J. Anim Sci.
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J. Anim Sci. 1980. 50:653-663.
© 1980 American Society of Animal Science
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Estimation of Additive and Nonadditive Direct and Maternal Genetic Effects from Crossbreeding Beef Cattle1

E. U. Dillard, Oswaldo Rodriguez2 and O. W. Robison

North Carolina State University, Raleigh 276503

Abstract

Data from straightbred and crossbred cattle involving Angus, Charolais and Hereford breeds were analyzed to obtain fitted constants for each of 22 breed groups and to estimate breed additive, heterotic, breed maternal and average maternal heterosis effects for birth weight, preweaning average daily gain, weaning weight and type score. Year, sex, age of dam and age of calf at weaning, as well as the interaction herd x year, were significant sources of variation for all traits. Among breed groups, crossbred calves showed higher values than the straightbred Angus and Hereford calves for each trait studied. Charolais additive effects, expressed as a deviation from Hereford, were positive (P<.05) for birth weight, average daily gain and weaning weight. Angus additive effects for birth weight were negative (P<.01). Charolais maternal contributions to preweaning traits exceeded those of Hereford and Angus. Angus maternal effects significantly exceeded Hereford for all traits except type score. Nonadditive genetic effects were significant for daily gain, weaning weight and type score. Equations for predicting the performance of all breed groups studied and some other combinations of interest were calculated with the partial regression coefficients for each trait and the additive, heterozygotic, maternal and average maternal heterosis coefficients for each breed group. Estimates of heterosis from the predicted least-squares means were: birth weight (2.4%), daily gain (3.8%), weaning weight (3.9%) and type score (3.7%). Comparisons of the breed group model to the regression model that estimated breed additive and heterozygotic (intra-locus interaction) direct and maternal effects suggested that specific maternal heterosis, epistasis and (or) linkage may have contributed to differences among breed groups for weaning weight and average daily gain. However, these additional effects accounted for only about 1% of the variance. Thus, it appears that the regression model adequately explains the variation in the data.

Footnotes

1 Paper No. 5945 of the Journal Series of the North Carolina Agr. Res. Service, Raleigh.

2 Present address; Universidad Centro Occidental, Barquisimeto, Lara, Venezuela.

3 Dept. of Anim. Sci.






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Copyright © 1980 by the American Society of Animal Science.