Effect of eCG on in vitro embryo production in beef cattle in the dry tropics

Abstract

The effect of equine chorionic gonadotropin (eCG) was evaluated on follicular development and oocyte morphology through follicular aspiration (OPU) and its relationship with In Vitro production of embryo in beef cows. Nine Bos taurus and Bos indicus cows were used, cows were 3 to 7 years old, with an average weight of 700 (±120 kg) kg, these cows were subjected to OPU according to the experimental protocol. The cows were kept in buffel grass (Cenchrus Cilaris sp.) with mineral and food supplementation. The cows were divided in 4 groups, with an structural nested design, 3 different breeds x 4 eCG dosages (0 Ul, 1000 Ul, 2000 Ul and 3000Ul), with 3 repetitions per dosage. The ovarian cycle was synchronized with an intravaginal device (CIDR-B®, 1.9 g) and 0.7 ml estradiol benzoate, during 7 days, plus corresponding dosage of eCG, followed by OPU at CIDR withdrawal. After every OPU session, the oocytes were washed and was evaluated and incubated with In Vitro maturation media (MIV) in an Eve incubator, at 38.5ºC and 5% of CO2. After the MIV incubation, oocytes were placed in fertilization media (FIV) and fertilized; 18 hours post-fertilization, plates were placed in embryo incubation media (CIV) and incubated for a further 48 hours and the the media was changed and incubated for a further 96 hours. At this time, blastocyst rate was estimated. There were significant effects of breed (P<0.05), however, eCG dose did not affect oocyte quality nor blastocyst rate.