Attenuate the effects of high ambient temperature on pig performance : the genetic selection

Abstract

Ambient temperature is one of the most important climatic factors affecting pig performances in the summertime in temperate areas and throughout the year in tropical areas. Exposure to high ambient temperature directly affects male and female reproduction function and indirectly affects lactation and growth performance via a reduced voluntary feed intake. After a short presentation of the mechanisms implied in thermoregulation and the effects of high ambient temperature on pig performance according to the physiological state, this review focuses on the methods that could be used to reduce the negative effect of heat stress and it also highlights on the possibilities for genetic improvement of heat tolerance. To establish whether the selection of pigs for heat stress is feasible, the physiological mechanisms implied in heat adaptation processes and the relationship between adaptation and production traits must be better understood. This first step is necessary to choose the best selection criteria and breeding program for the genetic improvement of heat tolerance. In contrast to other species (ruminant and chickens), genetic diversity for heat tolerance within or between breed and potential selection criteria are little known in the pig. However, some indicators of heat sensitivity (Heat Shock Protein), heat production (residual consumption, Uncoupling protein) or heat dissipation (respiratory rate, cutaneous heat conductivity) could be used as the selection criteria.