Nutritional limiting factors in duckweed and cassava leaf meal based diets for nile tilapia (Oreochromis niloticus)

Two feeding trials were conducted in recirculating water systems to determine the nutritional limiting factors in cassava leaf meal (CLM) and duckweed (DW) based diets for Nile tilapia. Fish (initial weight of 38.7+-0.17) were fed with eight isonitrogeneous diets (28 % crude protein) consisting of a control diet (100 % dietary protein from fish meal), one CLM based diet with 50 % dietary protein from CLM and 50 % from fish meal, four CLM based diets (100 % dietary protein from CLM) supplemented with different combinations of 0.1 % of crystalline amino acids (L-Met, L-Phe and L-Lys), and two CLM based diet with and without supplementation with 5 %of soybean oil for 42 days in the first feeding trial. Analysis of growth and food utilization parameters revealed that the main nutritional limiting factor in CLM based diets for Nile tilapia was low dry matter digestibility; the addition of Methionine (Met), Phenylalanine (Phe), Lysine (Lys), lipid energy did not improve the growth of Nile tilapia. Nutritional limiting factors of Duckweed based diet were evaluated in the second feeding trial. Fish (initial weight of 32.10+-0.13) were fed with eight isonitrogeneous diets (23 % crude protein) consisting of a control diet (50 % FM and 50 % soybean meal as protein source) and one DW based diet with 50 % dietary protein from DW and 50 % from fish meal, four DW based diets (100 % dietary protein from CLM) supplemented with different combinations of 0.1 % of crystalline amino acids (L-Met, L-Phe and L-Lys), and two DW based diet with and without supplemented with 8 % of soybean oil during the 40 day feeding trial. Analysis of growth and food utilization parameters revealed that the main limiting factors in duckweed based diets for Nile tilapia were low Met content and low TD s. The addition of Phenylalanine (Phe), Lysine (Lys) and lipid energy did not improve the growth of Nile tilapia.