Effects of lysine and tryptophan supplementations in plant protein-based diets on the performance of Nile tilapia (Oreochromis niloticus)

ABSTRACTIn this experiment, six soybean-based diets were formulated to be isonitrogenous and isoenergetic on a digestible basis. The treatments consisted of two levels of lysine (Lys) (0.25%, 0.5%) with three levels of tryptophan (Try) (0.05%, 0.1%, and 0.2%): D0.25°.05, D0.25°.1, D0.25°.2, D0.5°.05, D0.5°.1, and D0.5°.2 (Diets 1–6), where the subscripts and superscripts refer to the levels of Lys and Try, respectively. A total of 270 Nile tilapia (Oreochromis niloticus; initial body weight: 4.43g ± 0.01 g) were randomly assigned to 18 tanks with 15 fish per tank, three replicate tanks per treatment. After an 8-week growth period, the results showed that the interaction between dietary Lys and Try levels and the main effect of dietary Lys levels were not significant on the final body weight (FBW), while dietary Try levels significantly affected FBW (P < 0.05). Fish fed Try°.2 diets had significantly higher final body weight (FBW) compared with all the other dietary treatments, while fish fed Try°.05 had t...