The article provides data on the biochemical properties of museum strains of Haemophilus parasuis The belonging of the strains of Haemophilus parasuis was confirmed in the polymerase chain reaction using the developed RUE «Institute of Experimental Veterinary Medicine named after S.N. Vyshelesskiy» test system for detecting the genome of Haemophilus parasuis.

Bovine viral diarrhea virus (BVDV) causes serious economic losses. BVDV has high genomic diversity: two viral diarrhea virus genotypes, with twenty-one subgenotypes for BVDV-1 and four subgenotypes for BVDV-2. Vaccines are important tools for reducing the economic losses caused by this virus. However, the strains of the vaccine match the antigenic profile of the viruses circulating in the area where the vaccine is. A phylogenetic study of 13 virus isolates circulating in the territory of the Republic of Belarus showed that the genetic profile of BVDV consisted in the overwhelming majority of subtypes BVDV-1f (76.9 %) and BVDV-1a (15.0 %), genotype 1, in one farm the subtype was found BVDV-2a genotype 2.

The article is devoted to the isolation of rotavirus from a sick calf and optimization of its cultivation parameters in the transplanted lines of homologous and heterologous cell cultures. Rotavirus isolate was isolated in MDBK cell culture, which was confirmed in polymerase chain reaction and neutralization reaction, from the faeces of a sick calf. A method of culturing the isolated isolate in homologous (MDBK) and heterologous (SPEV) cell culture has been worked out. The cultivation of rotavirus in an alkaline medium and its treatment with trypsin at a concentration of 20 mcg/ml and the introduction of trypsin into a supportive medium (15 mcg/ml) led to an increase in the titer of the virus to 8.0–8.25 lg TCD50/ml. It was found that the accumulation of isolated rotavirus in the rollers led to an increase in the yield of the virus and an increase in its titer to 8.5 lg TCD50/ml. The isolated rotavirus isolate has antigenic properties and leads to the formation of an immune response when administered intramuscularly to rabbits.

A culture of M. bovis was isolated from liver and spleen homogenate, from tissues and amniotic fluid of 8- and 6-month-old fetuses of cows with local tuberculous changes in the lymph nodes of the lungs. It serves as confirmation of the transplacental infection transmission. The transfer occurred due to filtering virus-like forms of tuberculosis mycobacteria, which were transformed into non-acid-fast, partially acid-fast and typical forms of tuberculosis mycobacteria in tissues, which can lead to the emergence of endogenous tuberculosis after birth or create an invisible reservoir of infection, because non-acid-fast forms of mycobacterium do not induce the development of hypersensitivity to tuberculin. In addition, the persistence of modified and typical mycobacteria in fetuses can lead to immunological tolerance to their antigens.

The results obtained confirm the correctness of the regulations on the isolated rearing of calves born in disadvantaged conditions, followed by fattening and delivery for slaughter.

This article presents the results of studies on the selection of adjuvants and the optimal scheme for hyperimmunization of Escherichia coli laying hens to obtain specific yolk immunoglobulins. It was found that to obtain specific yolk immunoglobulins, two immunizations of chickens with formalized Escherichia coli antigen (3x109 CFU/ml) with Montanide ISA 70 or Montanide ISA 206 adjuvant are sufficient. The use of Montanide ISA 70 in an adjuvant:antigen ratio of 70:30 by weight, respectively, and Montanide ISA 206 in an adjuvant:antigen ratio of 50:50 by weight, respectively, is equivalent.

