Gestation with in vitro produced embryos from oocytes of ovariectomized cows

Abstract

The objectives of this work were to evaluate the efficiency of in vitroproduction (IVP) of embryos from ovariectomized cows and the pregnancy rate of transferred frozen-thawed embryos. One hundred and twenty Argentine-Holland cows were ovariectomized in 6 sessions by using the effeminator by vaginal via. The ovaries were transported at 18-22°C into saline solution supplemented with antibiotics during 6 h and processed whitin of 11 h since the first ovary obtained. Cumulus-oocytes complexes (COCs) were aspirated from small antral follicles (2-8 mm in diameter). The COCs were matured in TCM 199 plus 10% oestrus cow serum for 22 h. Following maturation the oocytes were fertilised with frozen-thawed semen in TALP medium and cultured in CR1aa medium. At Day 7 and 8 after fertilisation, good quality blastocysts and expanded blastocysts were equilibrated in 1.5 M ethylene glycol. Two embryos were loaded into 0.25 ml straws and frozen. The embryos were thawed and directly transferred into the recipients. A total 57 dairy heifer was used as recipients. Pregnancy diagnosis was performed by rectal palpation 55 d after embryo transfer.

The efficiency of IVP technology was 9.5 oocytes and 2.7 embryos per ovary. The overall pregnancy rate was 31.5%. A higher pregnancy rate (P<0.05) was obtained for Day-7 (35.5%) versus Day-8 (16.6%) IVF embryos. It can be concluded from the results that a culled cow could produce 0.82 additional pregnancy after application of this technology. These data demonstrate that IVP embryos originating from ovaries of ovariectomized cows is a good alternative to preserve genetic resources and for commercial purposes.