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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #139381
Title: ESTIMATES OF GENETIC PARAMETERS AND GENETIC CHANGE FOR REPRODUCTION, WEIGHT, AND WOOL CHARACTERISTICS OF TARGHEE SHEEP

Author
item Hanford, Kathryn
item Van Vleck, Lloyd
item Snowder, Gary

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2002
Publication Date: 3/1/2003
Citation: Hanford, K.J., Van Vleck, L.D., Snowder, G.D. 2003. Estimates of genetic parameters and genetic change for reproduction, weight, and wool characteristics of Targhee sheep. Journal of Animal Science. 81:630-640.

Interpretive Summary: Genetic parameters from both single-trait and two-trait analyses for litter size at birth (LB, n=38,625), litter size at weaning (LW, n=38,625), birth weight (BW, n=33,994), weaning weight (WW, n=32,715), fleece weight (FW, n=36,807), fleece grade (FG, n=36,807), and staple length (SL, n=3,341) were estimated for Targhee sheep from data collected from 1950 to 1998 at the U.S. Sheep Experiment Station, Dubois, ID. Breeding values (BV) from both single-trait and 7-trait analyses were compared with respect to genetic trends. Estimated changes in BV over time did not differ substantially for single-trait and 7-trait analyses, except for traits highly correlated with another trait that was responding to selection. Estimated BV averaged by year of birth for the prolificacy and weight traits increased over time, but were unchanged for the wool traits. LW and WW are both components of litter weight weaned, an economically important trait, but are lowly heritable. However, selection based on litter weight weaned over a long period can result in a moderate positive response in both LW and WW in a flock of dual-purpose breed, such as the Targhee. Although, LB and BW are lowly heritable, positive genetic correlations between these traits and litter weight weaned suggest that selecting for litter weight weaned would result in positive genetic gains in both LB and BW. Wool traits, which have moderate to high heritability, should not be adversely affected over a long period of selection for litter weight weaned, due to near zero genetic correlations between litter weight weaned and wool traits. These results are in agreement with a similar study of Columbia sheep.

Technical Abstract: Genetic parameters from both single-trait and bivariate analyses for litter size at birth (LB, n=38,625), litter size at weaning (LW), n=38,625), birth weight (BW, n=33,994), weaning weight (WW, n=32,715), fleece weight (FW, n=36,807), fleece grade (FG, n=36,807) and staple length (SL, n=3,341)were estimated using REML with animal models for Targhee sheep from data collected from 1950 to 1998 at the U.S. Sheep Experiment Station, Dubois, ID. Estimated breeding values (BV) from both single-trait and 7-trait analyses were compared with respect to genetic trends. Direct heritability estimates from single-trait analyses were 0.10 for LB, 0.07 for LW, 0.25 for BW, 0.22 for WW, 0.54 for FW, 0.41 for FG, and 0.65 for SL. Estimate of direct genetic correlation between LB and LW was 0.77 and between BW and WW was 0.52. Estimate of genetic correlation between FW and SL was positive (0.54), but negative between FW and FG (-0.47) and between SL and FG (-0.69). BW was lowly correlated with both LB and LW and WW was small and positively correlated with both LB and LW. FW and SL were lowly correlated with both LB and LW. FG was lowly and positively correlated with both LB and LW. Estimates of correlations between FW and both BW and WW were positive and low to moderate. Estimates of correlations between weight traits and FG and SL were small. BV averaged by year of birth from both the single-trait and multiple-trait analyses for the prolificacy and weight traits increased over time, while mostly unchanged for the wool traits. Estimated changes in BV over time did not differ substantially for single-trait and multiple-trait analysis, except for traits highly correlated with another trait that was responding to selection.