The control of ovulation in the mare with reference to insemination with stored sperm

Abstract

1. In pony mares during oestrus in which a follicle was considered to be sufficiently ripe (thin walled) the intravenous injection of 500 i.u. pregnancy urine extract induced ovulation in nineteen out of twenty-three mares between 24 and 48 hr., in three cases within 24 hr., and in one case between the fourth and fifth days.2. Dialysed egg yolk as a medium for storage of horse sperm for 24 hr. was shown to give satisfactory results when ovulation is controlled by the above method, so that it occurs within 24 hr. after insemination. Nine single inseminations during one oestrus resulted in five pregnancies.3. The number of spermatozoa required for successful inseminations is discussed.4. Means of detecting a sufficiently ripe follicle before injection with pregnancy urine extract are described.5. It is shown that the duration of oestrus is shortened as the result of pregnancy urine injections.6. Data is given concerning the time which elapses between ovulation and the cessation of oestrus.