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Title: INFLUENCE OF DOMINANCE RELATIONSHIPS ON THE ESTIMATION OF DOMINANCE VARIANCE WITH SIRE-DAM SUBCLASS EFFECTS

Author
item GENGLER, N. - UNIV. OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd
item Macneil, Michael
item MISZTAL, I. - UNIV. OF GEORGIA-ATHENS
item PARIACOTE, F. - UNIN. OF NEBRASKA-LINCOLN

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The most important genetic effects for selection are called additive effects. Dominance effects cannot be selected for, but if important should be accounted for in prediction of additive genetic values or in planning optimum matings for a single generation. Results of analyses of two data sets of Herefords from the USDA Livestock and Range Research Laboratory suggest that dominance effects may account for up to 25% of variation in birth and weaning weights. The standard errors, however, are large. Further, the analyses suggest that consideration of all dominance relation- ships rather than only those from full sibs (same sire and dam) may result in different estimates of the importance of dominance genetic effects. If true, that result suggests that national cattle evaluations would also be affected by the kinds of dominance relationships used when dominance effects are included in the statistical model.

Technical Abstract: Two data sets from USDA Livestock and Range Research Laboratory were analyzed to study the influence of dominance relationships on estimates of dominance variance. The first consisted of 4,155 birth weight (3,884 weaning weight) records of inbred USDA Line 1 Herefords. The second set consisted of 8,065 birth weights (7,380 weaning weights) from a line-cross experiment with five lines. Two models were used. Both included fixed effects of year-sex of calf and age of dam, and covariates for calving date and inbreeding of animal and dam. For second data set, additional covariates were line composition and heterozygosity coefficients. Random effects were direct and maternal genetic, maternal permanent environment, sire-dam subclass and residual. Model 1 considered sire-dam subclasses unrelated. Model 2 related sire-dam subclasses with parental dominance relationship matrix. Variance components were estimated using REML. For first data set estimates with Model 2 of relative genetic direct and maternal variances, direct-maternal correlation, permanent environment and dominance variances for birth weight were: .35, .13, -.02, .03 and .25, respectively, and .39, .11, .04, .06 and .14 for second data set. For weaning weight, estimates were .20, .15, -.37, .19 and .11, respectively, for first data set and .16, .20, -.07, .18 and .18 for the second data set. Differences between estimates with Model 1 and 2 were unimportant except for dominance variance which may be due to increased information from family relationships other than full-sibs. The assumption of unrelated sire-dam subclasses might not be appropriate for estimation of dominance variance in populations with additional dominance relationships.