Influence of dietary lipid on growth performance and body composition of the Gulf corvina, Cynoscion othonopterus

摘要

Based upon an iso-proteic dietary content of 40%, a 56-day experiment was conducted to evaluate the effects of incremental levels of dietary crude fat (2, 5, 8, 11, 14, 17, 20, 23 and 26%) on the performance of Cynoscion othonopterus juveniles, with an initial mean body weight of 32.86 +/- 0.48 g. Fish were reared in a clear-water, recirculating culture system, composed of 48 circular tanks of 250 L (0.4m(2) bottom area) filled with 200 L filtered seawater, at a density of 3 fish tank(-1) (15 fish m(-3)), assigning each treatment to five replicate tanks. Fish were fed approximately 3% of their wet body weight daily. Overfeeding was minimized while maintaining the feeding rate close to apparent satiation, dividing the daily ration into three equal portions. A clear dose-response effect of dietary crude fat was observed on growth of the Gulf corvina, C. othonopterus, with the best results corresponding to fish fed 11% crude fat, while growth performance was reduced as dietary crude fat departed from this level. These results were significant for specific growth rate and thermal growth coefficient data (P = 0.0283 and 0.0450, respectively), and although not statistically significant, the same pattern held true numerically for the majority of the other growth response variables and feed utilization indices measured. Quadratic broken line analysis of thermal growth coefficient data estimated a requirement for dietary crude fat of 11.4% for this species, with 95% confidence interval of 9.8 to 13.0%. Significantly increased lipid deposition, concomitant with reduced moisture content in muscle and whole body were observed in response to incremental levels of dietary crude fat. Intestine pancreatic lipase content tended to decrease with increasing dietary crude fat level, although this pattern was not statistically significant.