@conference {40246,
	title = {Animal industries in the 21st century - conclusions and challenges},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {50},
	year = {1990},
	month = {Jan},
	pages = {393-396},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Bisected embryos not only create identical twins, but can also   improve the efficiency of embryo transfer. We report here our   experiences in applying the technique to sheep MOET programmes.     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.    },
	issn = {1176-5283},
	author = {Wallace RD}
}
