The optimal feeding regime for large yellow croaker Larimichthys crocea, with an emphasis on obviating raw fish diet in commercial farming

Abstract

Commercial farming of large yellow croaker Larimichthys crocea still relies on raw fish diet. The present study assessed the possibility to replace raw fish diet with a formulated diet containing 490 g/kg crude protein by optimizing feed and feeding management. In experiment I, fish weighing 10.8 g were fed with the formulated diet at either five frequencies (FF13, 1/3 meal/d; FF12, 1/2 meal/d; FF11, 1 meal/d; FF21, 2 meal/d; FF31, 3 meal/d) or at 1 meal/d but different times (FF11, at 6:00; FF11A, at 18:00), respectively. In experiment II, fish were fed at 2 meal/d with the formulated diet (FF21) or a quality raw fish diet (RF21). The final body weight (FBW), weight gain, feed intake and body lipid content, fish in/out ratio (FIFO) and waste outputs (nitrogen, phosphorus and carbon) were higher, whereas the nutrient and energy retention efficiencies (NRE, nitrogen; PRE, phosphorus; CRE, carbon; ERE, energy) were lower, in FF21 and FF31 than in FF13, FF12 and FF11. No significant differences were detected in FBW and weight gain either between FF21 and FF31 or between FF13, FF12 and FF11. The feed conversion ratio (FCR) and feed cost were higher in FF31 than in FF13, FF12 and FF11. The activities of superoxide dismutase (SOD) and catalase (CAT) in plasm, activities of glutathione peroxidase (GSH-PX) and CAT in liver, and malondialdehyde (MDA) content in plasm and liver were higher in FF31 than in FF11. No significant differences were detected in FBW, weight gain, NRE, PRE, CRE, ERE, body composition, feed cost, FIFO-, waste outputs, activities of antioxidant enzymes and MDA content in plasm and liver between FF11 and FF11A despite FF11A had higher feed intake and FCR compared with FF11. The FBW, weight gain, feed intake, FCR, body lipid content, feed cost, FIFO, waste outputs, activities of SOD and GSH-PX in liver, plasm CAT activity, and MDA content in plasm and liver were higher, whereas the survival, NRE, PRE and ERE were lower, in RF21 than in FF21. Our study indicates that 2 meal/d is the optimal feeding frequency for large yellow croaker, and completely replacing raw fish diet with the formulated diet in commercial farming benefits to increase fish survival and yield and to reduce feed cost, FIFO, waste outputs and body lipid deposition.