The effect of dietary lysine levels on growth and metabolism of rainbow trout (Salmo gairdneri).

Groups of rainbow trout (Salmo gairdneri; mean weight 5 g) were given diets containing 10, 12, 14, 17, 21, 24 and 26 g lysine/kg diet for 12 weeks. By analysis of the growth values the dietary requirement of lysine in this experiment was found to be 19 g/kg diet. A similar requirement value was obtained from a dose-response curve of expired 14CO2 (following an intraperitoneal injection of L-[U-14C]lysine) v. dietary lysine concentration. Liver concentrations of total lipid and carnitine and activities of lysine-alpha-ketoglutarate reductase (saccharopine dehydrogenase (NADP+, lysine-forming), EC 1.5.1.8) in the liver were not significantly different in fish from the different dietary treatments. Hepatosomatic index, however, was higher in those fish given low levels of dietary lysine.