Abstract:An 8-week feeding experiment was conducted to study the effects of different feeding levels on growth performance, intestinal digestive enzyme activities and serum physiological and biochemical indices of Asian swamp eel (Monopterus albus) at two different sizes [mean initial body weight: big-size (68.85±0.44 g) and small-size (26.67±0.17 g)]. There were four big-size groups which had 4 feeding rates (2.8%, 3.6%, 4.4% and 3.6% body weight/day); And five small-size groups which had 5 feeding rates (3.0%, 4.0%, 5.0%, 6.0% and 7.0% body weight/day). The stocking densities were 50 fry/4500-litre tank of big-size groups and 100 fry/4500-litre tank of small-size groups. Each group had three biological repeats. The results showed that with the increase of feeding levels for the two sizes of swamp eel, the weight gain rate, feed coefficient, liver body rate, and content of fat in the whole fish were significantly higher (P<0.05), but the content of protein in the whole fish had a decreasing tendency. When the feeding level was 4.4% and 5.2% for big-size swamp eel, the weight gain rate reached a peak, and there were no significant differences between the two groups. The activities of intestinal lipase and trypsin were significantly increased (P<0.05) with the increase of feeding level; serum superoxide dismutase (SOD) activity and total cholesterol (TC) content showed a trend from rise to decline; serum triglycerides (TG) content was rising. When the feeding level was 4.4%, the activities of SOD and lysozyme (LZM) reached the highest level among all the groups of big-size swamp eel. In pace with the rising of feeding level for the small-size groups, intestinal trypsin activity was increased significantly (P<0.05); the content of serum TG and TC rose gradually; the SOD activity was decreased; the content of blood sugar had a fluctuated trend. Compared with other groups of small-size swamp eel, the activities of SOD and LZM had higher standards when the feeding level was 6%. In conclusion, when the feeding level were 4.4% for the big-size and 5%–6% for the small-size respectively, the growth performance of swamp eel reached a better status.
