|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2002
Publication Date: 3/1/2002
Citation: Sawalha, R., Keown, J.F., Snowder, G.D., Van Vleck, L.D. 2002. Genetic parameters for subjective milk score and litter weight for Targhee, Columbia, Rambouillet, and Polypay sheep [abstract]. Journal of Animal Science 80(Suppl. 2):43.
Interpretive Summary: No interpretive summary is required.
Technical Abstract: Genetic parameters for subjective milk score (MS) and litter weight at 70 days (LW) were estimated independently by breed. Data collected from 1990 to 2000 at the U. S. Sheep Experiment Station were analyzed with an animal model using REML. Number of records was 13,900 for 5,807 ewes. Records were grouped according to parity as: first, second, third and greater, and all records. Single and two trait analyses resulted in similar genetic parameter estimates within a trait. Estimates of heritability for MS by parity ranged from 0.05 to 0.18 for first, 0.01 to 0.27 for second, 0.05 for Targhee and 0.10 for the other breeds for mature MS and from 0.08 to 0.13 for all records. Milk score at first and second parities was highly correlated genetically; estimates ranged from 0.74 to 1.00. Similarly, MS at first and second parities were highly genetically correlated with mature MS. Consequently, additive genetic milking ability at maturity could be evaluated as early as first parity. Heritability estimates for LW ranged from 0.00 to 0.18 for all breeds and parity groupings. Genetic correlation estimates at first parity between MS and LW were high (1.00) for Rambouillet and Polypay; moderate for Targhee (0.27) but near zero for Columbia (-0.02). At second parity, estimates were more variable and ranged from -1.00 to 1.00. For mature records, estimates ranged from -0.28 to 0.84. For all records, estimates were positive and moderate for all breeds (0.15 to 0.68). Estimates of genetic correlation between LW at first or second parity with mature LW were mostly high and positive except for Targhee (-0.10) and Polypay (0.14) at first parity. Litter weight for mature ewes could be improved by selection at first or second parity.