[Enhanced ovarian sensitivity to gonadotropins in anestrus in sheep]

Superovulatory doses of PMSG and hCG, injected to anestrus crossbred ewes, induced more intensive luteinization of large follicles and progesterone secretion in ewes, lambed by twins (9) at first pregnancy, then in the cases of singleton lambed ewes or nonlambing ones (12). The ovaries of 2 ewes, lambed by twins, have healthy follicles, with increased estradiol concentration in their follicular fluid despite the presence of ovulatory follicles, giving corpora lutea. It is concluded that enhanced ovarian reactivity at anestrus can be related to the reserves of the reproductive system in more prolific ewes.