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Gestation with in vitro produced embryos from oocytes of ovariectomized cows

Abstract:

The objectives of this work were to evaluate the efficiency of in vitro production (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 CRIaa 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 (16.67%) 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.