Demi-embryos were successfully produced by bisection of ICR mouse embryos at preimplantation stages. They were microsurgically bisected using a microsurgical blade attached to a micromanipulator after pretreatment with 0.5 % pronase in PBS for two minutes or not. Embryos with softened zona pellucida were more easily bisected and less damaged than intact embryos. The highest success rate in bisection has been achieved by selecting blastocysts (94.1 % in success rate with intact blastocysts and 100 % in success rate with zona softened blastocysts). Demi-embryos without zona pellucida were cultured in D-PBS or M-16 medium at 37deg C, 5 % CO2 in air for 72 hours for 2-cell stage embryos, 48 hours for 4-to 8-cell stage embryos, 24 hours for morula stage embryos and 6-12 hours for blastocyst stage embryos. For the in vitro culture of 2-cell stage embryos, 100 micro M 2Na-EDTA was added to the media. M-16 medium was better for the in vitro development of mouse embryos than PBS, and PBS is not considered to be suitable for long-term culture of embryos, especially at early stage of cleavage. In M-16 medium, developing rate of demi-embryos of which pair underwent development to form eublastocysts was 15.8 % at 2-cell stage, 16.8 % at 4-cell stage, 38 % at 8-cell stage, 89.6 % at morula stage and 94.4 % at blastocyst stage, respectively. The more rapid and efficient production of demi-embryos and higher viability after bisection can be expected by softening zona pellucida with pronase and by selecting morulae or blastocysts rather than embryos at early stage of cleavage.

Determination of the optimum parameters of cattle embryos production in vitro from high-producing cows after their slaughter on a meat-packing plant was realized in the conditions of the Republic of Belarus. Oocyte cumulus complexes of cows of black-motley breed and the conditions of their maturing were used as the object of experimental research. Oocyte cumulus complex were allocated with dissection of ovaries tissue placed into Hanks culture medium. The search and morphological estimation of quality of received oocyte cumulus complexes were realized by microscopic research. Then, the oocytes were placed into a culture medium for cell maturing in СО2-incubator at 38,5 deg C with the maximum humidity (98%), with presence of 5% СО2 under a layer of mineral oil for 24 hours. Matured oocytes were impregnated with the frozen-thawed sperm after capacitation. Oogenesis efficiency of production of pre-implantation germs in vitro was determined in accordance with the level of embryonic fission and production of viable germs. Use cumulus cells monolayer made it possible to increase the quantity of ripened oocytes on 5,2-5,7%, level of embryonic fission - on 14,0-14,6% and production of embryos - on 13,8-12,5% depending on a way of its production in comparison with groups of the cells which were cultivated without a monolayer. Thus, the research has shown the exploitability of use of cellular reproductive technologies in selection and breeding activities in cattle breeding. Their application in combination with embryo transplantation could make it possible to use the reproductive potential of high-priced oocyte donors more effectively for the genetic improvement of animal population efficiency