Growth promotion and dietary contribution assessment of three submerged macrophytes to Macrobrachium nipponense

The current study first investigated the effects of supplying three species of live submerged macrophytes on the growth and survival of the freshwater prawn Macrobrachium nipponese in tanks and compared the dietary contribution of the three species to M. nipponese using stable isotope analysis (SIA). Then, another 2-month feeding trial was conducted to evaluate the effects of supplementation of the three species of submerged macrophytes to a formulated diet on the growth, survival, immunity and intestinal structure of M. nipponese. The results showed that supplying Potamogeton crispus in tanks resulted in the highest final weight (FW) and weight gain (WG), followed by supplying Elodea nuttallii and Ceratophyllum demersum in the tanks. The diet feeding rate also had a significant main effect on FW and WG. The dietary contribution of the three submerged macrophytes to M. nipponense depended on the species of submerged macrophyte and diet feeding rate. When the diet provided was low (2% diet feeding rate), the dietary contribution of the three submerged macrophytes was not significantly different. When the diet feeding rate was 5%, among the three submerged macrophytes, P. crispus had the highest dietary contribution. Similar to the results obtained when live submerged macrophytes were supplied in tanks, M. nipponense fed formulated diets containing 15% P. crispus (P-15), 10% E. nuttallii (E-10) and 10% C. demersum (C-10) had a higher FW and WG than those of M. nipponense fed the control diet. The protease activities in the stomach and trypsase activities in the hepatopancreas were affected in M. nipponense fed formulated diets containing P. crispus and E. nuttallii compared with those of M. nipponense fed the control diet. Supplementing submerged macrophytes to a formulated diet did not significantly affect the MDA content, SOD and LSD activities in the hepatopancreas or intestinal fold height in M. nipponense. Based on these results, the three live submerged macrophytes supplied in tanks or supplemented in formulated diets improved the growth of M. nipponense. Among the three submerged macrophytes, P. crispus was the preferred macrophyte of M. nipponense.