Serum free embryo culture medium improves in vitro survival of bovine blastocysts to vitrification

The aim of this study was to examine the effects of co-culture with Vero cells during the in vitro maturation (IVM) and three culture media, B2 + 5% fetal calf serum (FCS) on Vero cells, synthetic oviduct fluid (SOF) + 5% FCS, and SOF + 20 g L−1 bovine serum albumin (BSA), on the developmental competence of the embryos and their ability to survive vitrification/warming. We also tested the effect of morphological quality and the age of the embryo on its sensitivity to vitrification. The IVM system neither affects the embryo development up to Day 7 nor survival rates after vitrification. The culture of embryos in SOF + FCS and in Vero cells + B2 allowed obtaining more Day 6 and Day 7 blastocysts, and a higher % of Day 7 blastocysts vitrified than culture in SOF + BSA. Contrarily, on Day 8, more blastocysts were vitrified in SOF + BSA than in SOF + FCS. Blastocysts quality affected development after vitrification/warming, and Day 7 embryos showed higher survival rates than their Day 8 counterparts. Day 7 blastocysts produced in Vero cells or in SOF + BSA survived at higher rates than those produced in SOF + FCS at 24 and 48 h after warming. Embryo culture with BSA allows obtaining hatching rates after vitrification/warming higher than those obtained after co-culture with Vero cells in B2 and FCS. Moreover, this system provides hatching rates from Day 8 blastocysts comparable to those obtained on Day 7 in Vero cells. Further studies, including embryo transfer to recipients, are needed to clarify factors affecting the freezability of in vitro produced bovine embryos.