Deep-freezing of cow ‘half’ and ‘quarter’ embryos

Abstract

This paper describes a simplified method for biopsying goat embryos for sex determination, followed by the transfer of these embryos to recipient does. A 90° angle holding pipet is described, which permits holding the embryo in position and, with minimal effort, open the zona pellucida and excise 5–10 trophoblast cells with the aid of a microsurgical blade. Twenty-four embryos were biopsied, 12 of which were freshly collected (day 7) and 12 of which were cultured in vitro from collected morulae (day 6). In the course of the polymerase chain reaction (PCR) a 447 (male) and 445 bp (female) fragment of the DNA, derived from the trophoblast cells, was amplified. The primers used were specific for the highly conserved mammalian sequences of the ZFX and ZFY genes. Individual biopsied embryos were transferred to 24 synchronized recipient does. The pregnancy rate following transfer was 67% (8/12) in recipients receiving freshly collected blastocysts while only 8% (1/12) in the recipients receiving blastocysts cultured in vitro from morulae (P < 0.01). Four of the kids born were males and four females. The sex assigned to the embryos was correct in 83% of the cases.