweat glands, panting, increased water intake and color adaptation of integument system to reflect heat. Chronic exposure to thermal stress can cause disease, reduce growth, decrease productive and reproductive performance and, in extreme cases, lead to death. This paper aims to briefly explain the physical and physiological responses of mammals to thermal stress, like a tool for biological environment adaptation, emphasizing knowledge gaps and offering some recommendations to stress control for the animal production system.