Estimates of genetic parameters and genetic change for prolificacy, weight and wool characteristics of Columbia, Targhee and Polypay sheep

Genetic parameters for prolificacy, weight and wool traits were estimated using REML with animal models for Columbia and Targhee sheep from data collected from 1950 to 1998 and for Polypay sheep from data collected from 1977 to 1998 at the U.S. Sheep Experiment Station, Dubois, ID. Direct heritability estimates ranged from .09 to .11 for litter size at birth (LB), .02 to .07 for litter size at weaning (LW), .05 to .10 for litter weight weaned (LWW), .17 to .27 for birth weight (BW), .16 to .22 for weaning weight (WW), .53 to .68 for fleece weight (FW), .30 to .41 for fleece grade (FG) and .55 to .76 for staple length (SL). Estimates of direct genetic correlations between pairs of prolificacy traits ranged from .19 to .94. Between BW and WW estimates of direct correlations ranged from .52 to .57. Estimates of genetic correlations between FW and SL were positive (.55 to .65) but were negative between FW and FG (−.47 to −.37) and between SL and FG (−30 to −.69). Estimates of correlations were positive but small between BW and prolificacy traits and moderate and positive between WW and prolificacy traits. FW was lowly and negatively correlated with both litter size traits, but was lowly and positively correlated with LWW. FG was lowly to moderately and positively correlated with all prolificacy traits, while SL was lowly to moderately and negatively correlated. Estimates of correlations between weight traits and FW were lowly to moderately and positively correlated. Estimates of correlations between weight traits and FG were lowly and negatively correlated. SL was positively correlated with BW. Correlations between SL and WW were small (−.04 to .08). Estimates of breeding value for WW increased the most over time for all three breeds, while LB, LW, LWW, BW, WW, FG and SL also increased. Estimates of breeding value for FW increased for Columbia and Polypay and decreased for Targhee