Effects of high-ash diets on growth, feed efficiency, and zinc status of juvenile Atlantic salmon ( Salmo salar)

Abstract

Juvenile Atlantic salmon (initial weight 3.9 g) were fed practical diets with similar levels of protein and energy,and graded levels of fish bone, for 98 days. The diets contained 10.5 to 17.5% ash and 100 ppm zinc after the addition of a commercial mineral supplement. When fish were fed a fixed ration, feed efficiency decreased (1.02 to 0.89) and their growth rate was reduced as the level of dietary ash was increased. When fed ad libitum, weight gains were similar in all groups. Protein digestibility was not affected by the level of dietary ash. Whole-body concentrations of iron and zinc declined markedly in all groups during the experiment. Even though clinical signs of zinc deficiency were not observed, small but statistically significant differences in whole-body zinc concentrations between treatments were detected. The results of this study suggest that dietary ash levels up to 17.5% are not detrimental to juvenile Atlantic salmon when the dietary zinc level is minimally 100 ppm.