N. Gengler et al., ESTIMATION OF THE DOMINANCE VARIANCE FOR POSTWEANING GAIN IN THE US LIMOUSIN POPULATION, Journal of animal science, 76(10), 1998, pp. 2515-2520
The objective of this study was to estimate the dominance variance for
postweaning gain in Limousin cattle. Data included 215,326 records of
postweaning gain from 205 to 365 d, provided by the North American Li
mousin Foundation. Parental dominance subclasses were formed and relat
ed using the method of Hoeschele and VanRaden. Variance components wer
e estimated using Method R based on six samples of 50%. Fixed effects
in the model included contemporary group apd covariates for inbreeding
and breed composition (percentage Limousin). Heterozygosity was negat
ively correlated with breed composition (< -.99) and was therefore not
included in the model. Two types of contemporary groups used as origi
nal groups from the National Cattle Evaluation were partially based on
breed composition. Original contemporary groups that were too homogen
eous for breed composition were replaced by herd-year-sex classes. Two
models were used with the two data sets. Model 1 contained the fixed
effects described above and an additive genetic effect. Model 2 Includ
ed a dominance effect in addition to the effects contained in Model 1.
In total, four combinations of contemporary group x model were used.
Dominance variance was computed as being four times the estimated pare
ntal subclass variance. Estimates for inbreeding depression and breed
composition (percentage Limousin) were all small and not greatly affec
ted by inclusion of dominance effects or changes in contemporary group
s. Estimates of the additive variance (expressed as percentage of the
phenotypic variance) were only slightly affected, with values between
20 and 21%. Dominance estimates were highly affected when passing from
original (10%) and to alternative contemporary groups (18%). Such lar
ge values may indicate that dominance is important for postweaning gai
n. Results showed the advantage of an individual dominance approach ba
sed on sire-dam combinations; therefore, expected gains through the us
e of specific combination ability as a part of the mating selection cr
iteria for growth might be high.