Estimates of variances due to direct and maternal effects for growth traits of Romanov sheep.

Records of growth traits of 2,086 Romanov lambs were used to estimate variance components for an animal model and genetic correlations between growth traits. Traits analyzed were birth weight (BWT), weaning weight (WW), 90-d weight (W90), and daily gain for the periods birth to weaning (DG1) and weaning to 90 d (DG2). Weaning was at approximately 40 d. Variance components were estimated using restricted maximum likelihood with an animal model including fixed effects for year x season, sex, rearing type, and litter size and random effects for the direct genetic effect of the animal (with relative variance h2), the maternal genetic effect (with relative variance m2), the permanent environmental effect (with relative variance c2), and random residual effect. Genetic correlations were estimated for a model with the same fixed effects and only additive genetic effects. Estimates of the variances of random effects, h2, m2, and c2, respectively, as a proportion of phenotypic variance were .04, .22, .10 (BWT); .34, .25, .0 (WW); .09, .01, .07 (W90); .26, .17, .02 (DG1); and .15, .01, .03 (DG2). Estimates of genetic correlations were .12 (BWT with WW); .24 (BWT with W90); .48 (WW with W90); .69 (DG1 with DG2); -.01 (BWT with DG1); .05 (BWT with DG2); .59 (WW with DG1); .47 (WW with DG2); .67 (W90 with DG1); and .98 (W90 with DG2). Results suggest that selection should be effective for WW, DG1, and DG2 but less effective for BWT and W90. An important maternal effect was observed for BWT, WW, and DG1. The estimates of genetic correlations showed no genetic antagonisms among the traits.