Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2423398 | Aquaculture | 2010 | 5 Pages |
The objectives of this study were to develop an amino acid test diet for Pacific threadfin (Polydactylus sexfilis) and estimate its lysine (Lys) requirement based on growth performance. A basal test diet was formulated using Pacific threadfin muscle and a mixture of precoated crystalline amino acids as the protein sources to achieve the same amino acid profile as in Pacific threadfin muscle with the exception of Lys. An 8-week growth trial was conducted with juvenile fish (initial body weight, 3.0 ± 0.1 g) fed eight isonitrogenous (35% crude protein) and isoenergetic (19.1 MJ/kg diet) semi-purified diets containing 1.26% to 2.91% Lys. The fish were cultured in an indoor flow-through system with 31‰ seawater at 25 °C. There were three replicate groups per dietary treatment. No mortalities occurred during the growth trial. Fish fed diets containing 2.23–2.43% Lys had higher specific growth rate, feed efficiency, protein efficiency ratio and protein retention than those fed diets containing less than 1.69% Lys. Excess dietary Lys also decreased growth of fish significantly. The basal diet (1.26% of Lys) resulted in higher liver but lower carcass to body weight ratio. Fish fed the diet containing 1.26% Lys showed significantly higher whole-body lipid and energy levels but lower moisture and protein levels than those fish fed the other diets. Broken-line analysis of the growth data indicated that the Lys requirement was 1.79% of diet (5.1% protein) under current culture conditions.