Changes of estrogens in milk of thoroughbred mares during foal estrus.
Levels of three kinds of estrogens, estrone, estradiol-17β and estriol, in milk from 5 Thoroughbred mares during foal estrus were measured by radioimmunoassay. Estradiol-17β and estriol levels in milk have no relevant importance in predicting con-ceptionable estrus. Only estrone concentration in milk showed a relation to the con-ceptionable estrus cycle in thoroughbred mares. This is probably the first report that deals with estrone concentration in milk during foal estrus and the measurement of estrone could be a reliable guide to know the estrus to be capable of conception in postpartum mares.