Genetic parameters among weight, prolificacy, and wool traits of Columbia,Polypay, Rambouillet, and Targhee sheep

Genetic parameters for Columbia, Polypay, Rambouillet, and Targhee sheep we re estimated using REML with animal models for prolificacy, weight, and woo l traits. All bivariate analyses included a covariance between additive gen etic effects for the two traits plus appropriate additional covariances. Nu mber of observations by breed ranged from 5,140 to 7,095 for prolificacy tr aits, from 7,750 to 9,530 for weight traits, and from 4,603 to 34,746 for w ool traits. Heritability estimates ranged from .03 to .11 for prolificacy t raits (litter size at birth and litter size at weaning), from .09 to .26 fo r weight traits (birth weight and average daily gain), and from .25 to .53 for wool traits (fleece weight, fleece grade and staple length). Estimates of direct genetic correlations among prolificacy and among weight traits we re positive and ranged from .58 to 1.00 and .18 to 1.00, respectively. Esti mates of direct genetic correlation between fleece weight and staple length were positive (.50 to .70) but were negative between fleece weight and fle ece grade (-.60 to -.34) and between staple length and fleece grade (-.72 a nd -.40). Prolificacy and wool traits were essentially uncorrelated. Weight and prolificacy traits were slightly positively correlated. Weight traits had a moderate positive direct genetic correlation with fleece weight and s taple length, but were uncorrelated with fleece grade. These estimates of g enetic parameters between prolificacy, weight, and wool traits can be used to construct multiple-trait selection indexes for dual-purpose sheep.