Effects Of Thermal Conditioning Of Embryos and Heat Stress Of Chicks On Physiological Responses Of Diverse Chicken Genetic Lines

Heat stress negatively impacts animal welfare and productivity. Understanding the genomics of resistance to heat stress will facilitate selection for populations with improved welfare and productivity in hot environments. We therefore initiated a major research project to elucidate the genomics of heat resistance in poultry.  Nearly 2,000 chickens were studied in experimental designs that allow investigation of effects of breed, thermal conditioning of embryos, cyclical heat exposure of chicks, and interaction of heat stress with response to inflammatory agents. To facilitate fine mapping of QTL, a highly advanced intercross line was included and genotyping done with a chicken 650K SNP chip. DNA from diverse breeds (broiler and Fayoumi) were sequenced. Egg thermal conditioning had a significant effect on body weight at all weeks post-hatch and on the change in body temperature before and after one week of chronic, cyclic heat exposure. Analyses of live-bird blood biomarkers demonstrated significant effects of egg thermal conditioning and chick heat stress on the difference of several blood biomarkers between pre-heat and chronic heat exposure measures. The biological model of heat stress and the feasibility of identifying genetic markers controlling important heat-response traits in poultry were validated with these initial data. The extensive physiologic phenotypes and biological samples are serving as the foundation of continued studies to elucidate the genes, networks and epigenetics of control of heat stress in poultry.