Heifers were treated with intra-vaginal pessaries impregnated with 200 mg SC-9880 (17α-acetoxy-9α-fluoro 11β-hydroxy-4-pregnene-3,20 dione). One or 2 days before removal of the pessaries (21 days after insertion) each heifer received a single intra-muscular injection of 750 i.u. pmsg.
Of the eighty-one treated heifers, sixty-six retained the pessaries for the prescribed period; fifty-five of these (83·3%) showed oestrus 24 to 72 hr after removal of the pessary. Of fifty-five heifers served or inseminated, twenty-four (43·7%) conceived. Of thirty-three heifers served at the second oestrous period, twenty-one (61·9%) conceived.
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