Influence of temperature and dietary-protein supplementation eitherwith free or coated lysine on the fractional protein-turnover rates in thewhite muscle of carp

The effect of protein quality and of supplementation of corn-glutenprotein with lysine on the growth, feed conversion and protein turnoverrates in white muscle was investigated in carp (Cyprinus carpio) acclimatedto either 18 or 25 °C. Fish fed the lysine-deficient diet showed asignificantly lower food intake, weight gain and feed-conversion efficiencythan animals fed the lysine-sufficient diets, regardless of environmentaltemperature. Coated lysine, compared with free lysine, proved to be asignificantly better way of supplementing dietary protein, as shown byfeed-conversion indices at 18 and 25 °C. White-muscle protein, RNA andDNA contents were not altered by dietary treatment or water temperature.Supplementation with coated lysine, but not with free lysine, significantlyincreased the protein-synthesis rate (K_S) at 18 or 25 °Cin comparison to lysine deficiency, although not to control values. Theeffiiency of protein synthesis (K_RNA) and retention (PRE)obtained for fish fed the coated-lysine diet, at 18 °C, reached controlvalues. At 25 °C PRE and protein accumulation rate (K_G)showed the following significant differences: lysine-deficient diet D, K_RNA or protein-related growth, at bothtemperatures.