Suplementação com progesterona após inseminação artificial em tempo fixo em vacas nelores

Abstract

The aim of the study was to evaluate the effect of progesterone supplementation (P4) after the artificial insemination at fixed time (IATF), on the area of the corpus luteum (CL), gestation rate and precocious embryo loss of cows. Forty cows were randomly distributed in two experimental groups (G), with G1 (control group) (n=20) - without supplementation with P4 and G2 (treated group) (n=20): with P4supplementation from second to seventh day after IATF. All cows received on day zero (D0) the intravaginal device containing 1g of P4, together with application of 3mg of estradiol benzoate. In D8, 150mg of prostaglandin F2α and 200IU of equine chorionic gonadotrophin were injected intramuscularly (IM). In D9, after 24 hours of withdrawal of the device, 1mg of gonadotrophin releasing hormone was administered IM, as an inducer of ovulation. Animals were submitted to IATF 52 hours after removal of the P4 device. At 7 days and 14 days after IATF, the CL area was evaluated. The diagnosis of gestation was made 30 and 60 days after IATF, to determine the pregnancy rate and early embryo loss. For the quantitative variables that presented normal distribution, ANOVA at 5% of significance was performed. For the variables that did not present normal behavior, the Kruskal-Wallis test was used. For the qualitative binominal variable (gestation rate) using the chi-square. There was no difference in ovulation rate between treatments, with a mean of 80% in the control group and 90% in the supplemented group. For the luteal body area there was no difference between groups, the mean area in D7 was 2.2±0.69cm2 and 2.0±0.85cm2 and in D14 of 1.8±0.79cm2 and 1.6±0.49cm2, respectively, for the control and treated groups. There was no difference for pregnancy rate of D30 and D60, with rates of 5% (Control) and 0% (Treated), in both evaluations. There was no embryonic loss in the period evaluated. Intravaginal supplementation with slow release of P4 in cows from the second to the seventh day after IATF did not provide better reproductive indexes.