Figure 1.

Diagrammatic representation of protocols used to induce oestrus and ovulation in red deer hinds. Exogenous progestagen are delivered by intravaginal sponges impregnated with fluorogestone acetate (FGA) to inhibit endogenous secretion of luteinizing hormone (LH), allowing regression of dominant follicle by atresia. Small follicles present on the ovary at the end of progestagen treatment are stimulated by administration of Pregnant Mare Serum Gonadotrophin (PMSG). At removal (R) of intravaginal sponges, growth of follicle is sustained by endogenous release of gonadotrophins. A massive release of oestradiol from the dominant oestrogenic follicle then triggers oestrus and the LH preovulatory surge.