Effects of dietary vitamin A on antioxidant responses of abalone Haliotis discus hannai Ino

A 240 d growth experiment was conducted in a re-circulated water system to investigate the effects of dietary vitamin A on growth and antioxidant responses of abalone Haliotis discus hannai Ino. Triplicate groups of juvenile abalone [initial mass was (0.96 ± 0.02) g, shell length was (17.70 ± 0.06) mm] were fed to satiation one of three semi-purified diets containing 0, 1×10~3, 1×10~6 IU vitamin A per kilogram diet, respectively. Results showed that the daily increment in shell length (DISL) of abalone in the treatment with 1×10~3 IU vitamin A per kilogram diet was significantly higher than that with 0 or 1×10~6 IU vitamin A per kilogram supplementation (P 0.05). Vitamin A deficiency (0 IU/kg) significantly elevated the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione reductase (GR) in the viscera of abalone (P 0.05). In muscle, the effects of vitamin A deficiency on SOD and GPX activities were the same as those in viscera, however, the activity of GR significantly decreased (P 0.05). Vitamin A deficiency significantly decreased the ratio of CAT to SOD (catalase/superoxide dismutase) in viscera (P 0.05). Nevertheless, it significantly decreased the ratio of GR to GPX in muscle (P 0.05). Compared with the supplement of 1×10~3 IU vitamin A per kilogram, excessive vitamin A (1×10~6 IU/kg) had no significant effects on the activities of CAT, SOD and glutathione-S-transferase (GST) (P 0.05), but significantly elevated GPX and GR activities in viscera (P 0.05). In muscle, the activities of CAT, SOD, GPX, GST and GR were significantly decreased by the excessive dietary vitamin A supplement (P 0.05). Compared with the supplement of 1×10~3 IU vitamin A per kilogram, vitamin A-excessive had no significant effect on the value of ratio of CAT to SOD either in viscera or in muscle (P0.05). The ratio of GR to GPX was significantly decreased in viscera, but significantly elevated in muscle in the vitamin A-excessive group (P 0.05). In conclusion, optimum supplement of vitamin A (1×10~3 IU/kg) was beneficial for abalone to maintain maximum growth and antioxidant system. Hypo- or hyper-vitaminosis A would decrease growth and the efficiency of scavenging reactive oxygen species (ROS) of abalone.