Treatment of noncyclic lactating dairy cows with progesterone and estradiol or with progesterone, GnRH, prostaglandin F-2 alpha, and estradiol

The efficacy of two programs for treating noncyclic cows was compared. In t rial 1, 478 cows in five herds were randomly divided into two groups. Cows in one group (C group) were treated with an intravaginal progesterone devic e for 8 d followed in 48 h by 1 mg of estradiol benzoate to cows that had n ot been detected in estrus since device removal. Those in the other group ( CGP group) were treated with progesterone and estradiol as for the C group plus 10 mu g of a GnRH agonist (buserelin) at device insertion and 25 mg of PGF(2 alpha) 7 d after device insertion. In trial 2 with 729 cows in nine herds, the treatments were similar to those in trial 1 except that the dura tion of progesterone treatment was 7 d. No significant difference was found between trials and results from both trials were combined. Compared with C group cows, CGP group cows had a greater estrous response rate (93.2 vs. 8 9.1%), a greater conception rate to first artificial insemination (AI, 47.1 vs. 29.4%), marginally lower conception rate to second Al (52.9 vs. 59.7%) , lower nonpregnancy rate (8.3 vs. 11.1%). and shorter intervals from the s tart of breeding to conception by AI (9.8 vs. 15.3 d) or by AI or natural m ating (21.6 vs. 26.3 d). The treatment protocol used for the CGP group achi eved better reproductive performance than that used for the C group.