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

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