Adaptation to heat in pig production: the genetic pathway
Résumé
Heat stressed pigs reduce their feed intake which impair their growth or reproduction performances. Management
solutions are available to attenuate the effect of heat stress on pigs, such as environmental solutions (water or
feeding management). However, these solutions are technically and economically difficult to implement. The
genetic selection for improving environmental adaptation in pig production is the most promising long term
option.
The PigHeaT project aims 1) at identifying QTLs for heat adaptation, by examining direct responses to find genes
involved in metabolic ways, indirect responses to find genes affecting growth or robustness to environmental
variations, 2) at better understanding the physiological mechanisms underlying heat adaptation. The PigHeaT
project (http://www6.inra.fr/pigheat_eng/) is based on original biological resources and original experimental
facilities. The studied population will be a backcross between Large White pigs, productive but poorly
thermotolerant breed, and Creole pigs, low productive but highly thermotolerant breed. The progeny issued from
this backcross will express all possible levels of thermal tolerance and production performances when submitted to
heat stress, depending on the alleles received from their parents. High throughput phenotyping, metabolomics on
all the progeny, and transcriptomics on a subset of extreme pigs selected on thermal tolerance response, will be
applied. The design benefits from the unique combination of experimental facilities available at INRA: the first
part of the project will rely on the backcross population raised in the experimental facilities located in the West
Indies (Guadeloupe, tropical environment). The concomitant production of the same population in the
experimental facilities available in temperate France (Charente Maritime) will allow the detection of genetic by
environment (GxE) effects for the QTL detected in Guadeloupe.
The first phenotypic results confirm the effect of environment on zootechnical and thermoregulatory pig
performance. A significant effect of the production environment has been observed on pig’s growth rate, with a
difference of about 100 g / d for the temperate environment (820 vs 720 g / d in the tropics) and lower body
temperatures (39.4 and 34.8 ° C for rectal and skin temperatures vs. 39.5 and 35.9 ° C in the tropics).