Gonadotropin releasing hormone treatment of dairy cows with ovarian cysts. I. Gross ovarian morphology and endocrinology.

Dairy cows diagnosed as having ovarian cysts were assigned to receive either sterile water or 100 mug GnRH (5 cows/group). Immediately prior to treatment and three days post-treatment, ovaries were observed via paralumbar laparotomy, photographed and visible structures and ovarian size recorded. Nine to thirteen days post-treatment, ovaries were removed. Blood plasma was collected for hormone determinations prior to each surgery, 1.5 and 3.0 hours and 1, 5 and 9 days post-treatment. Although concentrations were similar between groups prior to treatment, concentrations of progesterone were higher and LH and estradiol-17beta lower for GnRH treated cows than control cows, immediately prior to ovariectomy. A layer of luteal tissue approximately 5 mm thick was present around the periphery of the cystic structure at ovariectomy in 4 of 5 GnRH treated cows, but in only one control cow. The thickness of the luteal layer around the periphery of the ovarian cysts was correlated -.82, .78 and -.63 with estradiol-17beta, progesterone and LH, respectively. In summary, response to GnRH treatment in cows with ovarian cysts appears to be characterized in most cases by luteinization of the cystic structures.