Estimation of genetic parameters for production traits of corn and dual-purpose sheep

Phenotypic data were obtained for eight production traits from matings of seven unique sets of four fully inbred lines of each of two different heterotic groups of corn. Estimates of variance components due to line effects were obtained with derivative-free restricted maximum likelihood. Comparisons of estimates of variance due to line effects with and without taking relationships into account indicated that when relationships among lines are ignored, potential estimates of variance are less than when relationships are considered. When multiple covariates for marker alleles were included in the model, estimates of variance due to line effects increased for most traits when marker alleles were included in the analysis in contrast to what was expected. Genetic parameters for Columbia, Polypay, Rambouillet and Targee sheep were estimated using REML with animal models for fertility, growth and wool traits, and litter weight weaned. Heritability estimates ranged from.03 to.11 for fertility traits, from.07 to.26 for growth traits and from.25 to.53 for wool traits. Heritability estimates ranged from.02 to.12 for litter weight weaned. Estimates of direct genetic correlation among fertility traits and among growth traits were positive and ranged from.58 to 1.00 and.18 to 1.00, respectively. Estimates of direct genetic correlation between fleece weight and staple length were positive (.50 to.70), but were negative between fleece weight and fleece grade ($-$.60 to $-$.34) and between staple length and fleece grade ($-$.72 to $-$.40). Fertility and wool traits were essentially uncorrelated. Growth and fertility traits were slightly positively correlated. Growth traits had a moderate positive direct genetic correlation with fleece weight and staple length, but were not correlated with fleece grade. Litter weight weaned had a moderate positive genetic correlation with fertility and growth traits, but was not correlated with wool traits. Genetic parameters can be used in deriving economic indexes for selection of dual purpose sheep