Studies on Fertility Traits in Swedish Dairy Cattle

Abstract

Fertility records from 57,057 heifers and 55,422 cows of the Swedish Red and White breed (SRB) and Swedish Friesian cattle (SLB) were submitted to analysis. Herd fertility level was the most important source of variation for female fertility, accounting for some 8-25% of the total variance. Age did not affect heifer results but had a significant effect on cow results. The most important external factors affecting female fertility are herd and season. Adjusting for these factors seems necessary if bull evaluation on female fertility is to be performed on the data. The influence of the other environmental factors seems to be of little importance under Swedish conditions.