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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #90674
Title: HETEROSIS AND INBREEDING DEPRESSION

Author
item Macneil, Michael
item PARIACOTE, F - UNEFM, VENEZUELA
item Van Vleck, Lloyd

Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Other
Publication Acceptance Date: 8/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: 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, & 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 & 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 & .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.

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, & 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 & 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 & .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.