Induction of ovulation in chronically hypophysectomized Booroola ewes

Abstract

Booroola Merino ewes, with (F+; N = 17) and without (++; N = 13) a copy of the fecundity gene were hypophysotectomized and 6 weeks later were given an i.m. injection of PMSG (high, medium or low dose) followed by hCG. The induced ovulation rates were observed laparoscopically. Ovulation rates were significantly higher (P < 0.01) in Booroola F+ ewes than in ++ ewes (8.00 ± 1.66 s.e.m. vs 3.62 ± 1.10 respectively). This suggests that the high fecundity of the Booroola ewe may be due primarily to ovarian rather than pituitary factors.