Growth performance, body composition and metabolic response to feeding rates in juvenile Brazilian sardine Sardinella brasiliensis

A 6-week growth trial was conducted to evaluate the effects of feeding rate on growth performance, body composition, plasma metabolites and enzyme activities, and to determine the optimal feeding rate for juvenile Brazilian sardine. Fish were fed at six feeding rates, 2, 4, 6, 8, 10% BWday(-1) (body weight per day) and until satiation (10.3% BWday(-1)). The survival of fish fed at 2%-6%BWday(-1) was significantly higher (p<.05) than the survival of fish fed at the other feeding rates. The final body weight and specific growth rate significantly increased (p<.05) with increasing feeding rates while feed utilization decreased. Total proteins, cholesterol and triglycerides concentrations increased significantly with increasing feeding rates; however, there was no significant effect on glucose levels. Body protein and ash contents were not affected by the feeding rates. Whole-body lipid content increased significantly as the feeding rate increased, while moisture content had an opposite trend. Proteases and amylase activities significantly decreased with increasing feeding rates, while lipase activity was not influenced by the feeding rate. Our results suggest that low feeding rates stimulate mobilization of metabolites to supply energy for the maintenance of overall metabolism and digestive enzyme activities increase to enhance feed utilization. The optimum feeding rate of juvenile Brazilian sardine based on PRR as determined by the second-order polynomial regression was 5.45% BWday(-1).