Effects of Feeding Rates on Growth, Digestive Enzyme Activity, Serum Biochemical Parameters, and Body Composition of Juvenile, Genetically Improved, Farmed Nile Tilapia Reared in an In-Pond Raceway Recirculating Culture System

Abstract Fish culture using an in-pond raceway system (IPRS) is a new mode of freshwater aquaculture in China. This study was carried out to assess the effect of feeding rates on growth performance, serum parameters, digestive enzyme activity, and body composition of juvenile, genetically improved, farmed Nile Tilapia Oreochromis niloticus (GIFT) reared in an IPRS. Fish with an initial mean body weight of 6.25 g were fed twice daily at rates of 3, 4, or 5% body weight per day (BW/d) for 50 d. Results indicated that final fish body weight, weight gain, and specific growth rate of GIFT improved with increasing feeding rates from 3% to 5%. Growth of GIFT fed 5% BW/d was significantly higher than for those fed 3% BW/d; however, there was no significant difference from that of fish fed at 4% BW/d. Serum parameters and digestive enzyme activities were not affected by feeding rates. Lipid content in muscle and whole body increased with increasing feeding rates, and fish fed 5% BW/d had higher values compared with those fed 3% BW/d. Based on growth and physiological and biochemical variables, it could be concluded that a feeding level of 5% BW/d is suitable for juvenile GIFT fed twice daily reared in an IPRS.