Data on 8890 calves for 200 day weight and 5890 calves for 400 day weight for the Simmental cattle obtained from the Meat and Livestock Commission in Britain were used to estimate variance components and heritabilities. There were 2259 sires and 2720 head-year-season represented in the 200 day weight data. Corresponding figures for 400 day weight were 1910 and 2116. Variance components and heritabilities were estimated usind Restricted Maximum Likelihood fitting an animal model. Data were subdivided into 3 populations for computational convenience. Heritability estimates for both traits were about 0.31 in model fitting only additive genetic effects. Including direct maternal effect resulted in a decrease of 41 and 13 percent in heritability estimate for additive genetic effects in 200 and 400 days weight respectively. Materal effects accounted for 7 percent of total variance in 200 day weight and was not important in 400 days weight. Models fitting direct effects and permanent environmental effects fitted better with similar estimates of direct genetic variances and permanent environmental variances accounting for 8% of variation in 2 00 day weight and 5% in 400 day weight. Fitting direct, maternal and permanent effects gave similar estimates for direct and permanent variances with maternal variances close to zero. Estimates of genetic covariances between direct and maternal effects were close to zero.

R. A Mrode, R. Thompson

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XV. Beef cattle, sheep and pig genetics and breeding, fibre, fur and meat quality., , 271–274, 1990
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