Progesterone supplementation during the time of pregnancy recognition after artificial insemination improves conception rates in high-producing dairy cows.

This study examines the possible effects of progesterone (P4) supplementation during the time of pregnancy recognition, from Days 15 to 17 post-artificial insemination (AI), on reproductive performance in high-producing dairy cows. Cows in their 15th day post-AI were alternately assigned to a control, no-treatment group (C: n = 257) or treatment group (P4: n = 287) on a weekly rotational basis according to the chronologic order of their gynecologic visit. On the basis of the odds ratio, the interaction treatment × previous placenta retention had a significant effect (P = 0.