The methods of obtaining of transovarial immunoglobulins for the development of veterinary biological preparation of a new generation are shown in the article. In the process of the research, the most effective method of isolating of transovarial immunoglobulins was determined - the method using organic solvents, and also the most optimal way to purify them by precipitation using PEG-6000, which allows to obtain the maximum result at relatively low cost. The results of the study of structural and functional features of the obtained yolk immunoglobulins of laying hens IgY in a comparative aspect are presented

DNA and antigens of mycobacteria tuberculosis (MBT) were detected in the cells of the tissues of a goat that fell with signs of lymphosarcoma (sharp hyperplasia of the lymph nodes and spleen, a positive AGID with an antigen or the diagnosis of leukemia - FLK - BLV- bovine leukemia virus). Latent tuberculosis infection was confirmed by the isolation of non-acid – fast MBT (cell wall-cell wall deficient – CWD) from decontaminated and filtered through a sterilizing filter of lymph node and spleen homogenates. In the populations of CWD MBT from lymphosarcomatous tissues a number of characteristic cell varieties were present which were previously found in isolates from the blood of a tuberculin-positive goat of the same herd, from the lymph node of a BLV-seropositive cow and directly from FLK-BLV.

In the isolates of lymphosarcomatous tissues along with MBT antigens, antigens that reacted with antibodies to BLV and had the same molecular weight as BLV antigens were found, which indicated the existence of a connection between virus-like forms of MBT and oncogenesis.

The influence of samples of 4 innovative materials developed at the Belarusian National Technical University on the basis of basalt fiber with additives of porcelain, oxides of copper, iron, and zirconium on the transplanted culture of cattle kidney cells was evaluated in this work. During the experiments, it was determined that the sample containing basalt, 4 % of porcelain and 4 % of FeO does not have a negative effect on the culture of MDBK cells. The material of this sample is promising for further use as a carrier for substrate-dependent cell cultures.

Sample materials showing a pronounced cytotoxic effect (basalt + 4 % porcelain + 4 % CuO, basalt + 4 % porcelain + 8 % CuO, basalt + 4 % ZrO2 + 4 % CuO) can be considered for the manufacture of bactericidal filters. This action is explained, obviously, by the manifested biocidal properties of copper, which is part of their composition.

The article presents data on the study of embryotoxic and teratogenic effects, irritating and allergizing properties, stability during storage of the new veterinary drug «Mastin», intended for the treatment of subclinical and clinical mastitis of cows.

It was established that the antimastitis drug «Mastin» does not have an embryotoxic and teratogenic effect, does not have irritating and allergizing properties. The veterinary drug «Mastin» is stable for 6 months under conditions of accelerated aging, which corresponds to a shelf life of 2 years from the date of manufacture, subject to storage conditions, and quality indicators meet the requirements of technical specifications.

The article presents studies to study effect of a new complex drug on immunobiochemical parameters of sheep. In our experiments on use of a new complex veterinary drug virococcid at a dose of 100 mg / kg of live weight, carried out on sheep spontaneously infested with parasitosis, significant positive changes in hematological parameters of blood and in systems of cellular and humoral immunity were revealed, which made it possible to normalize processes of hematopoiesis, which favorably affected clinical state of experimental animals, toxic effect on hepatocytes was not established.

The article presents data from scientific and industrial experience on the study of the therapeutic effectiveness of the complex drug «Activet MAXI» for arthritis in dogs. It was found that with its daily use at the rate of 1 tablet per 12.5 kg of body weight, the recovery of animals was observed mainly on the 25–30 day of treatment.

The article presents the results of research activities to establish the optimal rate of straw bedding in sections for dry animals, an economic assessment is given. For this purpose, the ethological reactions of animals, the comfort of keeping animals and thermometric indicators of the straw bedding were studied.

Experimental studies were carried out in the branch of the Agrofirm «Lebedevo» RUE «Minskenergo» Molodechno region. The objects of research were dry cows and heifers of the Holsteinized Belarusian Black-and-White breed, divided into four groups (1 control and 3 experimental), 30 heads each. The differences between the groups consisted in the amount of straw bedding applied. As a result of the research, it was found that for animals in sections 8×15 m, 4.5 kg/head is optimal, in sections with a division into a feeding zone (3×18 m) and rest (4.5×18 m) – at least 3.0 kg/head.