Endocrinological and histopathological aspects of the infertility in the ewe caused by oetrogenic clover

Abstract

The possible causes of infertility induced by potent estrogenic clover were studied in 50 permanently infertile ewes. Progesterone concentrations were normal throughout the cycle in 7 of 12 animals studied; the remainder showed either high or low concentrations. Histologic examination of these animals did not reveal any consistent changes in the H/E sections of the pituitary glands or evidence of hyperplastic changes in the adrenal cortex. In the cervix cycstic changes were much more severe than in the uterine horns and squamous metaplasia was observed in 1 animal. Luteinizing hormone (LH) concentrations were assessed in 6 animals after a single injection of 40 mcg estradiol-17beta (E2) 1 week after the animals were spayed. 5 of the ewes exhibited the rapid release of LH in response to E2 that is found in the normal spayed ewe. The results show that the infertility caused by clover is related to morphological changes that occur primarily in the cervix. It is also possible that estrogenic clover creates imb alances in the luteolytic system.