In the conditions of the Republic of Belarus there was realized a morphological study of bone marrow aspirates at different terms chicken of immunization against Gumboro disease which made it possible to analyze the state of immune system for the objective evaluation of immunological status. Research results showed that chicken immunization with a national liquid chick embryo viral vaccine produced on the basis of KMIehV-13 strain against Gumboro disease (infectious bursal disease) promoted the development of immunomorphological remodeling of bone marrow. Application of immunostimulants Alveozan and Nukleovit for poultry vaccination caused more expressed changes revealing in statistically reliable increasing of total number of myeloblastic cells in the majority of cases by means of increasing of immature cells, and then mature cells of granulocytic series, as well as quantity of lymphocytes and plasmacytes

Factors which increased milk productivity (age and continuance of service period) were studied in the conditions of an educational establishment of the Republic of Belarus by an example of cows of black-and-white breed. Dynamics of growth of milk productivity in course of 8 research years was presented. Analysis of interrelation between cow productivity and cow age was given. Mathematical calculation of relations between cow productivity indexes (milk yield, fat content, butter fat) and service period duration was given. Research results showed that increasing of an average term of economic use of cows and decreasing of duration of service period up to 90 days made it possible to increase dairy effiiemcy and herd reproduction, as well as obtain higher economic efficiency

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

An effort to demonstrate the mechanism of homeostatic alteration of high-producing cows at the period of increasing milking capacity and peculiar features of its changing in the conditions of introduction into cattle diets of carbohydrate containing and carbohydrate compensative additives was realized in the conditions of the Republic of Belarus. In course of the experiment there were used white-and-black breed cows of 3-4 lactations with body weight of 700 kg and milk yield over the last lactation of 7000-8000 kg of milk. Experimental cows in two weeks before the supposed calving were administrated with 50 ml of propylene glycol, 6 g of niacin and 50 ml of glycerin; and in course of 60 days after calving the administration of the additives was realized in doses of 125 ml; 6 g; 50 ml, respectively. Research results showed that application of mentioned above additives rendered the positive effect on cow liver that was proved by the improved hemic function of experimental cows: increasing of quantity of erythrocytes, hemoglobin, and hematocrit

Possibility of increasing of meat productivity of ducklings of Temp cross after application of duck parental forms of German selection was studied in the conditions of the Republic of Belarus. In course of study there was revealed the dynamics of changes of live weight and feed expenses for live weight gain of linear and hybrid ducklings; as well as their meat qualities were determined. In course of studied there were used linear and hybrid ducklings obtained after crossbreeding of parental forms of Belarusian and German crosses of Peking breeds. There were formed 8 groups of one-day old ducklings. In the father's line the first (control) group was presented by pure bred line T1 of Temp cross; in the second group – by hybrid NT1 x T1, obtained after the direct crossing of male ducks of NT1 with female ducks of T1 lines; in the third group – by hybrid T1 x NT1, obtained after the backcrossing of male ducks of T1 with female ducks of NT1 lines; in the fourth group the combination NT1 was obtained by NT1 x NT1. In fifth group the maternal line was presented by pure line of T2 Temp cross (control); the sixth group was presented by hybrid T2N x T2 obtained after direct crossing of male ducks of T2N line with maternal ducks of T2 line; in the eighth group the combination T2N was obtained by T2N x T2N. Research results showed that application of Germal ducks in schemes of crossbreeding rendered the positive influence on live weight increasing of ducklings of father's line. In the carcasses of hybrid ducklings of all studied crossbreeds there was stated the decreasing number of skin with adipose layer and increasing number muscles including the pectoralis

Determination of regular variations of macromorphological and topographical characteristics of thymus gland, spleen, thyroid gland, and atrabiliary capsules of swamp beavers (Myocastor coypus) at the postnatal ontogenesis was realized in the conditions of the Republic of Belarus. Taking into consideration active participation of immune and endocrine system organs in metabolic processes and vicarious and adaptive reactions there were revealed species and age-specific anatomical peculiar features of thymus gland, spleen, thyroid gland, and atrabiliary capsules of swamp beavers that made it possible to broader knowledge in the sphere of species, age-specific, breed and topographic anatomy

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

Analysis of the main indexes of embryo productivity of cow donors with a view to application of progestagenic intravaginal devices in technology of cattle embryo transplantation was realized in the conditions of the Republic of Belarus. Research results showed that application of progestogenic implants independently of the day luteal phase of sexual cycle in schemes of animal treatment made it possible to regulate the folliculogenesis of cows by mean of formation of new wave of follicles growth that could be used in increasing the efficiency of technology of transplantation of cattle embryos. Application of intravaginal devices in schemes of superovulation treatment of cows made it possible to obtain high-grade results of the main indexes of embryo production of donors in technology of cattle embryo transplantation. The technology of application of implant PRID in course of 7 and 9 days in the luteal phase of sexual cycle of donors proved to be the most optimal. It was determined that the indexes of quality composition of embryos, transplantability of fresh and frozen embryos obtained from cows induced by superovulation with application intravaginal devices corresponded to the control indexes. Application of progesterone extracting implants in the schemes of donor cows treatment schemes did not render influence on obtaining of viable animal yield after transplantation of biological material to recipients