Strategies to reduce calf losses (stillbirths) by selection

Genetic variance is proven to exist in rates of stillbirth and calving difficulty since more than 30 years. First calvings are more strongly affected than later calvings. Earlier approaches in genetic evaluation and breeding strategies did not lead to the intended genetic progress. In Denmark. the Netherlands and Sweden increasing stillbirth rates are being observed in Holstein heifers, increasingly with normal or easy calvings. The heritabilities for the calving traits are low, but higher than in previous estimates. Nevertheless, the genetic valiance in stillbirth rate is large. In current Swedish studies the genetic parameters ale estimated separately for the direct and the maternal calving traits, because these traits al-e largely independent from each other. Accordingly. bulls have Co be evaluated both as sires and as maternal grand-sires of calves. Data collection is preferably carl-led out through official milk recording that is linked to an integrated cattle data bank. A model calculation on the most effective strategy for reducing calving difficulties and stillbirths resulted in the combination of a differentiated use of bulls on heifers or cows with ion-term selection for the maternal calving trait. Especially for bulls that are traded internationally. reliable bleeding values for the desired trails must be available.