283 INFLUENCE OF THE MOMENT OF EMBRYO TRANSFER IN PREGNANCY RATES IN FEMALE BOVINE INSEMINATED WITH IVP EMBRYOS OFTHE NELLORE BREED

Abstract

The in vitro production (IVP) of bovine embryos is a biotechnique that has created new perspectives in animal reproduction and improvement. However, one of the main issues in the diffusion of this technology concerns the rate of pregnancy of the recipient cows. The objective was to verify the relationship between the fertilization in vitro, the day the recipient female was in estrus, and the pregnancy rates. Two hundred sixty crossbred recipient cows were selected from July to November 2008, synchronized with 2 different protocols at a random moment of the estrous cycle. One of the groups (G1) composed of 110 females that received 2.0 mL of D-cloprostenol, i.m. in only dose. The other group (G2), with 150 females, received a norgestomet auricular implant and 2.0 mg of estradiol benzoate i.m. On the fifth day, the females received, i.m. 200 IU of equine serum gonadotrophin and 150 μg of D-cloprostenol. The implant was removed on the eighth day, and 24 h later all animals received 1.0 mg of estradiol benzoate. The recipients entered in estrus 1 day before, 1 day after, and on the day of IVF. The embryos were transferred on Day 7 after fertilization, trancervically in the ipsilateral uterine horn that contained corpus luteum. The gestation diagnosis was made by ultrasound scan 30 days after the transfer. Data were analyzed using SAS software (version 9.0, SAS Institute, Cary, NC, USA). Initially, data were analyzed by normality test using Proc Univariate; however, a normal distribution was not observed. Data were then analyzed by PROC FREQ with nonparametric method of chi-square test and a significance level of 5%. Among the recipients, 40 were observed in estrus 1 day before IVF (D - 1), 137 on the IVF day (D0) and 83 were observed in estrus 1 day after (D + 1), resulting in a total rate of pregnancy of 38.8%. For each day the resulting pregnancy rates were 42.50% in D - 1, 41.61% in D - 0, and 30.12% in D + 1. These results suggest that there is no relationship between the day of the recipient’s estrus, the day of IVF, and pregnancy rates. There was no influence of the day of estrus in relation to the day of IVF in the gestation rates of the recipients of IVP embryos. However, more studies concerning the recipients are necessary, because they assume an important role in the success of the IVP. The authors thank Brio Genetic and Technology.