Evaluating the performance effects of unprocessed, citric-acid-treated, and fermented poultry by-products on Rainbow Trout

ABSTRACT Objective This study investigated the potential of unprocessed poultry by-products (UPB) and their bioprocessed forms as sustainable, cost-effective alternatives to fish meal in the diet of Rainbow Trout Oncorhynchus mykiss. Specifically, we evaluated the effects of UPB, fermented poultry by-products (FPB), and citric-acid-treated unprocessed poultry by-products (ACUPB) on growth performance, feed conversion ratio (FCR), gut beneficial bacteria, and health of juvenile Rainbow Trout. Methods Poultry by-products were collected and processed into three types: UPB, FPB, and ACUPB, which were used to replace fish meal in isonitrogenous diets at two substitution levels (50% and 70%). Seven experimental diets were formulated: control (0 UPB), UPB50, UPB70, ACUPB50, ACUPB70, FPB50, and FPB70. A total of 252 juvenile Rainbow Trout were divided and randomly placed into the treatment groups and fed these diets for 60 d. Growth, FCR, and survival rates were recorded. Blood samples were collected from the caudal vein for biochemical analysis, and tissue samples were analyzed for nutrient composition. Results Results show that both UPB and ACUPB improved the growth and FCR of Rainbow Trout relative to the control group (P < 0.05). The greatest growth rates were observed in fish that were fed ACUPB at a 50% substitution level (P < 0.05). Additionally, the ACUPB enhanced nutrient absorption and improved overall health markers (P < 0.05). However, diets with higher substitution levels (70%) showed a slight reduction in feed intake and growth efficiency (P < 0.05). Conclusions Poultry by-products, especially when bioprocessed or treated with citric acid, can partially replace fish meal in aquafeeds without compromising growth performance or health. The use of UPB and ACUPB offers a sustainable alternative for aquaculture, reducing reliance on marine resources while maintaining fish growth and nutrient uptake.