Total Replacement of Fishmeal by Soybean Meal with or Without Methionine Fortification in the Diets of Nile Tilapia, Oreochromis niloticus

Abstract

The high cost and competing demand for fish meal in fish diet has made the search for alternative ingredient very expedient. A 12 week feeding trial was conducted with Oreochromis niloticus to determine the effect of replacing fishmeal with soyabean meal and methionine on growth, nutrient utilization, haematology and plasma biochemistry. Four experimental diets (40% crude protein) were formulated, with Partial Soybean Meal (PSM) inclusion, No Soyabean Meal (NSM), Only Soybean Meal (OSM) and soybean meal and methionine. For 84 days, fish were fed at 3% body weight daily to triplicate groups of 15 fish (25.08 g0.04 g fishG 1 ) that were randomly allocated to twelve hapa suspended in 20 m 2 earthen pond. Results showed that Mean Weight Gain (MWG) and increase in length were significantly high (p<0.05) in PSM (22.77 g and 16.90 cm, respectively) and least in NSM (17.54 g and 14.63 cm, respectively). Specific Growth Rate (SGR) values were high in PSM (1.62) and OSM+M (1.55) and least in NSM (1.48). Fish fed OSM+M had the highest Parked Cell Volume (PCV, 20.66%), haemoglobin (Hb, 7.87 g dLG 1 ) and least White Blood Cells (WBC, 3.12x10 4 mmG 3 ), while NSM gave the least Hb (5.37 g dLG 1 ) and highest WBC (3.92x10 4 mmG 3 ). Serum enzymes AST (68.0 U LG 1 ) and ALT (46.66 U LG 1 ) were high in OSM+M and least in PSM (47.66 and 28.64 U LG 1 , respectively). The present study revealed that soybean meal can either be used to partially replace fishmeal or completely replace it with methionine supplementation, when growth, nutrient utilization and health status of O. niloticus are considered.