Effects of dietary folic acid on growth, antioxidant capacity, non‐specific immune response and disease resistance of juvenile Chinese mitten crab Eriocheir sinensis (Milne‐Edwards, 1853)
2016
Wei, J.J. | Zhang, F. | Tian, W.J. | Kong, Y.Q. | Li, Q. | Yu, N. | Du, Z.Y. | Wu, Q.Q. | Qin, J.G. | Chen, L.Q.
An 8‐week study was conducted to determine folic acid requirement and its effect on antioxidant capacity and immunity in juvenile Chinese mitten crab Eriocheir sinensis (Milne‐Edwards, 1853), followed by a challenge assay with the pathogen Aeromonas hydrophila for 2 weeks. Folic acid was added to a basal diet at seven levels (0, 0.5, 1.0, 2.0, 4.0, 8.0, 16.0 mg folic acid kg⁻¹ diet), and a diet free of folic acid and vitamin B₁₂ was also included as a control. Crabs were fed twice daily in 32 tanks with 7.76–8.17 mg oxygen L⁻¹, 25.0–31.0 °C and 7.5–8.3 pH. Growth and feed efficiency were significantly greater in crabs fed ≥2.0 mg folic acid kg⁻¹, but not significantly different between crabs fed diets >2.0 mg folic acid. The superoxide dismutase activity and glutathione S‐transferase activity were highest in crabs fed ≥2.0 mg folic acid kg⁻¹, followed by those fed 0.5 and 1.0 mg folic acid kg⁻¹, and the control diet. The malondialdehyde content was highest in crabs fed the control diet, followed by those fed 0 mg folic acid kg⁻¹, and the lowest value occurred in those fed ≥0.5 mg folic acid kg⁻¹. Phenoloxidase activity and total haemocytes were significantly higher in crabs fed ≥2.0 mg folic acid kg⁻¹ than other diets. Crabs fed 2.0 mg folic acid kg⁻¹ had the highest lysozyme, acid phosphatase and alkaline phosphatase activities but the lowest cumulative mortality. The optimum dietary folic acid requirement by E. sinensis was estimated at 2.29–2.90 mg kg⁻¹ diet.
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