Conception Rates and Calving Intervals After Prostaglandin F2α or Prebreeding Progesterone in Dairy Cows

Abstract

Two experiments were performed in two different herds to determine if utilizing prostaglandin F2α to induce estrus for first services would be effective in reducing the duration and variability of calving intervals. In Experiment 1, cows were assigned randomly as controls (n = 217) to be inseminated as they were detected in estrus (beginning d 42 to 53 postpartum depending on replicate) or treated with prostaglandin F2α (n = 185). In Experiment 2, the same treatments were utilized, except control cows (n = 124) were inseminated at their first detected estrus after d 40 postpartum, and treated cows received either one injection of prostaglandin F2α between d 54 and 63 (n = 116) or were given progesterone (via a progesterone-releasing intravaginal device) for 7 d, with the device removed 24 h after prostaglandin F2α (n = 116). More cows were inseminated and pregnancy rates were higher within 5 d after treatment with prostaglandin F2α and interval from prostaglandin F2α to first service was reduced compared with that of control cows. Duration and variation of calving intervals were unaffected in either experiment, despite the fact the elective waiting period was 6 to 23 d longer for treated cows than for controls. Prebreeding treatment with progesterone failed to improve conception rates, but the efficiency of estrous expression increased from 54% in prostaglandin F2α-treated cows to 71% in those cows also receiving prebreeding progesterone. We conclude that prostaglandin F2α was ineffective in improving reproductive performance of these herds undergood herd management. However, prostaglandin F2α offers the convenience of inseminating small groups of cows, controlling when breedings occur during the work week, and prolonging the elective waiting period without extending the calving interval. © 1989, American Dairy Science Association. All rights reserved.