Proceedings of the New Zealand Society of Animal Production.
1990, 50: 431-436
Proceedings of the New Zealand Society of Animal Production.
1990, 50: 431-436
Our basic technique involves holding a Day 5-6 embryo by negative pressure on a holding pipette and tearing the zona pellucida using 2 needles. A razor blade fragment is used to bisect the embryo and if required, a suction pipette manipulates demi-embryos into suitably prepared host zonae.
In a preliminary study bisected embryos were examined for development during 24-48 h culture. Bisection in Ca2+, Mg2+-free media had no effect on viability. Naked demi-embryos blastulated more readily than those which were zona-enclosed and later stages tended to be the most viable, with morulae showing particularly poor development. This was supported by transfer data, where 11% of bisected late morulae, 50% of early blastocysts and 74% of blastocysts resulted in lambs. In comparison, 40% of control (unbisected) embryos lambed. Transfer of zona-enclosed demi-embryos tended to yield more lambs per original embryo (67%) than naked demi-embryos (43%). When the technique was applied to early blastocysts and blastocysts during 3 exotic sheep multiplication programmes in 1988, 47% and 55%, 100% and 39%, 73% and 47% of bisected and control embryos resulted in lambs respectively. Survival to lambing of dehydrated late morulae, bisected and subsequently enclosed in zonae, was similar to untreated control embryos (73% VS 59%) and greater than for naked embryos (36%).
Our experiences indicate that bisected early blastocysts and blastocysts can increase the number of offspring in a MOET programme. However, since few blastocysts are available for bisection, and survival of demi- embryos is variable, we do not routinely use the technique.
Keywords: NZSAPAB; sheep; embryo; bisection; splitting; MOET
