In this work, an electron microscopic study of the structural features of enterocytes of intestinal crypts of the small intestine of hybrids obtained by crossing a yak and a cow of a black-and-white Holstein breed in comparison with the original species was carried out. The study indicated the similarity of the structure in the hybrids of all studied variants of crosses and the original species of borderless and goblet enterocytes of intestinal crypts of the duodenum and jejunum. The infinite enterocytes of the intestinal crypts of the hybrids had a well-developed smooth and granular endoplasmic reticulum, as well as many free ribosomes. The Golgi complex of crypt enterocytes in its development varied greatly, mitochondria were small, most often round in shape. Secretory granules had different electron density, more often moderate, matrix - average electron density. The cells of the Brunner glands were conical in shape with rounded apical ends, a well-developed Golgi complex, a smooth and rough endoplasmic reticulum, which formed extensive dilated lumens containing fine-grained material. The mitochondria were found to be predominantly rounded. Secretory granules completely filled the apical end of the cell and had a low electron density.

The gut microbiota and its development for the health of pets are currently being actively developed. The composition of the gut microbiome is found in the reduction of food intake, the state of the immune system of animals, productivity and growth in livestock content. Also found in the colon are unusual pathogen phyla that can serve as markers of fecal contamination in the environment. We conducted a study of the intestinal microbiome of 12 animals divided into two groups - calves and adult cows. Bacteria of taxa of taxa Actinobacteriota, Bacteroidota, Campilobacterota, Chloroflexi, Cyanobacteria, Desulfobacterota, Fibrobacterota, Firmicutes, Fusobacterota, Halobacterota, Elusimicrobiota, Euryarchaeota, Proteobacteria, Patescibacteria, Spirochaetota, Thermoplasmatota, Verrucomicrobia and a large number of unclassified bacteria were identified.It has been shown that the intestinal microbiome of calves differs from that of adult cows, and diarrhea affects the composition of the intestines of young animals, reducing the biodiversity of the inhabitants. In calves, the Shannon index ranged from 3.18 to 4.3, in adult animals from 4.41 to 5.24. Comparison of the gut microbiomes of healthy calves and calves with diarrhea was carried out using the Hutcheson t-test, the difference was significant (P<<<0.0001). > The main phyla of calf intestinal bacteria are Bacteroidota and Firmicutes, moreover, the diversity and number of microbial lines of Bacteroidota increases with age. Firmicutes of the families Lactobacillae and Lactobacillales_fa, as well as the family Selenomonadaceae, are markers of the juvenile age of animals. Calf-specific Bacteroidota are representatives of Tannerellaceae and Marinifilaceae. The microbiome of adult animals at the phylum level is distinguished by the presence of bacteria Verrucomicrobiota, Desulfobacterota, archaea Methanobacteria and Methanomicrobia. At the level of families and genera, the formed microbiome of cows has unique representatives of Bacteroidota and Firmicutes.Thus, we have presented data on the main representatives of healthy intestinal bacteria of cows and calves, which can later be used to diagnose the physiological state of animals, as well as in environmental studies to detect fecal environmental pollution.

The analysis of the incidence of livestock (cattle and pigs) of salmonellosis in the territory of the Irkutsk region during 2004-2016 was carried out. It was found that the incidence rate of cattle was 5.4±0.62 per 100 thousands livestock, pigs -4.0±0.04 0 /0000. The dynamics of reducing of the incidence of pigs was identified. Negative rates of increase in the incidence of animals were revealed. The epizootic index was 1.0. Salmonella of nine species (Salmonella dublin, S.enteritidis, S.choleraesuis, S.typhimurium, S.london, S.lindi, S.wernigerode and S.othmarschen) in cattle and five species (S.choleraesuis, S.enteritidis, S.typhimurium, S.rochdale and S.arizonae) in pigs were identified as the causative agent of the infection. S.dublin was dominated at the etiology of salmonellosis in cattle (75.1 %) (p≤0.05), S.choleraesuisin pigs (89.2±2.9 %) (p≤0.01). Salmonellosis in cattle was recorded in 11 districts of the Irkutsk region, in pigsin nine districts.

The article presents the results of microbiological studies of water from Lake Baikal in the spring period, and identifies a wide range of microorganisms that are tested for pathogenicity. It was established that many microorganisms of the enterobacteriaceae were pathogenic for laboratory animals. In 100 % of cases, pathogenic, sporogenous, anaerobic microorganisms were isolated - Cl. perfringens that multiply without access to oxygen, so, in the water mass.

The article presents the results of microbiological studies of the material taken from the seals’ corpses. The authors studied the taxonomic characteristics of microorganisms, their virulence and antibiotic resistance. It has been established that the following types of microorganisms are found in the seal: Citrobacter braakii, S. warneri, S. aureus, Escherichia coli serotypes O2, O18 and O39, Lactobacillus sakei, Aguamicrobium lusatiense. All pathogens isolated from the gastrointestinal tract were sensitive to 52.6% of antibiotics (ampicillin, cefuroxime, cefixime, gentamicin, amikacin, ciprofloxacin, ofloxacin, furadonin, Ceftriaxone) and resistant to 15.8% of antibiotics, two representatives of cephalosporins (cefaclor and ceftazidim) and ticarcillin. Conditionally pathogenic enterobacteria (Citrobacter braakii and Escherichia coli) isolated from muscles and liver were sensitive to all antibiotics.