Abstract
The effect of confirmation of ovulation by rectal palpation and ultrasonography after artificial insemination (AI) on the development of the corpus luteum (CL) and conception rate was investigated in cows. A total of 90 clinically healthy Holstein-Friesian dairy cows were examined in this study. After AI, the cows were divided into three groups (30 cows per group). In Group I, ovulation was confirmed by rectal palpation at 24 h after AI. In Group II, ovulation was confirmed using transrectal ultrasonography 24 h after AI. In Group III, ovulation was not confirmed after AI. Day 0 was defined as the day when ovulation was confirmed in Groups I and II, and as the day after AI was performed in group III. Transrectal ultrasonography was performed on days 3, 5, 7, and 14 to measure the CL diameter, tissue area, and CL blood flow area, and the ratio of CL blood flow area to CL tissue area was calculated. On the day of CL measurement, blood samples were collected to determine the plasma concentrations of progesterone (P4) and estradiol-17β (E2). Pregnancy was diagnosed at 28 and 60 days after AI. A high conception rate of approximately 80% was achieved in Groups I and II, in which confirmation of ovulation was conducted. There were no differences in the diameter, tissue area, or blood flow area of the CL between the three groups. These results indicate that the confirmation of ovulation by rectal palpation and transrectal ultrasonography did not affect the formation and function of the CL or conception rate.