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.

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

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.

Determination of influence of polymorphic variants of genes of kappa casein, beta-lactoglodulin and alpha-lactoalbumin on indexes of milk producing ability (milk yield, fat and protein content) of brood cows of Belarusian white-and-black breed was studied in the conditions of the Republic of Belarus. In course of analysis of polymorphism of kappa casein gene there was revealed the exceeding of frequency index of allel CSN3**a over the index of allel CSN3**b (0,795 and 0,205 respectively). Studying of polymorphism of beta-lactoglodulin gene showed that the frequency indexes of allel variants formed in the following way: BLG**a - 0,489 and BLG**b - 0,511. There were revealed three genotype variants of alpha-lactoalbumin among which the highest frequency indexes were stated for heterozygous genotype LALBA**aa *(32%) and LALBA**bb (14%). There was calculated the genetic equilibrium for loci of studied genes: x2 value for all studied loci was 0,008 – 1,96. Analysis of milk producing ability data in groups with different genotypes by locus of CSN3 gene showed that the highest indexes of milk yield were stated for group of cows with genotype CSN3**aa. Animals with genotype CSN3**bb had the highest fat percent, animals with genotype CSN3**aa - the lowest. Analysis of milk yield indexes showed that animals with homozygous genotypes BLG**aa and BLG**bb showed lower average milk yield than animals with genotype BLG**ab on 130 and 570 kg, respectively

During the investigation of nuclear DNA of boas of Belarusian meaty breed there was studied the polymorphism of EPOR, MUC4 and IGF-2 genes with the further determination of frequency of alleles and genotypes. Among boars tested for the polymorphism EPOR gene there was stated high percentage of heterozygous samples (EPOR**st): 43,3% for Belarusian meaty breed boars and 66,7% for Belarusian Kripnaya Belaya breed. In course of analysis of the genetic structure by MUC4 gene there was revealed the predominance of animals with the desirable d allele combination (MUC**cc): 60% for Belarusian Kripnaya Belaya breed and 82,2% for Belarusian meaty breed; by IGF-2 gene with homozygotic manifestation of recessive alleles: 46,4% and 63,4%, respectively. In the conditions of the Republic of Belarus there were determined the preferred boar genotypes with EPOR, MUC4 and ICF-2 genes and combinations which made it possible to increase the fattening and meaty qualities of posterity. The research results showed that in the selection breeding schemes it was necessary to consider not only maternal genotype, but also male genotypes giving preference to EPOR**st, MUC4**ss and ICF-2**qq genotypes

Analysis of influence of boar genotype by MUC4 gene on viability of progeny was realized in the conditions in the Republic of Belarus, as well as the evaluation of possibilities of association of polymorphic variants of gene with fattening and meaty qualities of obtained from the boars progeny were conducted. In course of studies there was analyzed the polymorphism of MUC4 gene at producer boars of studied breeds. There was revealed high occurring frequency of desirable allele MUC4**c and MUC4**cc genotype in all studied populations. Boars of Belarusian Meaty breed with genotypes MUC4**cc by MUC4 gene authentically (P less than 0,01) exceeded boars with genotype MUC4**cg according to piglet viability indexes at weaning period on 5,6%. For the further evaluation of the potential role of MUC4gene in marker selection there was realized determination of relations between genotypes of studied marker and other economic traits of swine (fattening and meaty traits of boar progeny). There was stated the authentic increasing of fattening and meaty traits of stores obtained from boars with homozygous genotype MUC4**cc in comparison with progeny fathers of which in their genotype had mutant allel MUC4**g. For the forecasting and modeling of genotypes resistant to colibacillosis there was presented a scheme of selection boars and sows of different genotypes by MUC4 gene for the increasing of progeny viability. According to the scheme the preferred selection was MUC4**cc x MUC4**cc. This selection was recommended for the self-replacement and creation of nuclear stock

Determination of genetic structure of different population lines of Belarusian white-and-black breed in accordance with locus of kappa-casein gene (CSN3) was realized in the conditions of the Republic of Belarus. In course of study there were used DNA samples of Belarusian white-and-black breed cows (380 samples) and bioprobes of servicing bulls (83 samples). With the help of endonuclease Hindill there were revealed two alleles of kappa-casein (A and B) in DNA preparations. As a result of genetic typing of breeding animals by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) methods there were revealed three genotypes CSN3**AA, CSN3**AB, and CSN3**BB. The frequency of occurrence of desirable genotype CSN3**BB of Belarusian white-and-black breed of cows depending on breed and linear pertain varied from 2,2% up to 7,69%, for servicing bulls – from 0 up to 11,1% . The majority of homozygotic cows with undesirable cow genotype CSN3**AA belonged to the following lines: of Ruties Edward (2,31646 - 92,3%), Niko (86,0%), Vis Ajdal (933122 - 71,9%), Reflection Sovereign (198998 – 63,9%). The desirable CSN3**BB genotype in most of the cases was stated at Annas-Adema (30587) and Hiltes-Adema (37910) lines. Presence of heterozygote genotype predominated in Annas-Adema (46,1%) and Montvik Chiftein (36,3%) lines. Realized analysis of cow population lines of Danish and Holstein breeds showed that the average frequency of occurrence of CSN3**B allel was 17%, but lower concentration (15%) of CSN3**b allel was typical for the Danish breeds. Frequency of occurrence of CSN3**B allel in Holsten lines was 18%. In was revealed that in 86,6% of cases bulls were the genetic carriers of CSN3**A allel and only 11,4% of animals had the desirable allel CSN3**B in their genotype