The failure of a prostaglandin F2 alpha analogue, cloprostenol, to initiate lactation in cattle.

An experiment was designed to determine if the analogue of prostaglandin F2 alpha, cloprostenol, at a dose sufficient to cause luteolysis, was lactogenic in cattle. The mammary glands of eight Friesian heifers were developed by treatment with progesterone plus oestrogen. Lactation was then initiated by administration of cloprostenol and subsequent milk production was compared to that of heifers lactating after a normal pregnancy. Injection of cloprostenol failed to initiate lactation. The level of prolactin but not cortisol in blood was substantially elevated following treatment. The results cast further doubt on the importance of prolactin in the lactogenic process but indicate the likely involvement of glucocorticoids.