Effects of the dietary protein to energy ratio on growth, feed utilization and body composition in Macrobrachium nipponense

Oriental river prawn (Macrobrachium nipponense) has been widely cultured in Asian countries. However, its nutritional studies are very limited. In the present 8-week study, we investigated the effects of dietary protein to energy ratio (P/E ratio) on the growth, feed utilization and body composition in juvenile M. nipponense (initial weight 0.302 ±0.03 g). Two-factor experiment was designed and nine semi-purified diets were formulated to contain three lipid levels (20, 80 and 140 g kg⁻¹) and three protein levels (330, 380 and 430 g kg⁻¹), producing P/E ratios from 16.5 to 23.4 mg KJ⁻¹ protein. The results indicated that the growth, survival rate and protein efficiency were dose dependently improved by the increased dietary lipid, but not dietary protein content. Increased dietary lipid content and/or protein content increased lipid accumulation in whole body, hepatopancreas and muscle, but did not change the feed intake and hepatopancreas weight. In conclusion, our present study indicated that M. nipponense is a species with relatively high-energy requirement. It could utilize dietary lipid content up to 140 g kg⁻¹, while the dietary protein with more than 330 g kg⁻¹ would not promote growth and protein efficiency. Taken together, 330 g kg⁻¹ dietary protein and 140 g kg⁻¹ dietary lipid level with P/E ratio 16.49 could be optimum for M. nipponense.