One of the current challenges of global fish farming is developing plant‐based proteins as a feasible substitute for fishmeal in the formulation of aquafeeds. Substitution levels of fishmeal with hydrolyzed soybean meal (HSM) in diets for silver catfish (Rhamdia quelen) were evaluated for growth, protein metabolism and antioxidant activity. The experiment was carried out in a recirculation system of 20 tanks of 250 L. A total of 300 silver catfish juveniles were used to compose five treatments and four replicates per treatment. Levels of soybean hydrolysate (0%, 5%, 10%, 15% and 20%) were tested in diets (39% protein and 3,500 Kcal) for 60 days. Silver catfish growth was higher at all inclusion levels of HSM when compared to the control diet. No change was shown for body protein deposition. The production of nitrogenous compounds in the liver and muscle was also unaffected by any of the diets. The diet containing 20% HSM promoted an increase in the amounts of non‐protein thiols in the gills and brain. The HSM substitution levels of up to 20% of fishmeal in the diet increases growth and contributes to silver catfish antioxidant activity.

This study evaluated the substitution of fish meal with tilapia protein hydrolyzate (TPH) in diets for Silver catfish (Rhamdia quelen) by verifying the effects on growth, body composition, blood and biochemical parameters, and biomarkers of oxidative stress. Five isoproteic and isoenergetic diets (37% crude protein, 3,800 kcal/kg) were produced with different substitution levels of TPH (0%, 5%, 10%, 15% and 20%) for fishmeal. The hydrolyzate was obtained by enzymatic hydrolysis from carcasses of Nile tilapia (Oreochromis niloticus), which were exposed to swine pepsin enzyme at 36°C for four hours. The experimental design was completely randomised with five treatments and four replications. The inclusion of 20% TPH in diets for silver catfish increased the growth of Silver catfish juveniles. At levels above 5%, there was an increase in body protein deposition and the efficiency of oxidative metabolism.

Growth, biochemical and haematological parameters, and oxidative biomarkers were evaluated in juveniles of silver catfish (Rhamdia quelen). Fish were fed with tocopherol (0, 200, 300 and 400 mg kg⁻¹) during an experimental period of 60 days. Growth parameters of the silver catfish showed no changes with the addition of tocopherol in diets. Tocopherol favoured the deposition of polyunsaturated fatty acids in muscle tissue, changed the erythrocyte count and increased resistance of the erythrocytes. The inclusion of tocopherol at 300 mg kg⁻¹ in diets reduced oxidative stress in the brain, gills, liver and kidney. The addition of this compound improved the stability of biological membranes. The antioxidant protection exerted by tocopherol decreased ROS activity, and increased deposition of unsaturated fatty acids and oxidative stability, indicating favourable fish health. Silver catfish that ingested tocopherol in the diet obtained a higher body deposition of polyunsaturated fatty acids. Results of the present study recommend inclusion of tocopherol at 300 mg kg⁻¹ and higher in silver catfish diets.

Uma das demandas, na nutrição de peixes nativos, é a avaliação de fontes proteicas alternativas, que possam ser utilizadas em dietas. Este trabalho objetivou avaliar o crescimento e a composição corporal de juvenis de jundiá submetidos a dietas com diferentes níveis de farinha de minhoca. Um total de 300 exemplares, com massa inicial média de 15,6 ± 5,65 g, foram distribuídos em 15 tanques de polipropileno (250 L), durante 30 dias. O delineamento foi inteiramente casualizado, composto por cinco tratamentos (10%, 20%, 30% e 40% de inclusão de farinha de minhoca e uma dieta controle) e três repetições, com 20 peixes por unidade experimental. Os peixes foram alimentados duas vezes ao dia, recebendo 5% do seu peso vivo em ração dia-1. Ao final do período experimental, foram avaliados a massa final, comprimento total e padrão, taxa de crescimento específico, fator de condição e ganho em massa relativo. Também foi realizada análise de composição corporal, sendo determinadas a umidade, cinzas e gordura e proteína corporal, além da glicose sanguínea. Para a massa e comprimento total e padrão, não houve influência da adição de farinha de minhoca na dieta. Os níveis de inclusão de farinha de minhoca influenciaram a taxa de crescimento específico, ganho em massa relativo e o fator de condição dos peixes. A farinha de minhoca pode ser incluída em até 30%, na dieta de juvenis de jundiá, sem comprometer o crescimento dos peixes.