The effects of dietary lipid and fibre levels on digestibility of diet and on the growth performance of sharpsnout seabream (Diplodus puntazzo)
In the present study, sharpsnout seabream (Diplodus puntazzo) were fed three experimental isonitrogenous diets composed of 45 g 100g-1 protein and varying lipid and fibre contents as follows: diet A: 45/10/1.5, B: 45/15/1.5 and C: 45/15/5. The effects of the diet composition were investigated by measuring digestibility, growth, carcass composition and haematological parameters. The apparent digestibility coefficients (ADCs) for proteins, fats and carbohydrates, measured at high (26˚C) and low (16˚C) water temperatures in laboratory conditions, were not affected by the diet or temperature treatments. Growth was evaluated in a seven-month trial using animals held in sea cages. The specific growth rate (SGR) showed no significant differences among the treatments while the feed conversion ratio (FCR) was significantly improved in the fish that were fed a low-fat diet. A significant increase in body fat was detected in the fish that were fed high-fat diets. The blood serum total lipid levels were elevated for the fish that were fed diet C. In conclusion, a diet containing a protein/fat/fibre ratio of 45/10/1.5 g 100g-1 can result in satisfactory growth and an improved FCR value when compared with diets with higher fat and/or fibre levels, demonstrating that the required fat level for sharpsnout seabream is lower than 15 g 100g-1.