The growth performance of southern catfish fed diets with raw, precooked cornstarch and glucose at two levels

The ability of juvenile carnivorous southern catfish (Silurus meridionalis Chen) to use different levels, kinds and physic state (glucose, raw cornstarch and precooked cornstarch) of dietary carbohydrate was evaluated in term of growth performance. All diets contained 100 g kg(-1) lipid and 16 kJ metabolizable energy. Three isonitrogeneus (400 g kg(-1)) diets were formulated to contain 150 g kg(-1) raw cornstarch, precooked cornstarch and glucose. Another three isonitrogeneus (300 g kg(-1)) diets were formulated to contain 300 g kg(-1) raw cornstarch, precooked cornstarch and glucose. A control diet was formulated with no carbohydrate containing 500 g kg(-1) protein. Each experimental diet was fed to four tanks of 10 fish (28.3 +/- 0.5 g) for 8 weeks at 27.5 degrees C. Specific growth rate (SGR) of 300 g kg(-1) glucose diet was significantly lower than those of other diets (P < 0.05). Feeding rates (FR) of 300 g kg(-1) glucose and control diets were significantly lower than those of the other diets (P < 0.05). Feed efficiency (FE) was significantly decreased with increased dietary carbohydrate level (P < 0.05). Feed efficiency of the 300 g kg(-1) glucose diet was significantly lower than those of the 300 g kg(-1) raw and precooked cornstarch diets (P < 0.05). The protein efficiency ratio (PER) was significantly increased with dietary carbohydrate level except that of the 300 g kg(-1) glucose diet, which was lowest among all diets (P < 0.05). The results suggested that both dietary starch and glucose were utilized for energy in southern catfish and had a protein-sparing effect. At 150 g kg(-1) inclusion level, the utilization of raw and precooked cornstarch and glucose did not vary significantly, but a higher dietary glucose level (300 g kg(-1)) had a markedly detrimental effect on growth in southern catfish.