Non-fertility in cows: influence of PGF, PMSG followed by PGF, progesterone and light.

An injection of PGF-2 alpha into cows at D + 10, D + 12, or at D + 14-15 showed several effects: regression of the corpus luteum in all cases 24 h after the injection, endometrium affected especially at D + 12, and initiation of formation of sorbitol when progesterone was present or of glucuronic acid when oestrogen occurred. Suitable parameters for selecting cows for superovulation, next to a rectal investigation, seem to be a biochemical investigation of cervical mucus on the occurrence of carbohydrates and of abnormal indole- and cholesterol-metabolites. In 'repeat breeders' several deviations were found: a delayed regression of the corpus luteum, a delayed atresia of follicles, a disturbed indole- and carbohydrate-metabolism and no conversion of DHA into oestrogen. Endogenous prostaglandins are apparently not sufficiently effective in a number of these cows and so treatment with PGF, eventually preceded by PMSG, and placing under a fluorescent lamp seemed to be beneficial in six out of eight 'repeat breeders'.