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

ABSTRACT

In 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%): D_0.25°^.05, D_0.25°^.1, D_0.25°^.2, D_0.5°^.05, D_0.5°^.1, and D_0.5°^.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 the lowest FBW. Furthermore, no significant differences were observed among dietary treatments for proximate whole body composition. The results of this study indicate that Try can be supplemented at a level up to 0.2% in Nile tilapia diets containing high levels of soybean meal (44%) to maximize the growth of fingerlings.

KEYWORDS:

• Feed efficiency
• growth
• lysine
• Nile tilapia
• plant protein meal
• tryptophan

Acknowledgments

The authors thank two anonymous reviewers for their critical reviews, helpful suggestions, and comments. We also thank staff, researchers, and technicians for their assistance.