86 Awardee Talk: Improving climatic resilience in pigs through genomics: From trait definition and genetic modeling to biological validation

Breeding programs have substantially improved productive and reproductive efficiency in worldwide swine populations. However, increased performance is often accompanied by reduced climatic resilience due to greater metabolic heat production. Genomic selection is an effective tool for alleviating the negative effects of heat stress, but it requires traits that effectively capture the physiological, behavioral, and morphological mechanisms regulating the heat stress response. In this presentation we will first describe the genetic background of heat tolerance based on routinely recorded phenotypes and climatic variables obtained from public-weather-station databases. There are clear genotype-by-environment interactions across environmental conditions and the definition of the critical periods for quantifying the environmental gradient directly impacts the accuracy of genomic prediction of breeding values for heat tolerance. Secondly, we will describe the genetic background of various behavioral, physiological, and morphological indicators of heat stress in maternal line pigs, including automatically recorded vaginal temperature, skin temperature measured in different body locations and times of the day, respiration rate, panting score, body condition score, hair cortisol, hair density, and ear area. We will also present recently developed indicators of climatic resilience based on variability metrics of longitudinal measurements of automatically recorded body temperature in lactating sows. These traits are heritable and can be successfully included in genomic breeding programs. Furthermore, we will discuss the transgenerational effects of heat stress in maternal-line pigs from quantitative and molecular perspectives, including an epigenomic analyses of in utero heat stress that identified over 200 genomic regions that are differentially methylated in in utero heat stressed pigs and provide results from a comprehensive biological validation study based on in-depth phenotyping of genetically divergent animals. We will also discuss key challenges and opportunities for breeding for improved climatic resilience in pigs. In summary, we will: 1) provide a comprehensive description of the environmental-gradient variables and critical periods fitted in genomic evaluations of heat tolerance; 2) describe the genetic background of various indicators of heat tolerance and climatic resilience; 3) present the accuracies of genomic predictions for each indicator trait; 5) describe key results from biological validation studies; and, 6) make recommendations for the implementation of genomic selection for improved heat tolerance in pigs.