Dietary protein requirement of juvenile bluegill sunfish (Lepomis macrochirus)

Abstract

Five semi-purified diets were formulated with varying crude protein (CP) level (ranging from 20.77 to 45.69%) to assess the dietary protein requirement of juvenile bluegill sunfish (Lepomis macrochirus). Each diet was given to triplicate groups (20 fish per group, 1.20g per fish) for 10weeks. In this study, the weight gain (WG) values showed a general increasing trend with increasing dietary CP level up to 40.23%, and then no further improvement of growth was observed with further increase in dietary CP level. In addition, feed efficiency (FE) also improved with increase in dietary CP level; the maximum value was observed in fish fed diet with 40.23% CP. Besides, fish fed diets with 20.77 and 28.16% CP had significant higher daily feed intake (DFI) and lower energy retention (ER), lipid retention (LR) and nitrogen retention (NR) values than other treatments (P<0.05). Moreover, fish fed 20.77% CP diet with the highest starch content showed the highest hepatosomatic index (HSI) and relatively higher liver glycogen content than other groups. However, no significant difference in liver lipid content was observed among all dietary treatments. Fish fed diets with 20.77 and 28.16% CP had a relatively lower whole body protein and dorsal muscle protein content than other treatments. Based on broken-line regression analysis, the optimal dietary protein content for sunfish is about 41.51 to 42.37%. Statement of RelevanceThe main aim of this study is to quantify the optimum amount of dietary protein for juvenile bluegill sunfish (L. macrochirus).The research outcomes will develop formulated diets for L. macrochirus and will have good potential of being commercialized.