Nutritional Performance of Extracted Soybean, Full-Fat Soya and Maize Gluten Meal Compared to a Fishmeal-Based Reference Diet for Juvenile Tilapia (Oreochromis Mossambicus)

Modern diets for aquaculture are highly complex and utilize a broad range of ingredients, including animal and plant byproducts. This study focused on the rationale of obtaining primary nutritional responses of tilapia evaluating two major ingredients, namely soybean meal and maize gluten meals by replacing fishmeal at set levels of incorporation. A two-onth investigation evaluated selected plant protein sources compared to fish meal protein in scientifically formulated diets for fingerling tilapia (Oreochromis mossambicus). Six nutritionally balanced diets: one reference (control) diet (fish-meal based diet), three selected plant proteins (solvent extracted soybean, full-fat soybean, and maize gluten) were substituted for the LT (Low Temperature dried) fish-meal-based control diet protein at 50% respectively, and the remaining diets were replaced with 75% inclusion of solvent extracted soybean and maize gluten meals. Results showed that solvent extracted soybean meal, 50 (SESB50), Full fat soybean, 50% (FFSB50) and Maize gluten, 50% (MG50) fed tilapia did not appreciably differ in their growth performance (percent weight gain of 279.36, 249.23, and 194.13% respectively) with a final mean weight of 14.95g being significantly superior (<0.05) for the fishmeal control (CO) group. Substitution of fish meal with solvent-extracted soybean and maize gluten at levels of 75% gave the poorest growth performance and Feed Efficiency (FE) (7.01g final weight, 51% FE). However, the MG50 diet also showed inferior feed utilisation performance. However, tilapia fed on a full-fat soybean diet (FFSB50) did not vary significantly from the control (CON) diet in terms of protein utilisation (ANPU) at 34.20% and 37.53% respectively. Whilst this preliminary study concluded that limitations on the use of the selected plant proteins in diets for tilapia are apparent, several approaches that could result in the future improvement of the nutritional value of soybean and maize gluten products for use in fish diets are also stated.