Reproductive performance of dairy cows not detected in oestrus but with a detectable corpus luteum, in response to treatment with progesterone, oestradiol benzoate and prostaglandin F-2 alpha

Aim: To determine if the: reproductive performance of dairy cows not previo usly detected in oestrus but with a detectable corpus luteum before the pla nned start of mating (PSM), could be improved by treatment with progesteron e, oestradiol benzoate (ODB) and prostaglandin F-2 alpha (PGF). Methods: Cows in 18 herds which had not been detected in oestrus, but which had a detectable corpus luteum present at veterinary examination 7 days pr ior to the PSM (Day -7), were allocated to 1 of 2 groups. Treated cows (n=2 32) received an injection of 2 mg ODB and an intravaginal progesterone rele asing device (CIDR insert) on Day -7, and an injection of PGF on the day of insert removal 7 days later (Treated group). The Control group (n=243) rem ained untreated. Cows were mated to detected oestrus from Day 0, and concep tion dates confirmed by manual palpation or transrectal ultrasonography. Results: During the first 7 days of mating, 37.4% of Control cows and 65.9% of Treated cows were inseminated on detection of oestrus (p <0.001). Pregn ancy rates fur this period were 20.4% and 36.3%, respectively (p=0.001). Co nception rates to first insemination, pregnancy rates after 21 days of mati ng and at the end of the mating period were similar between groups (p >0.1) . Median interval from the PSM to conception did not differ between treatme nt groups (24 and 23 days for Control and Treated, respectively, p >0.1). Conclusion: Treating postpartum dairy cows which had not previously been de tected in oestrus but which had a detectable corpus luteum, with progestero ne, ODB and PGF did not significantly improve their reproductive performanc e compared with no hormonal intervention.