Postinsemination treatment of primiparous and multiparous cows with cloprostenol failed to affect ovulation and pregnancy rate in dairy cattle

Previous studies have demonstrated the facilitating effect of a single cloprostenol treatment postinsemination on ovulation and pregnancy rate in dairy cattle and Italian buffalos. This study was conducted to test the effects of 500 μg cloprostenol given intramuscularly immediately postinsemination to 55 primiparous and 60 multiparous Holstein cows (Bos taurus; TR) of a typical dairy operation in East Germany and to compare them with 57 primiparous and 48 multiparous saline-treated cows (CON). Animals of the TR and CON groups did not differ or only differed marginally for age at treatment, interval calving–treatment, lactation number, milk production on the day of treatment, body condition score, and their peri- and postparturient case histories. All animals were clinically and reproductively healthy on the day of treatment. They were inseminated once 12 h after the onset of estrus, scanned 24 h after insemination to confirm ovulation, and tested for pregnancy by transrectal palpation between Days 42 and 48 postinsemination. Treatment did not affect the number of cows ovulating. The overall combined pregnancy rate (PR) was 47.3%. Pregnancy rate did not differ statistically between TR and CON (46.1% vs. 48.6%; P > 0.05). In conclusion, this study failed to demonstrate beneficial effects of a postinsemination treatment of primiparous and multiparous cows with cloprostenol on ovulation and PR in a typical dairy cattle operation in East Germany.