Plasma FSH, LH, the positive feedback of oestrogen, ovulation and luteal function in the ewe given bromocriptine to suppress prolactin during seasonal anoestrus

Abstract

Treatment of 16 Scottish Blackface ewes with 1 mg bromocriptine, i.m. twice daily for 12 days, reduced prolactin concentrations in peripheral plasma from 64 .+-. 10 ng/ml before treatment to < 4 ng/ml. This treatment had no effect on the proportion of ewes discharging luteinizing hormone and follicle stimulating hormone in response to 12.5 .mu. estradiol benzoate (3/8 before compared with 5/16 during treatment) or the proportion of ewes ovulating in response to estrogen treatment. Plasma progesterone concentrations remained low even in ovulating ewes. Treatment with bromocriptine alone is unlikely to restore estrous cycles to ewes in seasonal anestrus.