Random regression analysis of seasonal effects on reproductive genetics in the turkey (Meleagris gallopavo)

A random regression model was used to analyze egg production, fertility, and hatchability throughout the year in a male and female line of turkeys in a longitudinal nature. The genetic correlation between reproductive traits measured in each month was estimated by fitting third order orthogonal polynomials to sire effects. Correlations below 0.8 indicated that there was a genotype by environment (G×E) interaction. Heritability values, estimated for each month, showed similar trends in both the male and female lines. The heritability of egg production tended to increase in the second half of the year. In contrast, the heritabilities of fertility and hatchability were higher in the first half of the year. For all traits, the genetic correlations between months that were temporally closer were higher than the correlation between months that were further apart throughout the year. Correlations also tended to be higher for egg production than for fertility or hatchability. A reaction norm model was then used to analyze if reproduction genotypes respond differently to temperature and day length gradients. These environmental factors were variable throughout the year and may be producing the observed G×E interactions.