REQUIREMENTS FOR LYSINE AND ARGININE BY RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

A series of experiments was conducted to determine lysine and arginine requirements of fingerling rainbow trout. Four groups of 30 trout each were assigned per diet and fed three times daily to satiation at 15-degrees-C. The diets contained varying levels of lysine and arginine. Weight gain of 13.7-g trout over a 6-week feeding period increased linearly with lysine level up to 1.4% of diet, but was not different at 1.4 and 1.6% lysine. Feed efficiency and nitrogen retention improved as the lysine level in the diet increased. Carcass protein content of trout fed diets containing sufficient lysine was higher than that of trout fed diets deficient in lysine. No significant differences in weight gain were shown between 11.6-g trout fed diets containing 0.47% arginine and either 1.5 or 3.0% lysine, indicating no apparent interactions between the dietary arginine and lysine levels. Weight gain of 12.4-g trout over a 6-week feeding period significantly (P < 0.05) increased with dietary arginine level up to 1.3%, but further increases in the arginine level did not have a significant effect. A similar trend was noted in feed efficiency, nitrogen retention and carcass protein content. Analysis of weight gain versus dietary lysine or arginine level indicated that the lysine and arginine requirements of young trout are 1.30 (3.71 ) and 1.41 (4.03)% of diet (protein), respectively.