Study on the appearance of the cavity in the corpus luteum of cows by using ultrasonic scanning.

A transrectal real-time B mode linear scanner was used to learn if the appearance of a cavity in the corpus luteum (CL) in cows causes infertility. Sixty-one cows that were confirmed to have ovulated after artificial insemination (AI) were used. Some of the cows that returned to estrus were examined two or three times; thus, a total of 78 observations were made. The rate of cavity appearance was 37.2% (29 78 ). In relation to the size of cavity, the rates of appearance were 30.8% of CL with cavities of 7 mm or greater and 24.4% with cavities of 10 mm or greater in diameter. It took more than 21 days for the cavity more than 10 mm to disappear. In the cows that were observed two or three times, the cavity did not tend to reappear. The mean period for return to estrus, mean serum progesterone concentration and mean pregnancy rate were not significantly different (P>0.05) for cows that had CL with or without a cavity. Our results suggest that the cavity mentioned above does not cause infertility.