Efecto de la GnRH administrada en la IATF a vaquillonas sin celo sobre el porcentaje de preñez

Abstract

We used 367 Angus heifers (15 months: 184, 18 months: 101 and 27 months: 81) to evaluate the effect of injected GnRH at TAI heifers showed no estrus on the pregnancy rate. On day 0, heifers received progesterone intravaginal device (IVD) plus estradiol benzoate. On day 8, IVD was removed and injected D-Cloprostenol and estradiol cypionate. Heifers were painted on the base of the tail and part of the rump. On day 10, heifers with ≥ 30 % rubbed off were considered to be in oestrus. In these moment, heifers not showing estrus were randomized to receive or not 0.105 mg Buserelin acetate (Painted+GnRH and Painted- GnRH, respectively). On this day was TAI, beginning estrous heifers (Group estrus). Pregnancy diagnosis was done at 39 days after TAI. Pregnancy rate was lower in heifers did not show estrus and no received GnRH (42.2%) compared to others groups (Painted + GnRH: 66.7% and estrous: 52.5%, P<0.05). In summary, heifers did not show estrus have lower pregnancy rate after TAI compared to heifers in estrous; these situation reverses with GnRH injection at TAI.