Influence of practical diet supplementation with free or coated lysine on the growth, plasma free amino acids and protein synthesis rates in the muscle of Ctenopharyngodon idellus

Four experiment diets were designed (purified diet , practical diet and practical diet with lysine uncoated or coated ) . Grass carp (mean weight of 7. 27 ±0. 5g) were fed separately in 12 fiberglass tanks (100cm ×50cm ×50cm) with 30 fish per tank. Every experiment diet was taken three repeats. The experiments lasted 9 weeks. Results indicated that grass carp fed with the purified diet showed a significantly higher growth ratio and protein synthesis rate ( Ks) than fish fed with the practical diet ( P < 0. 05) . Practical diet with coated lysineimproved the growth rate, feed conversion, balance of essential amino acid in plasma (BEAAp ) and protein synthesis rate ( Ks) in comparison with diet with lysine uncoated or deficiency. Coated lysine , but not free lysine , proved to be a significantly better way of dietary protein supplementation.