In the conditions of the Republic of Belarus there were analyzed indices of impregnating ability and efficiency of stud bull mothers of various genotypes on a kappa-casein gene (CSN3). As a result of genotyping of kappa-casein gene by DNA-diagnostics method it is revealed three genotypes - CSN3АА, CSN3AB, CSN3BB. Frequency of occurrence of homozygous genotype CSN3AA at stud bulls - 87,3%; heterozygotic CSN3AB - 20,5%; homozygous CSN3BB - 1,2%. Statistically authentic difference between these indices depending on a genotype it is not established. Thus, authentic connection between indices of impregnating ability and efficiency of stud bull mothers and their genotype on a locus of a kappa-casein gene that specifies in absence of influence of the last on the given indices is not established and gives the chance to conduct selection on gene CSN3 without decrease in breeding value of stud bulls on reproductive qualities.

In the conditions of the Republic of Belarus there was realized a complex evaluation of producer bulls of different genotypes of origin for the further correction and breeding in different categories of agricultural enterprises. In course of the study there was conducted a preliminary (without quality evaluation of daughters) estimation of bulls which gave a precise performance of each bull, made it possible to correct its type and direction of breeding. Research made it possible to considerably increase the genetic trend in accordance with indexes of milk productivity which would make it possible to form a regional type of black-and-white cattle with the given indexes of productivity and reproduction. In course of the study there were analyzed the following breeds: black-and-white, Holstein, Hungarian breeding, Swedish breeding. Comparative evaluation of reproductive qualities of bulls in accordance with age-specific and breed types was presented. Body conformations of bulls of Holsten and Black-and-white of different ae-specific groups were stated. Results of complex evaluation of full-grown, under 5 year-old and replacement producing bulls of Holstein and Black-and-white breeds were presented.

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

Research of the reproductive qualities of sows of different genotypes depending on duration of gestation period was realized in the conditions of an industrial pig complex of the Republic of Belarus. In course of research there were analysed 500 sows and 1991 farrowings and was stated that only 61,4% sows had gestation period in the range of physiological standards (at the average -11,5 days). In 17,8% of sows the mentioned above parameter was on 1,6 days shorter and in 1/5 of all sows under investigation it was 0,6 days longer. A higher productive performance was marked in double-breed sows of a genotype (White Large x Belarusian Meaty) with the average gestation period of 114,2 days. There were no essential deviations marked in the duration of the gestation period depending on the ordinal number of farrowing, though for the third farrowing the duration of the gestation period made 114,8 days and was 0,2-0,4 days longer as compared with the first and the second farrowings

Evaluation of amino-acid, mineral, and vitamin content, as well as indexes of meat safety obtained from young stock of cattle of different genotypes in accordance with possibility of its application as raw material for baby food production was realized in the conditions of the Republic of Belarus. In course of study there were used bull calves of white-and-black breed, Limousin breed and their crossbreeds. Research results showed that young stock of Limousin breed, Limousin x white-and-black crossbreds, and white-and-black breed (control group) gave high quality meat. In meat of animals of experimental groups there was stated high quality of almost all nonessential amino acids and nonreplaceable amino acids, in meat of crossbreeds there was noted considerable increasing of polyunsaturated fatty acids. In it there was 12,31% of linoleic acid against 4,75 in Limousin breed and 2,77% in white-and-black breed; and eicosatetraenoic acid – 2,4% against 1,24% and 0,7%, respectively. Also in meat of experimental bull calves there was stated higher content of vitamins, calcium and phosphorus, while the content of cuprum and zinc decreased

As a result of the realized in the conditions of the Republic of Belarus research on revealing the influence of polymorphism character and the influence of presence of various allelomorphic variants of IGF-2 gene in breeding boars genotype on fattening and carcass traits of stores of Belarusian large white and Belarusian meat breeds it was established: 1. frequency of occurrence of desired QQ genotype among boars of the Belarusian meat breed was rather low and has made 10%. Among boars of the Belarus large white breed the given genotype has not been revealed. Heterozygotic genotype Qq had a rather wide range - from 26,6% at boars of the Belarusian meat breed to 43,2% at boars of the Belarusian large white breed; 2. fattening boars of both studied breeds which had been received from the boars bearing in their genome Qq genotypes of IGF-2gene showed the tendency for predominance in fattening and carcass traits over their herdmates which had been received from the boars bearing in their genome qq genotypes; 3. The posterity of boars of the Belarusian meat breed bearing in their genome the homozygous QQ genotype, authentically surpassed in fattening and carcass traits their analogues which had been obtained from fathers with a genotype qq. The following traits were higher: age of achievement of body weight; daily average weight gain in case of fattening; feed expenses per unit of live weight gain; slaughter yield; weight of a back third of half carcass. Research results showed, that IGF2gene (a gene of the insulin-like growth factor) could be a perspective candidate gene which makes it possible to predict the growing capacity and carcass trait of pigs of Belarusian breeds. Taking into consideration the influence undesired q allele, for the increasing of fattening and carcass traits of pigs it was possible to recommend the realization of estimation of replacement boar pigs using the data analysis of their genotype of IGF2 gene, as additional criterion of their selection

