178 FIRST COMMERCIAL CATTLE IN VITRO EMBRYO PRODUCTION AND PREGNANCY RATES OF BOTH FRESH AND FROZEN IN VITRO EMBRYOS IN THE NORTH COAST OF PERU

Abstract

The objective of the study was to determine the pregnancy rate of fresh and frozen-thawed in vitro produced embryos transferred into recipients in the north coast of Peru. Artificial insemination results of frozen-thawed semen inseminated to cows in the same herd and season (summer) where the embryo transfers were performed was evaluated as control. For the in vitro embryo production, the rate obtained was 374 oocytes from 21 ovum pickup sessions (15.24 ± 8.91 oocytes/session). Of these oocytes, 246 were matured in bicarbonate buffered TCM-199 supplemented with 10% heat inactivated FCS as well as epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1), FSH, LH, oestradiol, and cysteamine for 24 h of incubation at 38.5°C, 5% CO₂, and 90% humidity. The oocytes selected post-maturation were fertilised with the frozen-thawed sperm that was subjected post-thawing to Percoll gradient (90 and 45% Percoll), centrifugated, and resuspended in a TALP-IVF medium supplemented with 20 μM D-penicillamine, 10 μM hypotaurine, and 1 μM epinephrine. The oocytes were then inseminated with a concentration of 1.5 million sperm mL^–1 in TALP IVF fertilization medium and incubated for 24 h at 38.5°C, 5% CO₂, and 90% humidity. Subsequently, the presumptive zygotes were transferred to medium of 50 μL drops of SOFaa supplemented with 5% heat-inactivated FCS which was later replaced by SOFaa and 1% heat-inactivated FCS on Day 5 after fertilization. The embryos were inspected and graded on Days 7 and 8 post-fertilization and incubation at 38.5°C, 5% CO₂ and 90% humidity. The blastocyst rate was evaluated on Day 7 post-fertilization. The blastocyst rate was 25.3% (21/83) and 4.19 ± 3.37 embryos per ovum pickup session were obtained. The embryo freezing media contained 1.5 M ethylene glycol as a cryo-protectant, and the method of thawing the embryo was the direct method (1 step). The pregnancy rate was compared by chi-squared analysis. The pregnancy rate for artificial insemination was 23.9% (1103/4612), and the pregnancy rate of fresh and frozen-thawed in in vitro embryos was 30% (13/43) and 20% (8/40), respectively (P > 0.05). Overall the pregnancy rates in the herd were relatively low, probably due the high environmental temperature during the season when the embryos were transferred and the semen was inseminated. Under those conditions, pregnancy rate was not affected by the use of fresh and frozen-thawed in vitro embryo transfer in comparison to the conventional artificial insemination of frozen semen in the coast north of Peru.