Sex determination in bisected bovine embryos and conception rate after the transfer of female demi-embryos

Abstract

The aim of this study was to evaluate the efficiency of sex determination after microsurgical splitting of D₇ (Day 7) bovine embryos and to test the conception rate after subsequent transfer of female demi-embryos. High-quality morulae (<I>n</I> = 100) and early blastocysts (<I>n</I> = 123) obtained from superovulated donors were microsurgically bisected and blastomeres biopsied from one half of bisected embryos were analysed by PCR using specific primers for the Y-chromosome determinant. The female demi-embryos were transferred (ET) in pairs (bilateral) or individually (ipsilateral) to synchronized recipients. Sex determination was successfully completed in 92% of morulae (42.4% female) and 89.4% of early blastocysts (43.6% female). Conception rates were 56.5% (30.4% identical twins) and 48.8% (19.5% identical twins) after bilateral (<I>n</I> = 46) and ipsilateral (<I>n</I> = 82) transfers, respectively. The number of foetuses in relation to the number of original embryos before splitting was 40/46 (87%) and 40/41 (97.6%) after bilateral and ipsilateral transfers of demi-embryos, respectively. The results document that the microsurgical bisection in combination with PCR sex analysis represents a rapid and reliable approach to increase an amount of sex-desired calves in embryo transfer programs.