Introduction. Toxicity of new drugs should be evaluated in two species of laboratory animals, one of them being nonrodent species. In preclinical studies, dogs are used as second laboratory animal species. In toxicological research, analysis of organ weights is an important parameter to detect the target organs in test animals. Data on organ absolute and relative weights in animals aged 8–16 months are available in the existing scientific publications, however, none of these papers provide calculations relative to the weight of brain. The analysis of organ weights relative to the weight of brain is useful when changes in the normal dynamics of body weight are observed, since weight of a brain is more stable than weight of a body. Therefore, the objective of the present research is to determine absolute weights and reference intervals of mass coefficients of beagle dog organs relative to body and brain weights, and to compare the mass coefficients of dog organs, which have been calculated as a proportion of organ to body weight, to the data available in the literature.
Materials and Methods. The study was conducted at the “Home of Pharmacy” (Leningrad Region) in 2022. To calculate the reference intervals, the data on 25 males and 17 females aged 14–22 months that participated in control groups of various experiments were used. The electronic scales were used to record organ weights. The statistical outliers were not evaluated, since the number of animals was small. A nonparametric method was chosen for calculating intervals. To create the reference intervals, the absolute organ weights and coefficients calculated relative to body and brain weights were analysed. For further visual comparison of data retrieved by the authors to that available in the literature, the mean value and standard deviation were calculated in the Statistica 10 software.
Results. Absolute weights and reference intervals of mass coefficients of the heart, lungs with trachea, thymus, liver, spleen, kidneys, adrenal glands, brain, testes and ovaries were established relative to body and brain weights of beagle dogs aged 14 to 22 months. When compared to the data available in literature, discrepancies in liver weights of females were revealed, which may be caused by the different degree of organ exsanguination during necropsy. On the whole, the values obtained for the organs coincided with that in the publications, with the exception of thymus: since the dogs in the present research were older than animals described in the literature, the obtained discrepancy confirms the age-related involution of thymus.
Discussion and Conclusion. Availability of internal laboratory reference intervals enables correct interpretation of the obtained results of organ weight measurements, thus, prevents the false positive and false negative results. Further research in this area will reduce data scattering, which in turn will enhance the quality, reliability and reproducibility of scientific results. Moreover, in the future, this may result in reduction of the number of animals used in experiments.

Introduction. Today, the range of anthropogenic influences on the endothermic organism, including that caused by acoustic load, is growing so significantly that makes it necessary to search for the possible ways of preventing and correcting changes induced by noise exposure. Exposure of an organism to noise is attributed with neurohumoral mechanisms disbalance leading to catecholamine concentration increase in blood. This results in the microcirculation and tissue trophism disorder, cell membrane permeability increase, changes in structural and functional properties of integral and peripheral proteins, and lipid peroxidation intensity increase with the risk of hypoxia development. Therefore, the expedience of using succinic acid as an energy corrector should be justified experimentally. The present research aims at determining the stress- and adaptogenic properties of succinic acid in laboratory rats exposed to acoustic load.
Materials and Methods. The research was conducted in the period from 2022 to 2023 at the Central Research Laboratory of the Amur State Medical Academy (Blagoveshchensk). The objects of the research were 90 white outbred male rats, divided into three groups: 1st – intact group, the animals were kept in the standard vivarium conditions and were not exposed to any influence; 2nd – control group, the animals were exposed to acoustic load daily for 60 minutes during 21 days preceded by daily intraperitoneal administration of isotonic sodium chloride solution at a dose of 1 ml/kg right before the start of acoustic loading; 3d – experimental group, prior to the acoustic loading start, the rats were daily intraperitoneally injected with succinic acid at a dose of 1 ml/kg during 21 days. The acoustic load was created by playing back through the speakers the recorded sound of a running motorcycle engine with the level of sound pressure of 95–105 dB. Stressprotective effect was determined by the weight of the adrenal glands, thymus gland, spleen and the number of gastric mucosa erosions. The adaptogenic effect of succinic acid was determined on the 7th, 14th and 21st days from the start of the experiment by the duration of rats’ swimming in the water.
Results. The data obtained during the experiment has confirmed the adaptogenic effect of succinic acid in conditions of exposure to noise — the swimming time of rats from the experimental group increased by 25% (on the 7th day), by 27% (on the 14th day), by 32% (on the 21st day) compared to the control group. The stress-protective effect of succinic acid under acoustic load was manifested in prevention of thymus gland and spleen involution, on average, by 42% by the end of the experiment; and reduction by 2.5–3.5 times throughout the experiment of the number of gastric mucosa erosions in rats from the experimental group compared to the animals from the control group.
Discussion and Conclusions. The adaptogenic and stress-protective effect of succinic acid on the organism under acoustic load has been confirmed: administering the succinate to laboratory rats exposed to noise improves their physical endurance, increases the mass coefficients of the thymus gland and spleen in the experimental group against the background of statistically significant reduction of the number of gastric mucosa erosions. This is related to normalization of the energyyielding and constructive metabolism and oxygen homeostasis, when administering the succinic acid, which ensures improvement of the compensatory and adaptive reaction capacity as a feedback to stress.

