Nutrition of Salmonoid Fishes

Abstract

The effect of different levels of dextrin, alpha-cellulose and fat was studied in the diets of Chinook salmon fingerlings. No appreciable differences in fish growth for diets containing zero to 48% of dextrin and no alpha-cellulose were observed and no deleterious effects of high carbohydrate levels upon fish growth or health were detected. When the alpha-cellulose level of the diet was varied inversely with dextrin concentration, however, fish growth was retarded at very high alpha-cellulose concentrations, presumably as the result of the increased dietary bulk. Small amounts of alpha-cellulose in the diet apparently increased the efficiency of protein utilization. Replacing dextrin isocalorically with corn oil inhibited fish growth and decreased protein synthesis. Since carcass fat content increased markedly, a considerable portion of the dietary fat was absorbed. In addition, the effect of different carbohydrate sources was examined. When glucose, maltose, dextrin and potato starch were compared, fish growth rate was observed to decrease with increasing carbohydrate molecular weight. Sucrose produced a growth comparable to that with glucose while with fructose fish growth rate decreased 20%. Galactose gave retarded growth but did not result in increased mortalities or demonstrable abnormal pathology. Glucosamine as a carbohydrate source yielded the lowest growth of any of the carbohydrates tested.