Endocrine profiles in cows with ovarian cysts experimentally induced by treatment with exogenous estradiol or adrenocorticotropic hormone

• Published in: Theriogenology Vol. 28; no. 6; pp. 871 - 889
• Main Authors: Refsal, K.R., Jarrin-Maldonado, J.H., Nachreiner, R.F.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.12.1987
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/0093-691X(87)90038-0

The objectives of this study were to 1) induce formation of ovarian cysts in dairy cows and identify accompanying changes in luteinizing hormone (LH) and ovarian steroids and 2) characterize profiles of gonadotropin and sex steroid secretion in cows with experimentally induced ovarian cysts. Nonlactating dairy cows, synchronized to be in late diestrus, received either a placebo, 10 mg estradiol-17β, or multiple treatments of 100 IU adrenocortropic hormone (ACTH) gel. Jugular blood was drawn every 4 h for 8 d and palpation per rectum performed daily for 20 d. Ovarian cysts formed in 0 of 5 control, 2 of 5 estradiol-treated, and 2 of 5 ACTH-treated cows. Estradiol treatment resulted in synchronous luteal regression with a preovulatory surge-like release of LH occurring before luteal regression was complete. At 5 to 8 d after administration of estradiol, cows were either identified as having an ovarian cyst or had a spontaneous preovulatory LH surge that was followed by ovulation. Preovulatory surges of LH did not occur after luteal regression in ACTH-treated cows, with ovarian cysts detected within 2 to 3 d. There was great variation in basal endocrine profiles in cows with experimentally induced cysts. After administration of exogenous estradiol (1 mg), only one of four cows with induced cysts responded with a preovulatory surge-like release of gonadotropins.