Development of Bovine Embryo Culture System for Maintaining Genetic Identity of Embryos

Abstract

Cumulus-oocyte complexes (COCs) recovered during an ovum pick-up (OPU) session from a cow is low (1 to 15 COCs). Moreover, mixing of two or more cows COCs to increase total number in a culture droplet will loss the genetic identity of embryos. The present study was aimed to develop a culture system suitable for culture of smaller number of COCs (less than 10 COCs). Slaughterhouse bovine ovaries were used for the experiment. Aspirated oocytes possessing an even cytoplasm and covered with minimum 3 layers of compact cumulus cell were subjected to in vitro maturation (IVM) followed by in vitro fertilization (IVF) using fresh semen capacitated by treating with heparin sodium salt. Cumulus cells were removed by gentle pipetting and denuded zygotes were subjected to in vitro culture (IVC) for blastocyst development. Cleavage rates were evaluated at day 3 (day 0:  day of IVF) and blastocyst rate at day 8 as a proportion of the presumed zygote transferred into IVC-I medium. Results show that development rate up to cleavage did not affect by COCs densities. Single COCs did not reach to the blastocyst stage when cultured individually. The development rate to the blastocyst stage was 13.9±9.0%, 10.8±4.9% and 16.6±3.9% for 3, 5, and 10 COCs  groups, respectively. The GPS group culture allowed the smaller numbers of COCs (1, 2, 3 and 4 COC per chamber) to develop at blastocyst stage. The present experiment developed in  vitro embryo production system for small number of bovine oocytes.