THE EFFECTS OF DIETARY FOLIC ACID AND VITAMIN B12 ON THE GROWTH PERFORMANCE, NON-SPECIFIC IMMUNITY AND THE DISEASE RESISTANCE OF JUVENILE CHINESE MITTEN CRAB ERIOCHEIR SINENSIS

In this study, we aimed to determine the combined effects of dietary folic acid and vitamin B12 on the growth, non-specific immunity, and the disease resistance of juvenile Chinese mitten crab Ericheir sinensis. The crabsinitial weight,(2.570.02) g were fed with 4 experimental diets containing 2 concentrations of folic acid(0 and 2.3 mg folic acid/kg diet) and vitamin B12 (0 and 0.2 mg vitamin B12/kg diet). Each diet group had 5 replicates and was fed for 8 weeks. This was followed by an Aeromonas hydrophila challenge for 2 weeks. E. sinensis fed with 2.3 mg folic acid/kg and 0.2 mg vitamin B12/kg showed significantly higher weight gain, specific growth rate, feed efficiency and survival rate than those fed without folic acid and vitamin B12 supplementation. The activity of phenoloxidase was the maximum in juveniles fed with 2.3 mg folic acid/kg and 0.2 mg vitamin B12/kg. Juveniles fed with both folic acid and vitamin B12 supplementation had the highest levels of total haemocyte count, lysozyme, and activities of acid phosphatase and alkaline phosphatase, followed by crabs fed with either folic acid or vitamin B12 only, and the group without folic acid or vitamin B12 supplementation was the lowest. Crabs fed with 2.3 mg folic acid/kg and 0.2 mg vitamin B12/kg exhibited the highest activity of superoxide dismutase but the lowest level of malondialdehyde and the cumulative mortality. These results indicated that folic acid and vitamin B12 had an interactive effect on the growth, non-specific immunity and the disease resistance of juvenile E. sinensis. The optimal concentrations of dietary folic acid and vitamin B12 should be 2.3 mg/kg diet and 0.2 mg/kg diet respectively.