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.

The increase in demand for fish production drives the search for food strategies to maximize productivity. In this review, the nutritional implications of the use of exogenous proteases on fish growth were described. Exogenous proteases help in digestive processes, acting in the hydrolysis of macromolecules and in the release of smaller particles, such as amino acids and peptides. Dietary supplementation improves fish growth, mainly due to the availability and greater use of nutrients. The action of proteases is directly linked to better intake, feed efficiency and protein synthesis. On the other hand, enzyme activity depends on substrate and dietary composition as there are limitations on digestibility. Furthermore, in feed processing, thermal stability and the form of inclusion of the protease influence its efficiency. However, the increase in fish weight gain can offset the cost of including the enzyme in the diet. However, there are still gaps regarding the effects of protease in fish feeding, for example, enzyme: specific substrate and enzyme: digestive system ratio; and, stabilization technologies (mainly extruded diets), so further studies are needed.

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.