The article shows the influence of physical (pH, temperature, aeration) and chemical (sugar content, sources of nitrogen and phosphorus nutrition) factors on the growth rate of strains of the genus Bacillus under conditions of solid-phase and submerged cultivation.
The optimal conditions have been determined: temperature of Bacillus subtilis growth 42 ºС, pH 6,7–7,3; Bacillus licheniformis – 37 ºС, pH 6,8–7,2; Bacillus megaterium 36–39 ºС, pH 6,4–6,9; with submerged cultivation - aeration with an intensity of 150 rpm; molasses concentration (for all studied strains of the genus Bacillus) 30 g/l; ammonium sulfate – 2,5 g/l; salts K2HPO4·3H2O+KH2PO4 – 30 g/l.
On the basis of the studies carried out, an optimized nutrient medium was created, the use of which makes it possible to increase the accumulation rate of bacilli up to 85,7 % in comparison with the initial medium.

In the article it was shown the spreading of Chlamydia infection in calves with clinical infection pathology in farms of Belarus Republic. It was revealed the importance of Chlamydia infection in the etiology structure of infection diseases and detected the most common Chlamydia species.

The epizootic situation of gastrointestinal diseases of calves caused by bacteria and viruses has been studied. The etiological structure of pathogens and the spread of bacterial and bacterial-viral associations in enteritis of calves in the studied farms has been established. Our research results prove that the leading place in the etiology of diseases of the gastrointestinal tract of newborn animals is occupied by associations of bacteria and viruses. 18 types of bacteria were isolated from calves with diarrhea syndrome and 4 types of viruses that caused the disease were identified. The largest share in the etiology of diseases of the gastrointestinal tract of young animals was occupied by the following bacteria as E. coli, salmonella, staphylococcus, streptococcus, yersinia, klibsiella, and proteas were identified much less frequently. The following types of viruses of the genera Rotavirus, Coronavirus, Enterovirus, Reovirus were also isolated. Isolation of associations of microorganisms in gastrointestinal diseases of calves with two pathogenic agents was 44,94 %; of three or more joints in 21,35 %; associations that included viral agents accounted for 33,71 % in various variations.

The article presents the results of studies of the immunogenic activity of vaccines produced by RUE «Institute of Experimental Veterinary Medicine named after S.N. Vyshelessky» in comparison with foreign analogues, as well as data on increasing the effectiveness of domestic vaccines.

The article presents data on a comparative assessment of the immunogenicity of «Pro-Vac Coryza-3» vaccines against avian hemophilia (South Korea) and «Volvak® AC Plus» (Germany) against infectious rhinitis in birds under production conditions. The results showed that these vaccines are harmless and reactogenic and is able to protect chickens from disease in the conditions of industrial production.

The article presents data on the selection of adjuvants and immunostimulants was carried out to increase the production of transovarian immunoglobulins, the optimal scheme of hyperimmunization of laying hens was worked out. It was found that the most optimal adjuvant for hyperimmunization of laying hens is Montanide IMS 1313 VG, the use of which leds to the development of specific antibodies in titer of 5,67 log₂. The use of Bacillus subtilis lipopolysaccharide as an immunostimulant leds to an increase in antiviral antibody titer at 0,17-0,83 log₂. The optimal scheme for hyperimmunization of laying hens is use of antigens in the form of monocomponents at a dose of 0,5 cm³ intramuscularly into the pectoral muscle region four times with an interval of 10-14 days, which increases the level of specific antibodies at 1,0-1,67 log₂.

Changes in spinal ganglia in canine intervertebral hernia have been studied. There is a reduction of capillaries, destruction of the endoplasmic reticulum, the Golgi apparatus, a decrease in AChE activity, and destruction of the nucleolus that can be observed. Three types of glial cells in the spinal ganglia were identified according to their structural characteristics.

In canine brain tumors pathological processes in nervous structures are accompanied by the destruction of dendrites and activation of pinocytosis process in neuroglial cells. The number of synaptic vesicles in axonal terminals in astrocytoma has been found to be reduced by 29,06 percent, in oligodendroglioma - by 28,13 compared with the physiological norm. On the basis of ultrastructural characteristics, two types of changes in the synaptic apparatus in cerebral cortex neurons have been identified.

The article provides data on the development of a method for obtaining transovarian immunoglobulins, one of the stages of which was to determine the optimal composition and ratio of antigens of viruses and bacteria for hyperimmunization of laying hens. As a result of the studies, it was found that in modern conditions of livestock farming with, the most common pathogens of infectious enteritis of calves are bovine viral diarrhea virus, bovine herpesvirus-1, rotavirus and coronavirus, as well as Escherichia coli bacteria, the production strains of which were used to immunize laying hens in the form of monocomponents. Hyperimmunization of poultry according to the developed scheme leds to the development of specific antibodies in titers – 5,0–8,0 log₂, which is 2,0–5,0 log₂ higher in comparison with the combined administration of antigens.

The complex preparation «Triclamizol» in a therapeutic dose and exceeding it by 3 and 5 times does not have a negative effect on the hematological and some biochemical (dynamics of total protein and albumins, the content of macro- and microelements in blood serum) indicators of the body of rabbits. The activity of аlanine aminotransferase, aspartate aminotransferase, amylase, and creatinine kinase in blood serum was within the physiological norm. The activity of gamma-glutamyltransferase increased depending on the dose of the drug by 76,63 % and 76,17 % (P<0,05) at doses of 300 mg/kg and 500 mg/kg of body weight on the 10th day after administration, respectively. On day 29, glutamyltransferase activity was at the level of control animals. In animals receiving the therapeutic dose, the body weight gain was 25,0 %, with a 3- and 5-fold increase in the dose of the drug by 19,56 % and 17,24 %, respectively, against 21,4 2 % in the control group.

The article presents data on pharmaco-toxicological characterization of a new veterinary preparation «Metrofarm».
The article describes the experience of determining acute toxicity of the drug, embryotoxic and teratogenic effects of the drug on laboratory animals.
The average lethal dose (LD₅₀) of the veterinary drug Metrafarm when administered orally for white mice was 62500 mg/kg of body weight. The drug belongs to low-hazard substances (class IV) with an LD₅₀ of more than 5000 mg/kg, according to GOST 12.1.007-76. The laboratory sample of the drug does not cause any deviations from the physiological norm in the clinical state in mice treated with the drug at doses of 1/10, 1/20 and 1/50 of the LD₅₀ dose.
It was found that the veterinary drug «Metrafarm» used in a toxic dose (30000,0 mg/kg body weight) to rats at various stages of pregnancy (periods of embryogenesis, organogenesis, fetal phylogeny and throughout the pregnancy period) does not cause pathological changes during pregnancy in rats, as well as deviations in the development of offspring, deformities, which indicates the absence of embryotoxic and teratogenic properties.

The article deals with the antimicrobial activity of the new disinfectant «Aldechas», created in the Republican unitary enterprise «Institute of experimental veterinary medicine» and the impact of its application on animal slaughter products.