Investigation of morphological changes in bone marrow of young hens in the conditions of application of associated virus vaccines and sodium thiosulphate immunostimulant was realized in the Republic of Belarus. The associated virus vaccine was applied against infectious bursal disease, infectious bronchitis, infectious laryngotracheitis, and Newcastle disease. Research results showed that under the influence of inactivated vaccine against mentioned above diseases there was noted the increasing of quantity of granulocytic cells, there was stated an active hyperplasia of pseudoeosinophil cells. Immunization of young hens with the presented vaccine developed in the Institute of Experimental Veterinary Medicine of the National Academy of Sciences of Belarus promoted a short-term increasing of leucoerythroblastic index. Application of an alternative vaccine developed by Scientific and Production Enterprise Avivak did not render substantial influence on the morphology of bone marrow of chickens. Sodium thiosulphate applied in combination with associated vaccines (in 7% concentration in vaccine) caused the hyperplasia of lymphoid and thrombocyte cells, strengthened the proliferation and maturity of granular leukocytes

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

Investigation of the efficiency of ethylene glycol and sucrose application in the capacity of cryoprotectors for cryopreservation of cattle embryos and their thawing in the conditions of application of saline solutions (as their dissolution medium) and nutritive media with a various structure was realized in the conditions of the Republic of Belarus. Research results showed that application of ethylene glycol in concentration 1,5 M and sucrose in concentration 1,0M proved to be the most effective. Regardless of the applied media the average safety of embryos was 93,8-96%, and acceptability - 59,3-62,5%. Peculiar feature of ethylene glycol use as cryoprotector for preservation of cattle embryos was that it could be quickly absorbed by a cell and quickly deduced from it. It made it possible to realize embryo transfer immediately after thawing. Application of ethylene glycol and sucrose as cryoprotectors could considerably simplify the procedure of transplantation of the frozen-thawed embryos, practically reducing it to a procedure of artificial insemination

In the conditions of the Republic of Belarus there was realized a comparative study of meat productivity of mongrel Gereford х black-and-white heifers ad purebred black-and-white heifers in the conditions of different levels of concentrated feedstuff in cattle diets; and determine the most efficient and long-term method of animal breeding for meat. Research results showed that breeding of meaty of hybrids of Gereford х black-and-white heifers of the second generation without using the feeding concentrates in their diets or on using rations with a low rate of feeding concentrates (10-20%) proved to be more effective, than breeding of purebred black-and-white herdmates (for which specific density of the concentrated forages in diets made up 20% through pregnancy). Hybrids on Gereford breed in accordance with meat productivity level surpassed the purebred black-and-white animals. The most considerable results were marked at hybrid heifers with relative density of concentrates in a ration of 20% which in accordance with slaughter weight indexes surpassed the herdmates of black-and-white breed on 39,1 kg or on 23,68%, in accordance with slaughter yield - on 8,2%, in accordance with fresh carcass weight - on 37,9 kg or on 23,8%, in accordance with weight of inner porc - on 1,19 kg or on 20,62%.

Research of the peculiar features of correlation parameter of production indices of 870 mongrel inbred sheep with the various inbreeding coefficients was realized in the conditions of the Republic of Belarus. In course of study there was stated the one-sided influence of inbreeding on phenotypic indices of pair, individual and cumulative pair correlation genetic correlations of sheep productivity. The majority of them were the statistically authentic values with P less than 0,1 - 0,001. It was stated that coefficient variability of genetic correlation of wool productivity rendered influence on sheep inbreeding degree among which there were marked off animal units with inbreeding in degree of consanguinity with the coefficients of higher statistical confidence (with P less than 0,01 - 0,001) than animal units with degrees of close or low relationship and outbred animal units - (P less than 0,1 - 0,01). The majority of ewe productive quality correlation factors with a different inbreeding degree proved to be positive and authentic and could be used for an estimation of correlations between traits in selection process for population perfection