For the first time in the Republic of Belarus there were developed the effective methods of marker-dependent selections directed towards increasing the performance traits and preventive measures of pig diseases of the Belarusian Large White breeds. Application of the presented techniques in practice made it possible to increase the multiple fetation of sows on 0,5-1,5 piglets, increase livability of stores on 1,1-5,7%, increase the average daily weight gain on 17g, lower feed expenses on 0,04 FU. In course of the realized studies there was studied the polymorphism of Ryr-1, ESR, E.Coli (ECR F 18) FUT 1 and IGF-2 genes, there was developed the efficient methods of marker-dependent selection. Research results showed that application of methods of molecular gene diagnostics proved to be economically feasible. In the conditions of rather low expenses for testing of boars and sows there was stated the considerable increases in economic efficiency of pork production. Creation of reserve populations with a desired genotype breed will make it possible to accelerate the breed-forming process

In the research the genetic structure of populations of bulls Vitebsk of cattle breeding state farm and cows of Belarusian Black-and-White breed of Joint-Stock Company Olgovskij of Vitebsk region (Republic of Belarus) on a locus of a gene of kappa-casein was analyzed. As a result of genotyping a gene of kappa-casein by DNA-diagnostics method there were revealed three genotypes CSN3**AA, CSN3**AB, CSN3**BB. Frequency of occurrence of homozygous genotype CSN3**AA at cows has made 69,5%, at bulls of Vitebsk cattle breeding state farm - 78,3%; heterozygotic genotype CSN3**AB - 26,3% and 20,5%; homozygous genotype CSN3**BB - 4,2% and 1,2%, respectively. Frequency of CSN3**A allele in population of cows and bulls has made 0,83 and 0,88; CSN3**B - 0,17 and 0,11%, respectively. The presence of authentic influence of polymorphic variants of a gene of kappa-casein on level of milk yield and fat and protein content in cow milk was stated. The highest milk productivity in course of 305 days of lactation was observed at cows with homozygous genotype CSN3**BB (5984 kg), that was on 890 kg higher than in animals with genotype CSN3**AB (5094 kg), and on 1406 kg higher (Р less than 0,05), than at animals with CSN3**AA genotype (4578 kg). Cows with B kappa-casein allele in genome were characterized by higher fat content in milk (CSN3**AB - 3,61%, CSN3**BB - 3,72%) than animals with a CSN3**AA genotype - 3,60%. Cows with genotype CSN3**BB had higher level of protein in milk (3,28%) in comparison with the animals with CSN3**AA genotype (3,18%). In animals with CSN3**AB genotype the mentioned above index 3,19%. Research results showed that genetic variants of the gene of kappa-casein are important for selection practice as they could be used as breeding-genetic markers which could raise milk yields and protein content in milk

In the conditions of the Republic of Belarus there were analyzed high productive traits of meaty calves and cross breeds bred in accordance with a system cow-calf, as well as the possibilities of using veal meat obtained in ecologically safe areas for infant food production. At the age of 6,5-7 months the weight of fresh carcass of bull-calves of sharolez breed in comparison with aberdin-angus х black-motley herdmates was on 41,6 kg (Р less than 0,001) higher, carcass yield and slaughter yield – on 13,8% (Р less than 0,001) and 13,6% (Р less than 0,001), respectively. The fat content in sharolez meat was 4,9% against 8,9%; protein - 21,9% against 18,8%. The black-motley suckling bull-calves surpassed their herdmates which were grown up by technology of dairy cattle breeding at the age of 6-6,5 months according to indexes of weight of fresh carcass - on 16,3 kg or 21,7% (Р less than 0,01); according to indexes in a slaughter yield - on 16,6% (Р less than 0,001); and according to indexes meat flesh in a carcass - on 1,5%. According to quality indexes, amino acid structure, acceptable concentration of toxic elements content, pesticides, antibiotics, radionuclides and other harmful substances the veal meat of calves which were bred on a system a cow-calve in ecologically pure zones proved to be important meat raw materials to produce infant food products.

In the conditions of the Republic of Belarus there was analyzed the interrelation between the main indexes of cattle milk performance of dairy cattle of Large Red Belarusian breed and Belarusian Black-and-White breed with different genotypes of kappa casein gene. In course of the study there was determined the frequency of occurrence of genotypes and alleles by kappa-casein gene in population of cows of mentioned above breeds. Values of correlation coefficients between some indexes of milk performance of the studied breeds were analyzed. Correlation factors between the basic indexes of milk performance of cows with different genotypes of kappa casein. Research results showed that milk protein content and butter-fat yielding capacity were in negative association with the main breeding trait of dairy cattle – amount of milk yield. Butter-fat yielding capacity and milk protein content correlated positively. Thus, selection breeding in accordance with one of this traits will promote increasing of the other. Besides, it is necessary to realize DNA-diagnostics of cattle according to kappa casein gene and to select animals having in their genomes allele CSN3**B connected with higher milk protein content.