MICROBIOMES OF HUMAN, LIVESTOCK ANIMAL GASTROINTESTINAL TRACTS AND OF FOOD PRODUCTS AND COMPOUND FEEDS: CONNECTIONS AND IMPACTS. PART 1

The physiological mechanisms of food digestion in humans and feed digestion in animals are determined by the structure of the gastrointestinal tract (GIT) and diet. Accordingly, humans are omnivores, while domestic animals are divided into ruminants, monogastric herbivores, and monogastric omnivores, and birds are divided into herbivores (geese, ducks) and omnivores (chickens, turkeys, etc.). The digestion and assimilation of food and feed depends not only on own mechanisms but also on the GIT microbiome. The location of the most important part of this microbiome and its composition depend on the species: in ruminants, it is the rumen microbiome, in horses – the cecum (it is a counterpart of the rumen), in humans and pigs – the intestine, in birds – the crop, gizzard and cecum. These microbiomes are in constant close connection with the host organism, and this connection is realized through numerous molecular mechanisms of interaction between bacterial cells and host cells and tissues. GIT microorganisms not only help to assimilate food (feed) by partially digesting it, but also secrete biologically active substances that have protective, stimulating and other beneficial effects for the host. In adult hosts, this GIT microbiota is well developed and stable, while in children and young animals it can be much more mobile and vulnerable. Food and feed contain many components that are a favorable medium for the development of microorganisms. Raw materials and components of animal origin are the most contaminated, while vegetable raw materials and components, as well as premixes, contain significantly fewer microorganisms. Among the microorganisms colonizing raw materials, food and feeds, coliforms, salmonellae and molds may be present. In young animals, the feed microbiota ingested into the GIT, even without taking into account obligate or opportunistic pathogens, can cause shifts or changes in the digestive microenvironment towards deterioration, which will have a corresponding impact on the efficiency of feed absorption and, through it, on the efficiency of feeding and animal productivity.