Bovine mastitis is a widespread infectious disease. In addition to the economic damages associated with reduced milk yield due to mastitis, the problem of food contamination by microorganism metabolites, in particular toxins, is also a concern. Horizontal transfer of microorganisms from animal populations to humans can also be complicated by antibiotic resistance. Therefore, bovine mastitis is relevant to the study of microbiology and veterinary medicine. In this study, we investigated the microbiome of milk samples from healthy cows and cows with different forms of mastitis from individual quarters of the udder of cows during first and second lactation. Total DNA was extracted from milk samples. The V3–V4 regions of the bacterial 16S rRNA genes from each sample were amplified to generate a library via high-throughput sequencing. We revealed significant dominance of several operational taxonomic units (OTUs) corresponding mostly to groups of Staphylococcus aureus, Aerococcus spp., and Streptococcus spp. In addition, we unexpectedly identified Streptococcus thermophilus in samples with high SCC quantities. We found some infectious agents that characterized summer mastitis. We demonstrated that in Central Russia, mastitis is associated with a wide variety of causal organisms. We observed some differences in the diversity of the two investigated farms. However, we did not find any significant difference among healthy, mastitis and subclinical samples according to their SCC status from either farms by principal component analysis. Linear discriminant analysis effect size (LEfSe) confirmed the presence of several indicator genera in farms from Moscow and the Tula Region. These results confirm the complex bacterial etiology of bovine mastitis.

Today, it is relevant to use feed additives of microbial origin based on the simplest fungi in the nutrition of farm animals and poultry. The exclusion of feed antibiotics has provoked interest in feed yeast and the study of the effect of yeast cultures on the gastrointestinal tract, microflora and rumen function. Kluyveromyces is a new non-traditional food and feed yeast that is isolated from various habitats, such as kefir grains, fermented dairy products, waste water from the sugar industry, and plants. A unique set of useful properties, namely rapid growth, thermotolerance and a wide range of substrates makes these yeasts especially attractive for use in various sectors of the food, pharmaceutical and biotechnology industries. Dairy yeasts are promising probiotic microorganisms that can break down lactose. In this regard, it is relevant to study the dairy yeast Kluyveromyces as a reliable source of yeast cells for the production of various enzymes, bioethanol, cellular proteins, probiotics, fructose and fructooligosaccharides, as well as vaccines with natural properties.

Relevance. Yeast and its derivatives have a comprehensive positive effect on poultry, but the effect of the carotene-synthesizing yeast Rhodotorula mucilaginosa on the microbiome and performance of broiler chickens has been poorly studied. The aim of this study was to investigate the effect of a microbial supplement based on the carotene-synthesizing yeast R. mucilaginosa before and after freezing on the microbiome and performance of broilers. Methods. The study was conducted on broiler chickens of the Smena 9 cross (n = 78). Three groups of 26 birds each were formed using the analog group principle. Battery cage technology was used for rearing. Birds in the control group received the basic diet; those in the first experimental group additionally received native yeast R. mucilaginosa (3 g/bird/day, assuming that the carotenoid content was 312 μg/g biomass); and those in the second experimental group received yeast after freezing and thawing at the same dose. Zootechnical parameters and the microbial composition of the rectum and cecum contents were studied using real-time PCR at 25 and 45 days. Results. The introduction of R. mucilaginosa , especially after freezing, increased live weight by 4.52%, average daily gain by 9.9%, leg weight by 11.91% (p ≤ 0.001), and breast weight by 2.72% (p ≤ 0.05). A significant increase in the number of Bacteroides spp. , Prevotella spp ., and Bifidobacterium spp. in the intestines was observed, as well as the complete elimination of E. coli from the cecum of the experimental groups. These data confirm the potential of using R. mucilaginosa in broiler feeding, but require further study.

Relevance. This article presents the results of a study ofthe effect offeeding different levels of concentrates on the rumen microbiota of sheep. Methods. The experiment was carried out on the basis of the physiological yard of the L.K. Ernst Federal Research Center for Animal Husbandry on Romanov sheep with chronic rumen fistulas according to Basov. The experiment was conducted using the method of groups of periods, the duration of each period is 30 days (n = 6). In the first period, the sheep received a hay-concentrate diet containing 20% concentrates, in the second — 30%, in the third — 40% of nutritional concentrates. At the end of each balance experiment, samples of ruminal contents were taken from all animals (n = 6) for a genetic study of the rumen microbiota. Results. Increasing concentrates to 40% resulted in a 6% and 7.5% reduction in total microbial mass compared with 20% and 30% concentrate diets, respectively. The amylolytic activity of the rumen after feeding gradually increased from 12.73 to 14.21 U/ml when the diet was changed to a more concentrated one. With an increase in the proportion of concentrates, the population of enterococci increases with a maximum at 30% of concentrates. The most intensive growth of the lactobacilli population is observed when feeding 30% concentrates (4.78∙10⁵ CFU/ml versus 3.18∙10⁵ CFU/ml at 40%). The ratio of QMAFAnM before and after feeding remained constant with a pronounced maximum at 30% concentrates. It was not possible to detect a consistent pattern in the change in the number of fungi in the rumen at different levels of concentrates in the diet. Metagenomic analysis showed an increase in the number of Lactobacillus spp., Bacteroides spp., Blautia spp., Streptococcus spp., Roseburia inulinivorans, Prevotella spp., with a decrease in the number of Bifidobacterium spp., Methanobrevibacter smithii, Methanosphaera stadmanae, Ruminococcus spp. in ruminal contents with an increase in concentrates by 20%, 30% and 40%. The highest contamination with microorganisms is observed when feeding animals 30% concentrates.

To date, the problem of mastitis in cattle remains relevant for both the industrial sector and scientific research. Despite numerous active investigations, the causes of this disease have not been fully established. It is postulated that several factors may be involved, such as bacterial pathogens, animal husbandry practices, and weather and climatic conditions. In this study, we selected cows from farms in Yakutia to investigate microbial isolates present in the milk of cows affected by mastitis and treated with antibiotics. Five identified Staphylococcus aureus isolates were investigated using whole-genome sequencing (Illumina sequencing and nanopore sequencing), followed by analysis of virulence factors in the genomes and cultural properties of the isolates. The profile of S. aureus virulence genes (exotoxins, cytotoxins, superantigen-like proteins, adhesins) was identified via WGS. Hemolysin gene (hla) was detected in all isolates. An investigation of the cultural properties of the isolates, specifically through hemolysis of rabbit erythrocytes and Western blot analysis of the culture liquid of S. aureus, revealed different expression levels of alpha-hemolysin among the strains. One isolate (17-21) exhibited the highest secretion level of about 320 ± 37 ng, both in the hemolysis test and immunoblotting assay. An investigation of the isolates’ antibiotic resistance showed that all isolates exhibited multidrug resistance, as confirmed by the presence of antibiotic resistance genes in these isolates. One isolate (7-7) exhibited the broadest range of phenotypic resistance and was resistant to all tested antibiotics (except clindamycin). Phylogenetic analysis suggested that the evolution of these isolates occurred independently in their respective ecological niches, although their transfer from cattle to humans, and vice versa, is possible. Isolates 7-7, 18-22, 33-40, and 35-42 are most typical to Yakutian cattle, while isolate 17-21 might have been introduced from a different region. To the best of our knowledge, this is the first in-depth study into a range of S. aureus isolates associated with mastitis infection in Yakutian cattle.