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The paper presents the study results of the various recipes of production trout mixed fodders produced by LLC "RybProm" on the condition of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) during its cultivation in cages in comparison with the feed produced by Coppens. The physiological condition of the studied fish was evaluated, haematological, biochemical studies and pathological and anatomical autopsy were carried out. It was shown that the feed coefficient in the control group was 1.2, and in the experimental feeds from 1.3 to 1.5. Of the three studied feeds, the feed "Recipe #3" is practically not inferior in feed coefficient and growth rate to the control group. The conducted researches at the cage trout farm showed that the feeds of domestic production correspond to imported analogues. All studied feed recipes are safe for the health of rainbow trout and are sufficiently balanced for its cultivation in cages.

The article discusses feed additives with probiotic activity, the composition and methods of their preparation, an assessment of the situation of the use of synbiotic additives in compound feeds. Generalised literature data on the use of synbiotics in animal husbandry and aquaculture are presented, their advantages and disadvantages are revealed. A review of studies on the use of feed with probiotic activity in the diet of animals, birds and fish proves the high effectiveness of their use: there is an increase in survival, a decrease in feed conversion, an improvement in the microbiota and the general condition of the animal. Based on the review, a new substrate for growing bacterial strains based on a grain heap of wheat in the early stages of ripeness is proposed.

Ensuring a well-organised and sustainable feed base is the main condition for the development of animal husbandry, increasing its productivity and product quality. To ensure active growth and high productivity, probiotic feed additives are added to the feed, which increase the immune response of the host organism to pathogenic microorganisms, increases the conversion of feed and live weight gain. One of the main processes of feed production is extrusion, which can be cold, warm and hot. The hot extrusion process takes place at a temperature above 130℃ and cannot be used in the production of compound feeds with probiotics that withstand temperatures up to 85℃. During cold extrusion, the temperature reaches no higher than 70℃, which allows the extrusion of mixed feed mass, which contains probiotic feed additives.

The use of insects as raw materials for the production of feed additives is becoming an increasingly relevant and promising area of research. Nevertheless, this area requires numerous studies, including theoretical ones. The article presents the results of research on mathematical modeling of the process of obtaining feed additives in the form of fat and protein from the larva of the Black soldier fly (Hermetia illucens) in a screw press. Mathematical models have been obtained that allow theoretically determining the productivity of a screw press and its energy intensity in the processing of insect biomass. The models are based on the Navier–Stokes equation and Darcy’s law and take into account the design and kinematic parameters of the screw press and the rheological properties of the biomass of the face and the resulting fat.

The shortage of fish meal and fish oil provokes the search for alternative sources of these feed components. Insects that are part of the diet of animals, birds and fish, rich in protein and fat, can serve as such an alternative. The article presents the results of testing of compound feed for fish containing the fat of the larvae of the black soldier fly (Hermetia illucens) and a feed additive with probiotic activity. The use of the fat of the larva of the black soldier fly (Hermetia illucens) and a probiotic feed additive allows increasing the survival rate of fish from 90 to 95%, increase the conversion of feed and the average daily increase. The calculation of the economic efficiency from the use of compound feed, which includes feed additives of animal origin and additives with probiotic activity, showed an increase in profit when replacing compound feed made according to a standard recipe with compound feed with new feed additives. The economic effect of using compound feed with new feed additives amounted to more than 650 thousand rubles per year on small and medium-sized trout farms up to 20 tons per year.

The production of quality and inexpensive feed based on agricultural raw materials is the main way to increase the profitability and competitiveness of livestock production, ensuring its import substitution and high quality. It is known that in the structure of the cost of livestock products, 50-70% of all costs are accounted for by feed. Three variants of a mixture of crushed wheat grain and biomass of the black soldier fly larvae (Hermetia illucens) were extruded with the content of the latter 10, 15, and 20% by weight at different temperatures. The content of amino acids in raw materials and finished extrudate was determined. It was found that the feed mixture of crushed grain and black soldier fly larvae can be successfully extruded at a temperature of 121-135 °C. With an increase in the extrusion temperature in the range of 115-140 °C, the amino acid content in the finished extrudate decreases. The change in the content of insect larvae in the feed mixture does not affect the nature of the dependence of the amino acid content in the extrudate on the extrusion temperature and the course of the process. It was found that the content of amino acids in the extruded feed decreases with increasing speed with increasing temperature, regardless of the content of insect biomass. The rational range of the extrusion temperature of the feed mixture from wheat grain and insect larvae was determined – 121-127 °C, which ensures a reduction in the content of essential amino acids in the extrudate by no more than 30%. The extruded feed, which includes 15% of the biomass of insect larvae, contains 9.6 ± 0.13% amino acids, including 4.38 ± 2.01% of essential amino acids. The extrusion of insect larvae in a mixture with seeds of grain crops is a promising direction for improving the production of feed for fish and farm animals.

The article presents the results of a study of the effect of feed samples micronization on proteinogenic amino acids, such as: arginine, lysine, tyrosine, phenylalanine, histidine, leucine-isoleucine, methionine, valine, proline, tyrosine, serine, alanine. The optimal parameters of the micronization process of compound feed have been substantiated in order to increase the digestibility of feed and disinfection.

One of the promising directions in the fight against the emergence and spread of farm animal microbiota resistance factors is the development and search for feed additives that can inhibit the SOSresponse. SOS-response is one of the main mechanisms of the occurrence of mutations in bacteria. Plants used in traditional medicine can be a promising source of safe substances that reduce the SOS-response of bacteria. A screening of plants potentially containing substances with antiSOS activity was performed. During the initial screening, the E. coli MG 1655 pRecA-lux biosensor strain with ciprofloxacin as RecA inducer was used. Seven plants were identified whose extracts reduced the expression of the RecA operon. In further experiments on bacteria exposed to antibiotics, we identified four plants whose exstracts significantly reduced the mutagenesis rate of clinical E. coli strains: Austrian broom (Cytisus austriacus), greater celandine (Chelidonium majus), walnut (Juglans regia) and smooth sumac (Rhus glabra).

Probiotics are becoming more and more common means of combating intestinal diseases of various origins: infectious pathologies, chronic inflammation, autoimmune disorders. The complex action, coupled with low side effects, makes probiotics promising drugs, especially in veterinary medicine, with an increasing trend towards the inefficient use of antibiotics in the livestock industry. One of the main mechanisms of probiotics action - modulation of host immunity - is perhaps the most difficult and, at the same time, the most actively studied since it is crucial for therapy. Immunobiotics (probiotics that modulate the host's immune response) interact with various innate and adaptive immune cells, changing the expression of pro- and anti-inflammatory cytokines. This action is provided by both the cellular components of probiotic microorganisms and their metabolites and is primarily associated with the host's immunocompetent cells' pattern-recognition receptors, although other molecular mechanisms also exist. This review aims to briefly describe both the molecular mechanisms of immunomodulation by probiotics and the prospects for their use in veterinary medicine.

The article highlights the issues related to the study of physical and mechanical characteristics of bulk materials, namely internal friction coefficients in static and dynamic modes. An innovative device of the carousel type for determining the frictional characteristics of bulk materials is described, which allows to implement the tasks of practical determination of dynamic coefficients of internal friction. Presented the program, methodology and results of research on the practical study of the internal friction coefficient of typical bulk products of agricultural production in the range of linear velocities of displacement of layers from 0 to 2.79 m/s, the reliability of which is not lower than 0.878.