Barley protein concentrate as a sustainable alternative to soybean meal in diets of hybrid African catfish (Clarias gariepinus × Heterobranchus longifilis)

This study aims to evaluate the potential of barley protein concentrate (BPC) as a substitution of soybean meal in the diet of African catfish hybrid ( Clarias gariepinus × Heterobranchus longifilis ) a hardy, fast-growing freshwater species. In line with this, two experiments were set up, firstly a digestibility trial to determine the apparent digestibility coefficients of the tested raw material in terms of crude protein, fiber and dry matter. Subsequently, a 10-week feeding experiment was performed with African catfish juveniles of 36.5 g initial weight in a closed recirculation system where increasing dietary levels of BPC (5, 10, 15, and 20%) were used to replace soy-based ingredients. In the in vivo digestibility trial, BPC exhibited appreciable apparent digestibility coefficients-84.5% for protein, 78.2% for fiber, and 78.1% for dry matter, supporting its potential as a viable dietary ingredient. Following the long feeding period diets with higher inclusion levels of BPC (BPC15 and BPC20) were found to negatively affect fish growth performance and protein utilization. The final body weight obtained was 193 and 147.4 g, respectively compared to control group (249.7 g). Similarly, a significant reduction ( P < 0.05) in protein production value was observed in those groups (37.4 and 23.5%) compared to the control (49.1%). Moreover, alterations in biochemical parameters (creatinine), digestive and metabolic enzyme activities (AST, amylase), and liver histology indicated signs of chronic stress in the BPC20 group. Overall, these findings suggest that moderate inclusion of BPC (up to 10%) can be beneficial, whereas higher levels of replacement may necessitate further nutritional balancing. • Barley protein concentrate (BPC) is a highly digestible, sustainable protein to replace soybean. • Moderate BPC inclusion (5–10%) enhances growth, protein efficiency, and metabolic performance. • High BPC levels (15–20%) compromise growth, protein retention, and trigger stress responses. • Dietary inclusion of BPC should not exceed 10%