An attempt to induce multiple ovulations in beef cows by unilateral ovariectomy and HCG administration.

This experiment was designed to test the following two hypotheses: (1) beef cows unilaterally ovariectomized will ovulate more viable ova at the first post-operative estrus than intact animals when all are given human chorionic gonadotropin (HCG) at estrus, and that (2) this result is more likely if the CL-containing ovary is not removed. Thirty-five Angus and Anguscross cows were assigned randomly to the following treatment groups: (1) sham operation, (2) enucleation of the CL, (3) removal of the Cl-containing ovary, (4) removal of the non-CL-containing ovary, and (5) removal of the non-CL-containing ovary and enucleation of the CL. Surgery was performed on day 13 or 14 of the estrous cycle (estrus -day 0). All cows were injected intravenously with 2,500 IU HCG at the onset of the first postoperative estrus and inseminated 12 hr later. The treatments neither caused superovulation nor interfered with fertility. The interval from treatment to estrus was shortened (P<.01) by CL removal. (