This research was conducted to know the effect of 125 mg of recombinant bovine somatotropin (bST) administered at weaning, on the productivity of sheep Pelibuey. 60 clinically healthy ewes with a body condition of 2.5 to 3 were used. The animals were divided into two groups, the treaty (30) and the control (30), at the same time both were subdivided into two groups, the flock that had one parturition (15), and with more than two (15). All females were synchronized under the same scheme of 12 days with an intravaginal sponge, 20 mg of medroxyprogesterone acetate (MPA), and support of 15 mg of PGF2a administered two days before the removal of the sponge. The bST was administered to the treated group the seventh day of synchronization, subcutaneously. Females were mating by the ram, after detection of estrus sinology. At 45 days the pregnancy diagnosis was performed by ultrasound and prolificacy was confirmed at the birth moment. It is concluded that under the conditions in which the experiment was performed bST showed no significant statistical effect in newly weaned females, but it showed minimal gains in the indicators of prolificacy and multiple births in animals treated with Somatotropin.