Taxa de prenhez em vacas mestiças submetidas ao protocolo de IATF e aplicação de análogo de GnRH 12 dias após a IA

This study aimed to evaluate the effect of GnRH administered 12 days after FTAI on pregnancy rate and progesterone levels in crossbred beef cows. Fifty-nine non-pregnant crossbred cows (Bos taurus indicus x Bos taurus taurus) previously selected by gynecologic examination with a body condition score (BCS) of 3.0 (scale of 1 - 5). Cows were randomly assigned to two treatments: TEB (n = 30), on day 0, an intravaginal progesterone releasing device (Primer®) was inserted and cows received i.m. 2.0 mg of estardiol benzoate (EB, Estrogin®); on day 8, the PRIMER was removed and cows received i.m. 300 IU of eCG (Novormon®) and 0.15 mg of PGF2α (Prolise®); on day 9, cows received i.m. 1 mg of EB. FTAI was carried out 48-56 hours after PRIMER removal; and TEBGnRH12 (n = 29): similar protocol to TEB, but with administration of 25 µg GnRH (Lecirelin, Gestran Plus®) on the 12th day after AI. On the 35th day after AI, diagnosis of pregnancy was performed by transrectal ultrasound. The pregnancy rate was analyzed by logistic regression. The results showed that 53.33% of the cows (16/30) in TEB and 37.93% (11/29) in TEBGnRH12 became pregnant after the first service. No significant difference was found among the pregnancy rate of animals in the treatments (P> 0.05). There was no difference between the P4 concentrations (TEB = 3.88 ng/mL and TEBGnRH12 = 3.12 ng/mL) among the heifers in the treatments (P> 0.05). The administration of GnRH analogs 12 days after TAI did not influence pregnancy rate or the progesterone concentration. Objetivou-se avaliar o efeito do GnRH, administrado 12 dias após IATF, sobre a taxa de prenhez e os níveis de progesterona sérica em vacas de corte mestiças. Foram utilizadas 59 fêmeas bovinas mestiças (Bos taurus indicus x Bos taurus taurus), não-gestantes, previamente selecionadas por exame ginecológico, com escore de condição corporal (ECC) 3,0 (escala de 1 – 5). Os animais foram alocados ao acaso, em dois tratamentos: TBE (n = 30) - no dia 0 inseriu-se o dispositivo intravaginal de progesterona (Primer®) mais 2,0 mg de BE (Estrogin®), im; no dia 8, retirou-se o PRIMER e aplicaram-se 300 UI de eCG (Novormon®) e 0,15 mg de PGF2α (Prolise®), im; no dia 9, aplicou-se 1 mg de BE, im, e realizou-se a IATF 48-56 horas após a retirada do PRIMER; e TBEGnRH12 (n = 29): o protocolo foi similar ao do TBE, porém com administração de 25 µg de GnRH (Gestran Plus®, Lecirelina) no dia 12 após a IA. No dia 35, após IA, foi feito o diagnóstico de gestação por exa