The review of literature sources has been given in the paper on opportunities exploring of secondary collagen containing secondary meat industry resources usage for food purposes due to conversion of their protein components difficult to digest.

Significance of protein from poultry processing by-product raw material in broiler feeding has been considered in the article. The research has demonstrated that broiler raising results with feeding rations containing plant raw material only, are worse significantly than with rations containing animal proteins. Additional stage of fermentation this animal raw material increases the effectiveness as feed in comparison with one stage process. Determined that feed protein additive from by-product raw material introduction into broiler ration improve broiler meat quality.

364,000 tons feather-and-down byproducts have been received after poultry slaughtering for meat in Russia in 2023 year. These byproducts may be raw material for feeds production with high protein content. Protein plays one of the leading roles among all the diet components. Diet protein part may be supplied at the expense of the assortment expansion of unused poultry industry components. Feather-and-down processing products are one of the cheap protein sources in poultry diets.

The technology has been considered in the paper for rational disposal of animal by-products and plant ma- terial mixture that includes hydro thermic treatment and enzymatic hydrolysis. Protein from different raw material mixture no gives in practically to FAO/WHO reference protein and to fish flour in essential amino acids content.

The mechanical and rheological properties of biocomposites based on polyethylene (PE) and keratin obtained by high-temperature shear deformation using an extruder-dispersant and by mechanical mixing in a Brabender plastograph are investigated. It is established that the method of high-temperature shear deformations makes it possible to obtain stronger materials. The biodegradation process of PE–keratin mixtures with different contents and dispersions of the filler is studied. It is found that the most intensive biodegradation process occurs in compositions obtained using an extruder-dispersant.

The technology have been considered in the paper on poultry processing byproducts rational utilization in- cluding this raw material hydro-thermic treatment and enzymatic hydrolysis. Protein being received from mixture of differ- ent byproducts is not inferior FAO/WHO reference protein in essential amino acids content.

Keratin-containing biocomposites of different dispersity were obtained based on polyethylene and polylactide. The dependence of the properties of compositions on the nature of the polymer matrix and the content of keratin was found. The X-ray microtomography has shown that the exposure of composites in soil leads to an increase in the porosity of materials. The capacity of the obtained materials for biodegradation was determined.

Eggshell membrane enzimatic hydrolyzate has been received, and it’s amini acid and peptide composition has been studied.

In the poultry industry, animal flour is often used, which is prepared from a mixture consisting of the remains of bones, soft tissues and feathers. They are rarely processed separately, especially for feathers, which have a very low digestibility. The technology of short-term high-temperature hydrolysis of feathers in a thin layer leads to the destruction of the keratin structure and increases the availability of its amino acids. This processing method achieves 86–88% of protein digestibility. The efficiency of using this feather meal (PM) in feeding makes it possible to reduce the cost of rations and improve zootechnical indicators.

It has been shown that when a fermented protein feed additive is added to the diet of broiler chickens, the presence of additional protein fragments was noted in the proteomes of the breast ( pectoralis ) and leg ( femoralis ) muscles of poultry. These proteins (actin, troponin, myosin heavy and light chains) are biomarkers of tenderness and water-holding capacity of meat (type M creatine kinase). The presence of additional isoforms of various complexes of the electron transport chain (cytochrome bc1 complex, or complex III of the electron transport chain), characterizing the effectiveness of this diet, was also noted. In addition, the introduction of fermented protein feed additive into the diet of poultry leads to an increase in the antioxidant capacity of the tissues of the breast and leg muscles of broilers and a decrease in the fat content in the tissues of the leg muscles.

The productive performance and meat quality were studied in broiler chicks fed diets supplemented with easily digestible animal derived protein additives produced by short-term intense thermal treatment and enzymatic hydrolysis of keratin- and collagen-containing wastes of slaughter and processing of poultry. The trial was performed on 4 treatments of Ross-308 broilers (50 birds per treatment, from 1 to 38 days of age). Control treatment was fed diet with fishmeal as animal protein source; in treatments 2 and 3 the fishmeal was substituted by enzymatic hydrolysate of feathers (keratin-containing wastes) with and without probiotic preparation, respectively; in treatment 4 the fishmeal was substituted by a mixture of enzymatic hydrolysates of feathers and collagen-containing wastes with probiotic preparation. It was found that average live bodyweight at slaughter age was higher in all experimental treatments in compare to control. The best results were found in treatment 3: live bodyweight at 38 days of age was significantly higher by 8.6% (P<0.001) while feed conversion ratio was lower by 6.7% in compare to control; this treatment also featured the best yields of carcass parts and meat quality.

