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 work carried out a morphometric study of the thymus of rabbits vaccinated with the associated vaccine against myxomatosis and viral hemorrhagic disease of rabbits (VHD) at a dose of 0.5 ml subcutaneously and treated with an insecticide preparation “Stronghold” (selamectin 6%) at a dose of 0.1 ml / kg at the withers … Chinchilla rabbits, live weight 2-2.5 kg, aged 6-8 months were used as experimental material. In total, 20 animals were examined. The thymus was examined by conventional histological methods. The nature of changes in the morphofunctional parameters of the thymus with the combined use of the investigated factors revealed a dependence on the time of application of the drug “Stronghold” in relation to the vaccine. Our studies on rabbit immunogenesis with simultaneous vaccination against myxomatosis and viral hemorrhagic disease of rabbits (VGBD) and treatment with the Stronghold insecticide with the active ingredient selamectin in the form of a 6% solution did not show significant morphofunctional changes in the thymus with increased stress load on a living organism.

The development of new technology methods for cryopreservation of animal cells has contributed to the introduction of stem cell banks for clinical use, including transplantation and regenerative veterinary medicine, and their further use to avoid problems of donors’ shortage. The research aims to determine the possibility of using the bone marrow of a domesticated yak as a source of stem cells after slaughter. Moreover, we should determine the suitability of post-mortem biological material for obtaining stem cells based on the index of proliferation and viability of cultured cells. Therefore, we used the following materials and methods: bone marrow, obtained from the femur of a domesticated yak in the post-slaughter period. Bone marrow samples were taken in compliance with the rules of asepsis in a sterile test tube. Thus, we added 0.25% trypsin solution to the biomass (the ratio of bone marrow to the solution is 10:1) and placed it in a refrigerator (t +40 °C) for 24 hours for enzymatic disaggregation. Furthermore, we carried out the culturing of the obtained cells in a CO2 incubator according to the standard method with passivation after the formation of a monolayer by 90%–100%. When culturing a suspension of cells obtained from post-slaughter bone marrow material, we noted the appearance of cell colonies six days after sowing. Periodic passivation of stem cells contributed to an increase in the biomass of actively proliferating cells. In addition, we found that stem cells isolated from post-slaughter bone marrow material of domesticated yak have significant proliferative potential, as evidenced by proliferation indices in the range from the first to the third passages and high cell viability. Thus, one can use the obtained post-mortem material in the form of the bone marrow of a domesticated yak as an additional source of stem cells. This post-mortem biological material is suitable for the isolation of stem cells 72 hours after the slaughter of an animal, which opens up the possibility of its transportation over long distances. The scientific novelty of the research is in the context of the international Convention on Biological Diversity, which means the variability of living organisms from all sources, including ecosystems and ecological complexes they are a part of. Within the strategy and action plan for the conservation of biodiversity of the Russian Federation, the ecosystem service of livestock production is significant for preserving the traditional way of life of the indigenous peoples of Siberia and the Russian Far East (it has regional and local significance). This global problem can be solved by (1) developing cell technologies for species not yet involved in it and (2) improving existing ones.