Evaluating poultry by-product meal, tomato pomace, and azolla with or without Natuzyme supplementation as sustainable alternatives to fish meal for Nile tilapia (Oreochromis niloticus)

Several studies have predicted that developing countries will be unable to afford fish meal as a primary aquafeed protein source in the future. This experiment evaluated the effect of replacing fish meal (FM) with poultry by-product meal (PBM), tomato pomace, and azolla growth, physiological, and histological parameters, besides their economic impact on Nile Tilapia (Oreochromis niloticus). A total of 270 fish were randomly allocated to 6 groups (initial weight average was 12.08 g). The groups are as follows: a fish meal-based diet (Tc), a poultry by-products meal-based diet (Tp), a T. pomace-based diet (Tt), Tt supplemented with Natuzyme (Tte), an azolla-based diet (Ta), and Ta supplemented with Natuzyme (Tae). Regarding the growth performance Tp, Ta, and Tae were secondary to Tc and followed by Tt and Tte. The hematological and biochemical indicators didn’t differ among groups. The Azolla-based groups had the lowest hepatosomatic index and the highest carcass fat and protein. Glutathione and interleukin-10 were higher in T.pomace and azolla enzyme-based diets. Malondialdehyde and tumor necrosis factor-alpha were lower in Tt, Tte and Tae. Standard histological findings were observed in the spleen, kidney, and liver among groups. Tp, Ta, and Tae significantly showed the highest absorption surface area (ASA) compared to Tt and Tte. The photomicrographs demonstrated negative expression of nuclear factor kappa B (NF-κB) in all treatments. Tp outperformed Tc 45% economically, and azolla matched PBM. It could be concluded that Azolla serves as a plant-based alternative. PBM represents a sustainable, cost-effective replacement for FM, reducing reliance on conventional marine-alternative proteins.