Partial replacement of fish meal with plant protein sources using organic acids to practical diets for juvenile yellowtail, Seriola quinqueradiata

An experiment was conducted to investigate the effects of phosphorus (P), citric acid (CA) and formic acid (FA) supplementation on growth and loading of nitrogen (N) and phosphorus (P) in juvenile yellowtail fed fish meal (FM) and alternate plant protein (APP) diets. Six diets designated as F49 (490 g kg-1 FM-based), F49 + P (490 g kg-1 FM with 5 g kg-1 inorganic P), F31 + CA (310 g kg-1 FM containing 200 g kg-1 APP with 5 g kg-1 CA), F31 + FA (310 g kg-1 FM having 200 g kg-1 APP with 4 g kg-1 FA), F23 + CA (230 g kg-1 FM containing 300 g kg-1 APP with 5 g kg-1 CA) and F23 + FA (230 g kg-1 FM having 300 g kg-1 APP with 4 g kg-1 FA) were formulated. Yellowtails were fed one of the diets for 12 weeks under on-site conditions at water temperature 22.027.0 degrees C. F49 + P gave the best growth, while F23 + CA the lowest. Specific growth rate and feed conversion ratio of F31 + CA were similar with control group. Addition of CA to APP diets significantly increased retention of P; hence, its excretion was lowered. The results of this study suggest that FM could be replaced up to 70% with the addition of 5 g kg-1 CA to a low P-containing plant protein sources diet without inorganic P supplementation in juvenile yellowtail diets, which in turn would enable a reduction in environmental pollution from aquafeeds.