Effect of dietary crude fat to NFE ratio on growth, feed efficiency and quality traits in juvenile shi drum (Umbrina cirrosa)

Shi drum (Umbrina cirrosa L.) is a suitable candidate for Mediterranean (marine) aquaculture because of its very fast growth in captivity. However, nutritional requirements of this Sciaenidae are not known. Thus, two complete extruded isoproteic diets with different crude fat to N-free extract ratio (CF/NFE: L=1.0 vs. H=1.5) were tested in juvenile shi drum to evaluate productive performances and quality traits of the final product. Experimental trial was conducted over summer 2001 using 4 groups of 200 fish (IBW = 8325 g) fed 2% BW. Growth parameters and feed efficiency were recorded and fish were submitted to morphometric, chemical and reological analysis. Considering a 4 months feeding period L-diet fed fish showed a significant greater weight gain than H-fed fish due to a higher specific growth rate (SGR) and a lower food conversion ratio (FCR). Chemical composition of whole body fish resulted in higher crude protein and lower lipids contents for animals of L-diet thesis. This suggests that the better rearing performances obtained with fish fed the low CF/NFE kind of diet are probably related to a more efficient utilization of dietary energy and/or crude protein. The main morphometric traits and textural properties of fish considered at the end of the study were not affected by dietary CF/NFE ratio.