Introduction. One of the diseases most frequently registered in companion animals is leptospirosis, a natural focal zoonotic infection caused by bacteria of the genus Leptospira, dangerous to humans. The main reservoirs hosts for spirochetes in wild fauna are rodents and insectivores, and in anthropurgic foci – domestic animals and cattle. Leptospirosis is widespread throughout the world, and despite the annual preventive measures, cases of disease in populations of susceptible animals continue to be detected and registered everywhere. To effectively combat the spread of infection, the comprehensive understanding of the etiological structure of leptospirosis is required. The aim of the present review is to summarise and analyse the data in native and foreign scientific papers on the causative agents of canine leptospirosis and the etiological structure of the disease.
Materials and Methods. The search for the papers was carried out in databases of electronic libraries and journals (NCBI, ResearchGate, Springer, etc.) using the keywords: leptospirosis, dog, microagglutination test, serogroup, serovar. Papers published during the last 10 years in Russian and English were studied. The results were presented in a PRISMA flow chart and a table.
Results. The conducted analysis of the prevalence of leptospirosis among dogs in different regions of the world indicates a generally adverse situation. The analysis of the etiological structure of the disease has revealed the presence of different serogroups and serovars depending on the geographical region, climate and vaccination history of animals.
Discussion and Conclusion. Understanding the real epizootic situation on canine leptospirosis is important not only for veterinary medicine, but for humanitarian medicine as well. Development and implementation of efficient preventive measures require constant disease monitoring and laboratory research, which includes, in addition to serological surveillance of leptospirosis, detection of the new leptospira isolates during disease outbreaks. This will reveal a complete picture of the infectious process and will enable modeling the new specific immune preparations for combating the disease.

Introduction. Brucellosis is a dangerous zoonotic disease indirectly and directly transmitted from animals to humans. Failure to comply with the veterinary requirements and rules in keeping animals and selling livestock products may result in a persistently adverse epizootic situation on brucellosis that can be prevented by timely vaccination. Vaccine efficacy may be affected by various factors, primarily by vaccine strain properties, which may change under adverse conditions (e.g. long-term storage). To mitigate the destructive effect of freezing, the bacterial cells are placed in various media, and therefore it is important to verify at morphological level the preservation of the structures of bacterial cells. However, no comprehensive morphological studies on the effect of various low-temperature storage conditions on the Brucella suis ultrastructure have been performed yet. The aim of the present research is to conduct a morphological analysis of bacteria Brucella suis (strain 22) to assess the features of the deep freezing effect on their ultrastructure in different conditions.
Materials and Methods. The study was conducted in 2024 at the Federal State Budgetary Scientific Institution “Federal Center for Toxicological, Radiation, and Biological Safety” (Kazan). The object of the study were suspensions of Brucella suis cells (strain 22) grown in different conditions. They were dehydrated and embedded in epoxy resins, then subjected to polymerization. The specimens for ultrastructural analysis were prepared according to the ultrathin section obtaining methodology, they were mounted using the lens-hoods, strained and viewed with a transmission electron microscope. Statistical processing of the research results was carried out in Statistica 6.0 and MS Excel programs using the Mann– Whitney test, with the initial significance level of α=0.05 and subsequent correction of significance level according to Bonferroni method (up to α=0.002).
Results. When assessing the effect of deep freezing on the ultrastructure of bacteria Brucella suis (strain 22) grown in skim milk and sucrose-gelatin media, no morphological differences from the native strain were found. Statistically significant differences from the native strain were revealed only in the group where freeze drying was used, but these differences were within the standard deviation.
Discussion and Conclusion. Based on the results of the morphological study on the effect of deep freezing on the ultrastructure of bacteria Brucella suis (strain 22), it can be concluded that skim milk and sucrose-gelatin are preferable media for low-temperature storage. In future, it is planned to study the features of the effect the other storage conditions have on the ultrastructure of genus Brucella bacteria to supplement the information in the strain data sheets. This work has an important practical value for creating the collections of microorganisms and developing diagnostic tools.

Introduction. The high prevalence of inflammatory processes in the organism of newly-calved cows, as well as the uncontrolled use of antibacterial preparations and growing number of drug-resistant pathogens, encourage researchers to continue search for the new methods and means of disease prevention and treatment. One of the important directions in this field is studying the competitive interactions within microbiota of animals. Analysis of different scientific sources allows us to conclude that, in the genital tract of cows, bacterial communities are formed under the influence of many factors, therefore our scientific interest is to study the vaginal microbiome of newly-calved cows in the climatic conditions of the Udmurt Republic, taking into account the seasonality and cow physiological state.
Materials and Methods. The study was conducted in 2023–2024 at the livestock farming enterprise of the Udmurt Republic. The objects of the study were 12 newly-calved Holsteinized black-and-white breed cows in different physiological state: healthy cows and animals diagnosed with metritis. The study was conducted using a number of methods: vaginal examination of cows, microbiological examination of vaginal flush samples using the conventional method.
Results. In clinically healthy newly-calved cows, the total number of microorganisms was within 87–94 CFU/ml, while in cows with metritis, this indicator varied within 90–443 CFU/ml. During the microbiological examination of the vaginal samples, the composition of collibacillus, staphylococcus, and bifidobacteria was found in microbiota of all experimental animals. In summer, a large number of E. coli were detected in sick animals, while in winter mainly bacteria of the genus Staphylococcus were found. As a result of competitive interactions between bifidobacteria and opportunistic microbiota in the vagina, in summer, the number of the Bifidobacteriaceae family representatives was insignificant (10¹) or completely absent.
Discussion and Conclusion. A correlation between the clinical status and seasonality of vaginal microbiota in newlycalved cows raised in the climatic conditions of Udmurtia was found. Further scientific research is needed to develop the efficient probiotic preparations preventing cervicitis and metritis in cows.

For successful development of veterinary dentistry in Russia, it is necessary to understand the background of the issue and the reasons of some acute problems faced by the modern public and private veterinary medical institutions in organisation of dental care for small domestic animals. The article aims to provide a brief overview of the history of veterinary dentistry in Russia and analyse the current state of the art in this sector. Among the main problems to be highlighted are the absence of the veterinary dentistry curricula in the sector-specific universities and the insufficiency of the normative documents regulating clinical activities.