Abstract: This study aimed to examine the effect of dietary supplementation with low molecular weight chitosan (LMWC) on common carp growth and digestive enzyme activities. Basal diet group was used as control and LMWC groups at increasing gradient concentrations (0.25%, 0.50%, 0.75% and 1.0%) were established. Body weight gain, feed coefficient and the activities of amylase, lipase and trypsin in the hepatopancreas and gut were analyzed after feeding for 30, 45 d and 60 d. When compared with control group, body weight gain and the activities of amylase, lipase and trypsin showed a gradual upward trend, whereas an opposite trend was observed for feed coefficient with increasing dietary LMWC supplementation and feeding time. After 45 d and 60 d of feeding, a more striking increase in body weight gain and the activities of amylase, lipase and trypsin was found for 0.75% LMWC group compared with control group and 0.25%, 0.50% and 1.0% LMWC groups. For 1.0% LMWC group, the increasing trend of body weight gain and digestive enzyme activities gradually slowed down with increasing feeding time. Dietary LMWC supplementation in different proportions had different effects on digestive enzyme activities in common carps and the optimal dosage was 0.75%.

Key words: Cyprinus carpio, body weight gain, feed coefficient, amylase, lipase, trypsin, low molecular weight chitosan