Differences between organic dairy cows sired by artificial insemination and natural service

This study investigated differences between phenotypes of daughters of artificial insemination (AI)-bulls and daughters of natural service (NS)- bulls, respectively, on organic dairy farms in Switzerland. Organic rules recommend the use of natural mating. Therefore it is of interest whether those two groups of phenotypes show different characteristics on organic farms. Only farms using both AI and NS with sires of the same dairy breed as the inseminated cows were included in the study. First lactations of 594 cows from 29 farms were analysed. Dairy cows descending from NSbulls showed lower somatic cell scores (SCS), a tendency to shorter calving intervals (CI), and a tendency to lower daily milk yields (DMY) compared to cows descending from AI-bulls. No effects of service method on other analysed health parameters were found. Around 70% of NS-bulls and 26% of AI-bulls had been bred in the same regions as their daughters. 1.8% of AI-bulls and 30.8% of NS-bulls had been bred on an organic farm. One explanation for the effects found in cows descending from NS-bulls might lie in their better adaptation to local conditions. However, effects of the service method and the bull’s environment of origin cannot be distinguished and it cannot be excluded that the chosen NS-bulls incidentally had higher genetic merits for CI and SCS than AI-bulls.