The distribution of molecular weights (MW) of the peptides and anti-oxidative capacity (as oxygen radical absorbing capacity, ORAC) were studied in new protein feed additives produced by the short-term thermal hydrolysis and subsequent fermentation by proteolytic enzymes of the wastes and by-products of slaughter and processing of poultry. The properties of the new additives were compared with traditional protein additives, powdered milk (PM) and fishmeal (FM). It was found that the main peptide fraction in the additives is lightweight peptides with MW below 3 KDa. The highest amounts of this fraction was found in FM (83.58%) and in new "Fermented Additive" (FA, ca. 80%); PM and new "Hydrolyzed Additive" (HA) contained 65.16 and 53.58% of this fraction, respectively. The percentage of heavyweight peptides (> 10 KDa) in FM and FA was ca. 8% and 5%, respectively, while in PM and HA 17.55 and 32.77%. ORAC of hydrophilic fraction of all additives (to peroxide radical) was within the range of 152- 2000 µM of trolox equivalents (TE) per 1 g. The highest ORAC was found in FA (ca. 1980 µM TE/g), the lowest in FM (ca. 153 µM TE/g); ORAC in PM and HA was similar and fell within the range 400-520 µM TE/g. The conclusion was made that new protein feed additives have certain unique properties including anti-radical and antioxidative activity. MW of the most peptides within FA is below 3 KDa. Introduction of these additives to diets for animals and poultry can improve the quality of the feeds; allow for the saving on the expensive fishmeal; solve the problem of the utilization of poultry slaughter wastes and improve the ecological condition of poultry processing enterprises.

The efficiency of new protein additives based on the wastes of poultry slaughter and processing was studied on four treatments of Smena-9 broilers (35 birds per treatment, 1–38 days of age) in conditions of the Center for Selection Genetics “Zagorskoye EPH” (Moscow Province). Control treatment 1 was fed diets with fishmeal as animal protein source; in diets for treatments 2 and 3 fishmeal was substituted by fermented and hydrolyzed protein additives, respectively; diets for treatment 4 did not include any animal derived additives. It was found that the highest live bodyweight at 38 days of age was in treatment 2, significantly higher in compare to treatment 4 by 9.46

The paper presents experimental data on obtaining biogenic calcium from eggshells with maximum separation of the inner shell membrane and fine grinding of the shell. The results of studying the biological value of eggshell powder using laboratory animals are presented. The research results showed that during processing, the mass fraction of protein in the shell decreases almost 7 times - from 15.4% to 2.3%. Vortex mills are more suitable equipment for grinding. Eggshell is an effective source of calcium for the body, does not have acute and sub-acute toxicity. The availability of calcium from eggshell powder to the body is 2.6 times higher than that from a salt diet of inorganic calcium and is 81.7–87.9%. Enrichment of diets with eggshell powder has a beneficial effect on protein, lipid and mineral metabolism, as well as on the formation of the skeleton of growing organisms. The study of the biological value showed that the inclusion of eggshell powder in the diet in the amount of 1.5% (experimental group No. 2) and 3% (experimental group No. 3) did not lead to a decrease in traditional quality characteristics. As a result, an alternative to commercial proposals based on inorganic Ca salts for functional nutrition, cosmetics, biochemical and pharmaceutical production was found.

The effectiveness of protein additives based on the wastes of poultry slaughter in diets for broilers (cross Smena-9, 35 birds per treatment, 1-38 days of age) was studied as compared to the traditional diets with fishmeal as an animal protein source. Control treatment 1 was fed diets with fishmeal (FM); in diets for treatments 2 and 3 FM was substituted by fermented feed additive (FFA) and hydrolyzed feed additive (HFA), respectively, produced by the processing of slaughter wastes (feathers, intestines, and blood). The resulting levels of crude protein were similar in all treatments. It was found that the highest growth efficiency was in treatment 2: live bodyweight at 38 days of age was higher by 6.5% in compare to control (p<0.01), average daily weight gain higher by 3.6 g/bird/day; higher digestibility of protein from FFA resulted in feed conversion ratio lower by 1.9% in compare to control. Dressing percentage in this treatment was higher by 0.8% in compare to control, percentage of high-grade carcasses higher by 5.7%; as a result the European production efficiency index (377 points) was higher by 29 points in compare to control.