BREWING WASTE AS A FEED ADDITIVE FOR THE GROWTH OF AFRICAN SHARPTOOTH CATFISH

УДК: 636.033:614.95:619 DOI: 10.31588/2413_4201_1883_1_265_86

Abstract

Spent malt grains and spent beer yeast are brewing waste widely used in livestock and poultry diets. They are a source of biologically active substances, vitamins, amino acids and macro- and microelements. In this study, to explore the potential of using spent malt grains as a feed supplement for the nutrition and growth of African clarilid catfish (Clarias gariepinus), we propose treating the grains with a starter culture of spent yeast during the fermentation process. The novelty of this technology lies in the possibility of re-cultivating spent yeast microorganisms and using them as an enzymatic agent for the hydrolysis of plant materials. Physicochemical methods (pH-metry, conductometry, potentiometry) were used to study the properties of an aqueous solution of malt grains during hydrolysis. Incubation in a spent yeast medium for 12 hours leads to a decrease in the pH of the aqueous solution from 6.8 to 4.5 and an oxidation-reduction potential from 110 to 60 mV. The specific electrical conductivity (χ) of the grain solution after 8-10 hours of incubation reaches more than 6500 μS/cm. The obtained results demonstrate the ability of spent yeast microorganisms to actively participate in the fermentation process of grains, ensure a stable low pH level of the medium, demonstrate the antioxidant properties of the raw material, and increase the content of organic acids, mineral salts, and microelements. Microbiological analysis of the resulting product revealed a large number of starter microflora and probiotic microorganisms, naturally occurring alongside yeast, in the sample. No pathogenic or toxigenic microorganisms were detected. Observations of fish behavior during feeding with a feed additive based on fermented malt grains revealed that the experimental group of catfish consumed it intensively, were active, and exhibited facial solids, indicating normal intestinal microbiome function. Over two months of feeding, the final weight of African shaprtooth catfish doubled, with an average daily weight gain of 2.2-2.5%. Feed consumption per kilogram of fish growth was 0.79-1.02 kg, comparable to the control (commercial fermented feed). The proposed method can be used to create low-cost functional feed additives from brewery waste, which is much needed by fish farms.