Adaptation to heat in pig production : the genetic pathway

"Chantier qualité spécifique "Auteurs Externes" département de Génétique animale : uniquement liaison auteur au référentiel HR-Access "; il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : REPORT; The climate is changing and according to the recent estimates from the IPCC, the likelihood of heatwave events is expected to increase both in number and in intensity. Temperature is projected toincrease from 1.8 to 4.0°C from 1980-1999 to 2090-2099. Hence, heat stress-related costs in pigproduction will be amplified in the future, both in temperate areas (summer heat waves) and tropicalareas (hot and humid environment). Meanwhile, world pig production is moving rapidly to tropicaland subtropical regions reaching now more than 50% of the total production. The world developmentof pig production has been achieved through improvement of animal genetics and management intemperate countries. However, selection performed in optimally controlled conditions has increasedthe sensitivity of animals to high ambient temperature. Heat stressed pigs reduce their feed intakewhich impair their growth or reproduction performances. Management solutions are available toattenuate the effect of heat stress on pigs, such as environmental solutions (water or feedingmanagement). However, these solutions are technically and economically difficult to implement. Thegenetic selection for improving environmental adaptation in pig production is the most promising longterm option. The PigHeaT project aims 1) at identifying QTLs for heat adaptation, by examining directresponses to find genes involved in metabolic ways, indirect responses to find genes affecting growthor robustness to environmental variations, 2) at better understanding the physiological mechanismsunderlying heat adaptation. It will provide tools for improving breeding strategies to face theupcoming global warming, and knowledge to better comprehend the physiological reactions ofanimals submitted to short and long term heat stress. The PigHeaT project is based on originalbiological resources and original experimental facilities. The studied population will be a backcrossbetween Large White pigs, productive but poorly thermotolerant breed, and Creole pigs, lowproductive but highly thermotolerant breed. The progeny issued from this backcross will express allpossible levels of thermal tolerance and production performances when submitted to heat stress,depending on the alleles received from their parents. High throughput phenotyping, metabolomics onall the progeny, and transcriptomics on a subset of extreme pigs selected on thermal toleranceresponse, will be applied. It will allow to refine the phenotypes and to achieve a high level of accuracyin QTL detection in the frame of the PigHeaT project. Additionally, the design will benefit from theunique combination of experimental facilities available at INRA: the first part of the project will relyon the backcross population raised in the experimental facilities located in the West Indies(Guadeloupe, tropical environment). The concomitant production of the same population in theexperimental facilities available in temperate France (Charente Maritime) will allow the detection ofgenetic by environment (GxE) effects for the QTL detected in Guadeloupe. Moreover, a heat wavephenomenon will be systematically simulated in the temperate environment at the end of the growingperiod. As a result, chromosomal regions robust or susceptible to GxE interactions will be identified,GxE being either tropical vs temperate, or tropical vs heat wave. Finally, an integrated analysis of the(fine) phenotypes and QTL will be proposed to better understand the metabolic pathways involved inheat stress responses. The respective use of the QTL and biological knowledge in further breedingstrategies will finally be considered.