Improvement of Nutritional Quality of Carbohydrate Ingredients by Extrusion Process in Diets of Red Sea Bream

Abstract

This study was conducted to examine whether the nutritional quality to red sea bream Pagrus major of carbohydrate ingredients in diets could be improved by extrusion processes. For this purpose juvenile red sea bream weighing 1.6 and 25g on average were fed diets with various gelatinized ratios (GR) which were adjusted by combining raw and gelatinized potato starch or rye at different levels (10, 25, and 35%) and proportions.
Fish which were fed diets containing extruded ingredients showed higher weight gain, feed efficiency, and protein efficiency ratio than those on diets containing raw ingredients. Irre-spective of the ingredient, the dietary performances were found to be proportional to the GR of the diet and reached a virtual plateau at around 50% GR. The daily feed consumption was inversely related to GR, probably due to the increase in digestible energy content of the diets. On the other hand, crude protein and lipid contents in the whole body and muscle were increased by elevation of GR.
Thus, availability of carbohydrate ingredients to red sea bream was found to be improved by the extrusion process and the GR of the diet should be at least 50% for optimal growth and feed efficiency of the fish.