Bacterial contamination is an unavoidable finding of the semen collection process in boar and can lead in deleterious effects on semen quality and longevity if left uncontrolled. The purpose of this study is to identify the bacteria in extended boar semen and to select the effective antimicrobials to control of the contaminants. Of 116 extended boar semen samples submitted from eight AI centers in Korea, 39 (33.6%) samples were positive for bacterial contamination. Among 39 contaminated semen, most of them (84.6%) were contaminated with one or two bacterial species and there was no significant difference between two age groups (less-than or equal to 24 and greater than 24 month old). Stenotrophomonas maltophilia (n=18) was the most predominant bacterium followed by Elizabethkingia meningoseptica (n=12), phingomonas paucimobilis (n=12), Myroides spp. (n=5), Ochrobactrum anthropi (n=3), and so on. Enrofloxacin (72.9%), florfenicol (72.9%), bacitracin (49.2%) and tylosin (49.2%) showed higher sensitivity compared with penicillin (13.6%) or aminoglycosides (6.8%-18.6%). Brucella spp., Leptospira spp., Mycoplasma hyopneumoniae, Mycoplasma hyorhinis, Mycobacterium tuberculosis complex were not detected in semen by PCR.

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

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

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

Determination of the optimal doses of selenium inclusion into premix structure for breeding boars for the maintenance of their higher producing capacity was realized in the conditions of the Republic of Belarus. Selenium lack in boar rations caused the degenerative changes in seminal glands, low male germ cells concentration and lowering of spermatozoon motility, which subsequently decreased their producing efficiency. Research showed, that selenium inclusion in premix KS-1 structure in quantity of 30 mg per 1 kg in comparison with premix in 20 mg dose have improved the yielding productivity of mature boars: the average quantity of male germ cells per one ejaculate increased on 17,2%, the average quantity of born pigs from per one sow increased on 4,8%. The additional profit per one boar was on 6,06% higher than in control experiment

Development of a new method of boar evaluation taking into account their beef-making and fattening qualities as well as their posterity viability for the further selection of the best ones and for the culling and ranking of the worst ones was realized in the conditions of a large pig-breeding complex of the Republic of Belarus. Scientific and economic experiment was realized at the JSC Sozh, Gomel region (Belarus) at the pig-breeding complex with 108 thousand livestock heads of annual fattening. At a finishing stage of sow hybridization the combinations of Large White х Landrace and Large White х the Belarusian Meaty breeds were inseminates by boars of 990 synthetic lines (N11151 and N11146), the Belarusian Meaty breed (N3495), Landraces of the Polish (N40, N37, N78) and German selection (N11262, N11263, N11266), and also by a hybrid boar of 990 lines х Petren (N11145). Sow insemination was realized in three technological groups. Sows were selected taking into account their breed, age and last productive ability in order to avoid inbreeding. At the same time, each boar was checked up on the breeding stock for identical quality. The final estimation of boars was stated at the stage of achievement by their posterity of selling weight (before sending to a meat processing plant). The offered method made it possible to get an objective comparative estimation of breeding characteristics of tested boars in the conditions of a complex

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

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 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%