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 physiological experience spent on male pigs-manufacturers, we had been studied influence of various doses of selenium (10 mg, 20 and 30 mg) in structure premix on nutrients. It is established, that increase of level of selenium in mixed fodders for male pigs-manufacturers to 30 mg/kg especially promotes increase in degree of use in their organism of fat to 58,7%; (P less than 0,05), the digested nitrogen to 62,1%, calcium – to 78,3% and phosphorus – to 72,5%

Usage of boars of meat breeds Yorkshire, Duroc and Landrace of Canadian selection for crossing them with cross and pure breeds of sows promotes increase of fattening and meat-fat productivity of the obtained hybrids. The best parameters of feeding efficiency the hybrid young growth of combinations (BMхL)хL and (BMхL)хD at which the age of achievement of alive weight of 100 kg and a daily average gain has made 177,2 day (P less than 0,001) and 803 g (P less than 0,001), 179,5 day (P less than 0,001) and 801 g (P less than 0,001), differed at expenses of a forage of 3,38-3,40 fodder units accordingly

Research of the selection efficiency of boars of Belarusian meaty and Large White breeds for reproduction and productivity indices was realized in the selection and breeding centre Zadneprovski in the Republic of Belarus. The influence of 25-percentage level of boar selection for sperm production with the dominancy of relative average values of an initial population on statistically significant difference within the limits P less than 0,05-0,001 was proved. Application of an evaluation criterion of animal breeding abilities by the degree of frequency of departures from a population level with a value which reflects the intensity of selection in shares of an average quadratic deviation made it possible to raise the breeding value of boar of both genotypes in accordance with the productive qualities of descendants in comparison with average sizes of populations of two breeds on statistically authentic difference at P less than 0,05-0,001. Decreasing in the studied indicators of efficiency of offsprings concerning initial fatherly forms could be explained by a stronger influence of environment conditions rather than genetic predisposition of genotypes to the given traits

In course of a long-term selection breeding activities in the conditions of the Republic of Belarus on the basis of Belarusian Large White breed of swine there were created two high-productive lines - Delfina 37755 and Svitanka 3884. Individual selection of animals was realized in accordance with the main indexes of productive ability, development and conformation type. There were selected parent lines, there were used methods of intrastrain breeding and hybrid between lines, mild inbreeding on parental line. Bores and breeding sows were evaluated in accordance with their posterity productivity by means of a control feeding method. Productive indexes for Delfina 37755 line were 11,7 piglets, for Svitanka 3884 line – 11,9 piglets; age of live weight gain of 100 kg – 189 and 182 days, respectively; average daily weight gain – 735 gram and 749 gram; forage expenses – 3,5 and 3,51 fodder units; backfat thickness – 27,2 and 26,2 mm; ham weight – 10,9 and 11,2 k, 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

In the conditions of the swine breeding complex in the Republic of Belarus where had been applied the three-way crossing and self-replacement of swine herd there was studied the productivity of swine depending on duration of their embryonic development. There was developed new method of selection replacement gilts which made it possible to select a breeding swine flock with high adaptation abilities to the industrial housing conditions. Research results showed that the duration of pregnancy in the conditions of three-way rotational crossbreeding and self-replacement of swine herd was 114,5 +/- 0,03 days with variance between 103 and 121 days. In the majority of breeding sows (93%) the duration of pregnancy period was within the limits from 112 up to 117 days. Season of a year rendered influence on the duration of sow pregnancy: the longest one was in winter and spring, the shortest – in summer and autumn. With advancing age there was stated the increased duration of pregnancy period. Difference in duration for first-pregnant sows and sows with 8 farrows was 0,51 days. With increase of pregnancy duration there was noted the lowering of multiple fetation, but there was the increasing of live weight of piglets at birth, their growth energy and viability

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

The influence of polymorphism of gene IGF-2 on feeding and meat qualities of pigs of Belarusian Large White breed was studied. It is established, that frequency of presumptive preferable allele Q gene IGF-2 reaches 0,75-0,98% at boars of meat breeds and 0,34% - at Belarusian Large White breed. The young boars of breed with genotype QQ authentically surpass the analogues with a genotype qq on development, and feeding young pigs – on meat-feeding to qualities. Gene IGF-2 it is possible to consider as genetic marker of growth rate of pigs of the Belarusian Large White breed