Genetic parameter estimates for growth and fleece characteristics in Targhee sheep

Weaning weights at 60 (WW60) and 120 d (WW120), 60- to 120-d postweaning gains (PWG) for lambs weaned at 60 d, 120- to 365-d postweaning gains (YG) for lambs weaned at 120 d, fleece weights (FWT), and fiber diameters (FD) from 20 Targhee flocks were used to estimate parameters required for multiple-trait genetic evaluation. Flocks from western states (n = 10) recorded primarily WW60 (n = 1,762), WW120 (n = 5,961), YG (n = 2,388), FWT (n = 2,824), and FD (n = 2,000). Eastern flocks primarily recorded WW60 (n = 1,754) and PWG (n = 1,237). Heritability estimates were .01 for WW60 (.00 for western flocks and .07 for eastern flocks), .10 for WW120, .33 for PWG, .20 for YG, .41 for FWT, and .58 for FD. Additive maternal and maternal permanent environmental effects as a proportion of phenotypic variance were .10 and .09, respectively, for WW60 and .05 and .08 for WW120. In western flocks, maternal additive and permanent environmental effects on WW60 and WW120 were highly correlated (> .81), whereas WW120 and YG had a small positive additive genetic correlation (.19) but a negative residual correlation (-.34). Fleece weight had a genetic correlation of .50 with WW120 and YG. Supplemental analyses suggested that the observed genetic relationship between fleece weight and weaning weight arose primarily from a genetic association between additive direct genetic effects on fleece weight and additive maternal effects on weaning weight. Fiber diameter was nearly independent of body weights but had an undesirable additive correlation of .51 with FWT. In eastern flocks, WW60 and PWG had an additive correlation of .71 and a residual correlation of .15.