Synthesis of direct and maternal genetic components of economically important traits from beef breed-cross evaluations

Published information on relative performance of beef breed crosses was use d to derive combined estimates of purebred breed values for predominant tem perate beef breeds. The sources of information were largely from the United States, Canada, and New Zealand, although some European estimates were als o included. Emphasis was on maternal traits of potential economic importanc e to the suckler beef production system, but some postweaning traits were a lso considered. The estimates were taken from comparison studies undertaken in the 1970s, 1980s and 1990s, each with representative samples of beef br eeds used in temperate agriculture. Weighting factors for breed-cross estim ates were derived using the number of sires and offspring that contributed to that estimate. These weights were then used in a weighted multiple regre ssion analysis to obtain single purebred breed effects. Both direct additiv e and maternal additive genetic effects were estimated for preweaning trait s. Important genetic differences between the breeds were shown for many of the traits. Significant regression coefficients were estimated for the effe ct of mature weight on calving ease, both maternal and direct additive gene tic, survival to weaning direct, and birth weight direct. The breeds with g reater mature weight were found to have greater maternal genetic effects fo r calving ease but negative direct genetic effects on calving ease. A negat ive effect of mature weight on the direct genetic effect of survival to wea ning was observed. A cluster analysis was done using 17 breeds for which in formation existed on nine maternal traits. Regression was used to predict b reed-cross-specific heterosis using genetic distance. Only five traits, bir th weight, survival to weaning, cow fertility, and preweaning and postweani ng growth rate had enough breed-cross-specific heterosis estimates to devel op a prediction model. The breed biological values estimated provide a basi s to predict the biological value of crossbred suckler cows and their offsp ring.