A protocol used for splitting mouse embryos into two halves

8-16 cell embryos and early blastocysts were obtained from the oviducts and anterior portion of uterine horns of albino mice at 70 and 90 hr after LH injection respectively. Splitting of embryos was done by using two microtools attached to a micromanipulator unit (Research Instruments Ltd, UK). After bisection, each pair of the half embryos is transferred to a dish containing 2 ml of T-6 medium and cultured in CO2 incubator (at 39 degrees C, 95% RH and 5% CO2 in air mixture). Splitting of blastocysts as compared to 8-16 cell embryos was found difficult (35.48% vs 52.44%, respectively). 38.88% of bisected 8-16 cell embryos and 11.36% of bisected blastocysts developed on 48 hr culture. Information on splitting mouse embryos and their subsequent development in culture are significant in view of using the technique for commercial application and for research in developmental biology of animal embryos.