Influence of dietary vitamin C and bovine lactoferrin on blood chemistry and non-specific immune responses of Japanese eel, Anguilla japonica

A trial was conducted to determine the effect of ascorbyl-2-monophosphate Na/Ca (AMP-Na/Ca) and bovine lactoferrin (Lf) on blood chemistry and non-specific immune response of Japanese eel juveniles. Test diets with 32 or 762 mg AsA/kg diet, and with or without 500 mg Lf/kg diet were fed to juvenile Japanese eels (75.5 ± 4.4 g) once a day for 3 weeks. A diet without AMP-Na/Ca and Lf supplements was employed simultaneously as a negative control. Liver AsA content of fish fed diets containing 762 mg AsA/kg was significantly (P < 0.05) higher than fish fed diets containing 32 mg AsA/kg regardless of Lf level. Fish fed diets containing 762 mg AsA/kg showed lower serum glutamic oxaloacetic transaminase (GOT), lactate dehydrogenase (LDH), and serum total bilirubin (T-Bil) than fish fed diets containing 32 mg AsA/kg and the negative control group (P < 0.05), respectively. Lf was not a significant factor on those parameters. Fish fed diets containing 762 mg AsA/kg showed significantly higher lysozyme activity (LA) of mucus and serum, and bactericidal activity of mucus than the fish fed the diet containing 32 mg AsA/kg. Lf was a significant factor on serum LA, and there was an interaction between AsA and Lf on serum bactericidal activity. These results demonstrated that AMP-Na/Ca is an effective AsA source and higher level in the diet improved blood chemistry and non-specific immune function of Japanese eel. Moreover, the highest serum LA and mucus bactericidal activity were found in eel fed the diet containing the highest AsA content with supplemental Lf.