No abstract

The objectives of this experiment were to evaluate effect of age of the conceptus at death on subsequent interval to estrus and to determine whether prostaglandin F2 alpha (PGF) treatment after induced conceptus death would reduce interval to estrus. Sixty-four beef cows were diagnosed pregnant by ultrasonography between 24 and 50 d of gestation. Nine pregnancy groups were identified; each encompassed a 3-d interval from d 24 through 50 of gestation. Cows were allocated at random within pregnancy group to be treated with colchicine to induce conceptus death. Forty-eight hours after colchicine treatment, conceptus death was verified by ultrasonography and each animal received either saline or PGF. There was no evidence of an effect of age of conceptus at death on the subsequent interval to estrus after either saline or PGF. Interval to estrus after saline was 13.5 +/- .8 d, which was greater (P less than .01) than the 6.2 +/- .8 d after PGF. After saline, the estimate for the linear effect of time on serum progesterone (P4) was -1.32 +/- .36 ng/d and was less (P less than .05) than -2.83 +/- .36 ng/d for cows given PGF. Cows were exposed to fertile bulls at the first postabortion estrus. Pregnancy rates were 37.5% for cows given saline vs 31.3% for those given PGF. These results indicate that interval to estrus after conceptus death between 24 and 50 d of gestation is not affected by the age of the conceptus and can be reduced by PGF treatment.