Effects of the administration of oxytocin or carbetocin to dairy cows at parturition on their subsequent fertility.

A total of 501 dairy cows were allocated sequentially to be treated immediately after parturition with either 25 iu oxytocin or 35 mg carbetocin, or to be left untreated. Any abnormal parturition, including assisted calving, the birth of twins or dead calves, retained fetal membranes or hypocalcaemia, was recorded, and the cows were examined between 28 and 42 days after calving for endometritis. Pregnancy was diagnosed from 30 days after insemination. The incidence of endometritis was similar (14 per cent, 16 per cent and 19 per cent) and the median intervals from calving to pregnancy were similar (118, 121 and 119 days) for the cows treated with oxytocin, carbetocin or receiving no treatment, respectively. The incidence of endometritis and the median intervals from calving to pregnancy were also similar between the groups for the cows that had an abnormal parturition.