Abstract
In order to investigate the responses of digestive enzymes to dietary changes, young carp were fed diets with different contents of protein and carbohydrate for 75 days. Fish meal was used as the protein source and potato starch as the carbohydrate source. Maltase, amylase and protease activities of intestine showed adaptation to the dietary change within a week, and these three enzymes showed generally higher activities in the groups given diets with 40-60% starch throughout the experimental period. Low growth rate was noticed only in the high starch diet group (90% starch) and a clear difference was not seen among the other three groups (20, 40 and 60% starch diets).
When four kinds of carbohydrate (maltose, sucrose, lactose and starch) were used as carbohydrate sources, maltase and amylase activities in intestine after 10 days feeding were high in carp fed the diets containing starch or lactose.
Intestinal protease activity of young carp clearly showed adaptation to the fish meal content in the diet when the starch content in the diet was kept constant. Growth rate increased in accordance with the increase of fish meal content in the diet.
