Abstract:An 80-day feeding trial was conducted to investigate the pantothenic acid dietary requirements of juvenile turbot. Six isoenergetic and isonitrogenous diets were formulated using fish meal and casein as a protein source. The basal diet was supplemented with calcium D-pantothenic acid at 6.24, 10.64, 15.02, 23.81, 41.40, or 76.57 mg/kg and fed to juveniles weighing (24.73±0.10) g. The results were as follows: 1) No significant differences in juvenile turbot survival rate (SR) were found between the dietary treatments (P>0.05) and the weight growth rate (WGR) and specific growth rate (SGR) increased as pantothenic acid levels increased from 10.64 to 76.57 mg/kg (P<0.05). For dietary pantothenic acid content greater than 23.81 mg/kg, the hepatosomatic index decreased significantly (P<0.05). 2) The crude protein and lipid levels of the whole body and crude protein levels of the muscle initially increased and then decreased with increasing dietary pantothenic acid levels, whereas the crude lipid content of the liver decreased (P<0.05). 3) The activities of the intestinal digestive enzymes Na+, K+-ATPase and hepatic cholinesterase (ChE) initially increased and then decreased with increasing dietary pantothenic acid levels, whereas intestinal creatine kinase (CK) activity increased significantly from 10.64 to 76.57 mg/kg (P<0.05). 4) Hepatic and serum catalase (CAT) and superoxide dismutase (SOD) activities were significantly lower in the control group than in the groups with calcium pantothenic acid-enriched diets (P<0.05). Turbot fed a 6.24 mg/kg pantothenic acid diet had a higher serum malondialdehyde content than those fed other diets (P<0.05). 5) Fatty acid synthetase (FAS) expression increased and then decreased with increasing levels of pantothenic acid. Lipoprotein lipase (LPL) expression was significantly up-regulated in the liver with increasing levels of pantothenic acid (P<0.05). In conclusion, appropriate levels of dietary pantothenic acid significantly improved intestinal digestion and absorption capacity, thus, improving nonspecific immunity and the expression of fat-related genes, and consequently, the growth and body composition of juvenile turbot. Based on broken-line regression analysis of WGR, the optimum dietary pantothenic acid requirement of juvenile turbot with a body weight of 24.73 g was 16.08 mg/kg.
