CARBOHYDRATE UTILIZATION BY RAINBOW-TROUT IS AFFECTED BY FEEDING STRATEGY

A 16-wk experiment was conducted to compare the utilization of four ca rbohydrates by rainbow trout (Oncorhynchus mykiss) fed either continuo usly or four meals daily. The carbohydrates were glucose, maltose, dex trin and raw cornstarch, and were included at 32 g/100 g diet. Average initial body weight of the fish was 5.5 g, and fish were Fed at a res tricted rate of 2.0% body wt/d. Significant (P < 0.05) interactions be tween feeding strategy and carbohydrate were observed only for specifi c growth rate, final body weight, feed efficiency, and protein and ene rgy retained. These measurements as well as whole-body moisture and li pid concentrations were also significantly higher in the continuously fed trout than in the meal-fed trout. Liver weight:body weight ratio, liver glycogen concentration, and liver lipogenic enzyme activities ge nerally were higher in the continuously fed trout than in the meal-fed trout. Trout fed the glucose diet and those fed the maltose diet had higher specific growth rates, final body weights, feed efficiencies, e nergy retained, and whole-body and visceral moisture and lipid concent rations than those fed the starch diet. Trout continuously fed the glu cose and maltose diets also had higher glucose-6-phosphate dehydrogena se and 6-phosphogluconate dehydrogenase activities than those continuo usly fed the starch diet. The higher protein and energy retained and t he higher lipogenic enzyme activities in the continuously fed fish com pared with the meal-fed fish showed that in trout growing slowly due t o a restricted ration, continuous feeding improved the carbohydrate ut ilization and increased lipid storage by enhancing lipogenesis.