Mixed model procedure for the unification of within herd evaluations through national beef sire evaluation
A mixed model is developed for the unification of beef cattle within herd evaluations and national beef sire evaluation. The model accounts for both sire and dam effects and is used to obtain predictors of individual animal genetic merit for traits of economic importance. The prime purpose of the unification is to provide a link between herds in order that best linear unbiased predictors of expected progeny differences (EPDs) can be determined for yearling bulls and heifers which are comparable across herds. The methodology is extended to include predicting sire material EPDs for weaning weight, within herd dam direct and maternal EPDs for weaning weight, and development of within herd phenotypic, genetic, and environmental management trend lines;The method of unification is to build within herd mixed model evaluation equations for herd dams, contemporary groups, and sires on a herd by herd basis. Dams and contemporary group equations are absorbed into sire equations for each herd. After absorption, the sire equations are consolidated from all herds to form a set of national sire evaluation equations. Best linear unbiased predictors are determined for the sires and used in back solving for within herd contemporary group estimates and dam predictors. Young animal EPDs for traits of interest are computed as a function of parent EPDs plus their own performance.