Effects of feeding rates on growth, body composition and nutrient metabolism in striped bass ( Morone saxatilis) fingerlings

Abstract

A 12-week experiment was conducted to determine the effects of feeding rates on growth, morphology, body composition, and nutrient partitioning and metabolism in striped bass fingerlings with an average initial body weight of 38 g. The striped bass fingerlings were fed a commercial salmonid feed at different feeding rates from 0.5 to 4.0% (with 0.5% increments) of body weight per day (BW/day) at 19°C. The feed was dispensed continuously using automatic feeders and each feeding rate was administered in triplicate to groups of 15 striped bass fingerlings. Growth rate as measured by the percent body weight increase was significantly ( P<0.05) increased when the feeding rate was increased from 0.5 to 1.5% BW/day, and it reached a plateau with feeding rate of 1.5% BW/day. Feed efficiency did not show significant difference between fish fed 0.5 and 1.0% BW/day, but decreased steadily thereafter with feeding rate increased from 1.0 to 4.0% BW/day. Condition factor, hepatoand viscerosomatic indices, whole-body lipid content, and viscera protein, lipid and ash contents were significantly ( P<0.05) increased, whereas carcass to body weight ratio, and whole-body and visceral moisture contents were decreased when the feeding rate was increased from 0.5 to 1.0% BW/day. Liver soluble protein and glycogen concentrations, and glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, malic enzyme and isocitrate dehydrogenase activities were also significantly increased when feeding rate was increased from 0.5 to 1.0% BW/day. Mortality, carcass composition, whole body protein and ash contents, plasma glucose, protein, and triacylglycerol concentrations were not significantly different in striped bass fed at different feeding rates. Based on the growth and feed efficiency data, optimum feeding rate for striped bass fingerlings raised at 19°C was between 1.0 and 1.5% BW/day.