Effects of dietary folic acid on growth performance, body wall folate content, immune and antioxidant enzyme activity of juvenile sea cucumber, Apostichopus japonicus

Abstract

A 60-day feeding trial was conducted to investigate the effects of dietary folic acid on the growth performance, growth gene expression, body wall folate content, and digestive, immune and antioxidant enzyme activity of juvenile sea cucumber (initial body weight: 0.60 ± 0.01 g). Five diets were prepared and supplemented with 0 mg/kg (V0), 3 mg/kg (V1), 5 mg/kg (V2), 10 mg/kg (V3) and 15 mg/kg (V4) folic acid. The final body weight, weight gain rate and specific growth rate in the V1, V2 and V3 groups were significantly higher than in the V0 group (p < 0.05), while the feed conversion rate in these groups was significantly lower than in the V0 group (p < 0.05), and optimal dietary folic acid supplemented amount was estimated to be 7 mg/kg. The c-myc, MAPK-7 and FGFR-1 gene expression levels in the V1, V2 and V3 groups were significantly higher than in the V0 group (p < 0.05). In addition, the body wall folate content in the folic acid supplemented group was significantly higher than in the V0 group (p < 0.05). Moreover, the activities of lipase, pepsin and α-amylase in the V2 and/or V3 groups were significantly higher than in other groups (p < 0.05). The activities of alkaline phosphatase and lysozyme in the V2 group were significantly higher than in the V0 group (p < 0.05), and the activity of acid phosphatase in the folic acid supplemented group was significantly higher than the V0 group (p < 0.05). With dietary folic acid increasing, the total superoxide dismutase, catalase and total superoxide dismutase activities in V2 and/or V3 groups were significantly higher than in the V0 group (p < 0.05). In conclusion, the current results demonstrated the significant progress of dietary supplementation with folic acid on the growth and physiological response of juvenile sea cucumbers.