QUANTITATIVE DIETARY LYSINE REQUIREMENT OF ATLANTIC SALMON (SALMO-SALAR) FINGERLINGS

Triplicate groups of Atlantic salmon (Salmo salar) fingerlings, initial mean weight 4.7 +/- 0.2 g, were fed to satiation diets containing 1.24, 1.76, 1.90, 2.19, 2.45, 2.68, and 2.94% lysine and 24.1 MJ of gross energy per kilogram of diet (dry matter basis, DMB) for 70 d. The fish were reared in brackish water (10 ppt) at a temperature of 15 +/- 0.9-degrees-C on a 12-h photoperiod. The dietary requirement for lysine, estimated by broken-line regression of growth against dietary lysine level (DMB), was 1.99 +/- 0.11%, or 3.98% of the protein when protein was 50.0% of the diet. A dietary lysine requirement of 1.84 +/- 0.16% (DMB) was estimated from broken-line regression of expired (CO2)-C-14 (following an intraperitoneal injection Of L-[U - C-14]lysine) against dietary lysine concentration. Except for loss of appetite, resulting in low food intake and depressed growth, no nutritional deficiency signs were observed in fish fed a lysine-deficient diet for 140 d.