Quantitative Trait Loci Identified for Body Temperature, Body Weight, Breast Yield, and Feed Digestibility in an Advanced Intercross Line of Chickens Under Heat Stress

Losses in poultry production due to heat stress have negative economic consequences. It has been previously demonstrated that host genetics partially determines response to heat in poultry. The F18 and F19 generations of a broiler (heat susceptible) by Fayoumi (heat resistant) advanced intercross line (AIL) were used to facilitate fine mapping of quantitative trait loci (QTL). Birds were exposed to daily heat cycles from 22 to 28 days of age, and phenotypes were measured in three major phases: pre-heat, first day of heat treatment, and one week of heat treatment. Cloacal temperatures were measured at all three phases; body weight at pre-heat and one-week heat phases. Breast muscle yield was calculated as a percentage of body weight, and Ileal feed digestibility was assayed from digesta collected from the ileum both at day 28. Birds were genotyped using the 600K Affymetrix chicken array and a genome wide association study was completed using Bayesian analyses and 1-Mb windows. Heritability estimates were low to moderate, ranging from 0.03-0.35. We identified QTL for: body temperature on GGA14, 15, 26, and 27; body weight on GGA1-8, 10, 14, and 21; feed digestibility on GGA19-21; and for breast muscle yield on GGA1, 15, and 22. A very large QTL for breast yield on GGA1 explained more than 24% of the genetic variation. Significant QTL were found for each of the measured traits, indicating the feasibility of using genomic selection to improve performance of animals raised under hot conditions. Support: USDA-NIFA-AFRI grant and Hatch project #5358.