Artificial Induction of Lactation in Ewes: The Role of Prolactin

Abstract

The mammary glands of 30 non-pregnant, intact ewes were developed by subcutaneously injecting oestrogen plus progesterone at intervals of 3 days from day 0 to day 27. Two days later (day 29), 15 ewes were injected subcutaneously with 18 mg ergocryptine, to inhibit specifically secretion of prolactin. Then groups of ewes, each comprising five ergocryptine-treated and five untreated ewes, were injected from days 30 to 34 with either four intravenous injections each day of 1 i.u. syntocinon, one subcutaneous injection each day of 10 mg dexamethasone trimethylacetate, or two subcutaneous injections each day of 2· 5 mg oestradiol benzoate plus 6·25 mg progesterone. All ewes were milked by hand on days 30-50. Within 24 h of injecting ergocryptine, levels of prolactin in serum were reduced to negligible values ( < 2 ng/ml).