Reliability of cyst diagnosis and effect of energy status on LH released by estradiol or GnRH in cows with ovarian cysts

Abstract

The purpose of this study was 1) to test the efficacy of on-farm milk progesterone analysis kits to diagnose different types of ovarian cysts and 2) to examine whether or not the failure of estradiol-induced LH release in cows with ovarian cysts was correlated with energy status, as reflected by plasma 3-beta-hydroxybutyrate (BHB) concentrations. A total of 82 cows (36 to 155 days after calving) were presented to 13 experienced cattle veterinarians for diagnosis of ovarian cysts as either follicular or luteal on the basis of medical history, palpation per rectum of the ovaries and on-farm EIA milk progesterone analysis. In 77% of cases, the milk progesterone values concurred with results of the radioimmunoassay (RIA) plasma samples. Two trials were conducted: In Trial 1, 16 and 20 follicular and luteal cysts respectively, were correctly diagnosed. Of these, 8 follicular and 10 luteal cysts responded with an LH surge: one or both blood samples collected at 18 and 24 hours after 1 mg estradiol benzoate contained LH > 10.0 ng/ml. The plasma concentration of BHB in all cows in Trial 1 ranged from 0.20 to 4.73 mmol/l (12% were >0.8 mmol/l, although none of the cows exhibited clinical signs of ketosis). There was no correlation between LH response to estradiol and BHB concentration. In Trial 2, there were no differences in the LH response of cows (n = 40) 15 minutes after the administration of one of three commercially available preparations of gonadotrophin releasing hormone (GnRH); this LH response to GnRH was the same in normal cows and in cows with cysts. None of the cows in Trial 2 had BHB concentrations indicative of ketosis (>0.8 mmol/l). In conclusion, the use of on-farm milk progesterone kits did not appear to improve the diagnosis rates of cysts, and it was not possible to explain the failure of cows with cystic ovaries to respond to estradiol on the basis of nutritional imbalance as reflected by elevated BHB concentrations.