Dissertation - Open Access
Doctor of Philosophy (PhD)
Monte Carlo simulation techniques were used to assess the merits of three methods for calculation of the genetic correlation when traits have been measured on half-sibs of each sex. The restricted maximum likelihood, path coefficient and covariance component estimators did not differ significantly in their accuracy. Path coefficient and covariance component methodologies gave nearly unbiased estimators for traits of high heritability. Across both levels of heritability, the restricted maximum likelihood methodology resulted in genetic correlations being estimated with significantly smaller sampling variance than the other methods. Genetic correlations were estimated for age of puberty, weight at puberty, conceptions per service, gestation length, calving difficulty, progeny birth weight, progeny preweaning daily gain and mature weight measured on females, with postweaning daily gain, carcass weight, fat trim weight, and retail product weight measured on male half-sibs. Correlations of the female traits with postweaning daily gain, carcass weight, and retail product weight generally were similar to each other. Correlations of fat trim weigh with the female traits were similar in magnitude and opposite in sign to the correlations of postweaning daily gain, carcass weight, and retail product weight with the female traits. Predicted correlated responses to one phenotypic standard deviation of selection for increased postweaning daily gain were increased age at puberty 3.39 days, weight at puberty 1.02 kg, dam’s progeny birth weight .50 kg and mature weight 1.45 kg and reduced g station length .20 days and the frequency of calving difficulty .07 percent. The estimated genetic correlations of postweaning daily gain of the dam’s steer half-sibs with conceptions per service and dam’s progeny preweaning daily gain had absolute values greater than one and were positive and negative, respectively. Predicted correlated responses to one phenotypic standard deviation of selection for reduced fat trim weight at a constant age were increased age at puberty 7.22 days, weight at puberty 5.29 kg, gestation length .17 days, the frequency of calving difficulty .05 percent, birth weight, .12 kg and mature weight .22 kg and decreased conceptions per service .01 units. The estimated genetic correlation of age constant fat trim weigh with dam’s progeny preweaning daily gain was less than negative one.
Library of Congress Subject Headings
Beef cattle -- Genetics
Monte Carlo method
South Dakota State University
MacNeil, Michael D., "Genetic Correlations Among Sex-Limited Traits" (1982). Electronic Theses and Dissertations. 5819.