Orsaker till kalvningssvårigheter och dödfödslar hos SLB och SRB

Abstract: Difficult calvings and stillborn calves are costly for the producer and lowering these frequencies can decrease the costs for the dairy operation. Each calving in the herd is registered by the farmer and stored in a central database. The information is used to monitor the level of calving-difficulties and stillborn calves in the herd and nationally. Monitoring of these registrations is important to detect possible changes. Breeding-value prediction for calving traits is based on the calving information in the database. Heritabilities of calving-traits are low and in the range of 0,01 to 0,08. Calvings are therefore largely affected by environmental factors such as age at first calving, season and herd. Indirect selection could be preferred instead of direct selection on certain traits that have low heritabilities or are difficult to measure. Rump angle and rump width are related to the size of the pelvic-opening, and have been suggested as predictors of calving performance. Heritabilities for rump angle and rump width varies between 0,25 and 0,45, which means a higher inheritance for these traits compared to calving-traits. In order to be good predictor-traits rump angle and rump width needs to be correlated with maternell calving ease. These correlation varies between -0,26 and 0,41, while the correlations to the direct effects varies between -0,06 to 0,33. Due to the wide range of correlations it is preferable to select directly for calving ease. The frequency of calving difficulty has been high for heifers of the SLB-breed. However, this is now decreasing. This decrease can have been obtained by genetic improvement of maternal calving ease. In Sweden, as well as abroad the frequency of stillborn calves is increasing. Further research is therefore needed in order to find ways to reduce this problem.