Abstract
After an injection of 100μg of GnRH analogue, a functional corpus luteum was formed in a Holstein cow diagnosed as follicular cystic. The follicular cyst recurred, however, after the regression of the corpus luteum. To examine estrogen sensitivity in the hypothalamus of the cystic cow, 1 mg of estradiol-17β(E2) was injected, and LH concentration was determined. No LH surge was detectable in the cystic cow, although peak LH surge occurred 24 hours after E2 injection in 3 cows with normal estrous cycles. These results suggest that reduced sensitivity to estrogen in the hypothalamus is one cause of recurrent follicular cyst in this particular cow.
