Abstract:This experiment investigated the effects of dietary vitamin B6 content on growth performance, body composition, liver enzyme activities, and transaminase gene expression in juvenile rockfish (Sebastes schlegeli). Six experimental diets were formulated with different levels of vitamin B6: 2.08 (control group), 3.25, 4.16, 6.32, 10.17, 31.14 mg/kg. The juvenile rockfish average initial body weight was (36.35±0.06) g. After 9 weeks of treatment, the results showed that, with an increase in dietary vitamin B6 content, the weight gain rate and specific growth rate of the experimental fish initially increased and then decreased, with the largest changes seen in the 4.16 mg/kg group. The viscerosomatic index of the 4.16 mg/kg group was significantly higher than that of the control group (P<0.05). The hepatosomatic and intestine-somatic indexes of the 3.25 to 10.17 mg/kg groups were significantly higher than those in the control group (P<0.05). Muscle moisture content in the 3.25 to 31.14 mg/kg groups was significantly lower than in the control group (P<0.05). Crude protein and crude lipids of the whole fish and muscle showed increasing trends and then decreases. The activity of superoxide dismutase in livers increased at first and then decreased, with the 4.16 to 10.17 mg/kg groups showing significantly higher activity than the control group (P<0.05). Malondialdehyde content also decreased and then increased, with the 3.25 to 31.14 mg/kg group showing significantly lower content than the control group (P<0.05). Liver vitamin B6 content increased at first and then stabilized. The activities of glutamic oxalacetic transaminase and glutamic-pyruvic transaminase in the 3.25 to 31.14 mg/kg groups were significantly higher than in the control group (P<0.05). The relative expression level of GOT1 and GOT2 genes increased at first and then decreased, with the 3.25 to 31.14 mg/kg groups showing significantly lower expression levels than the control group (P<0.05). Relative expression level of GPT1 and GPT2 genes increased at first and then decreased, reaching a maximum in 6.32 mg/kg group. Relative expression of the tyrosine aminotransferase gene increased at first and then decreased, with the 4.16 to 10.17 mg/kg groups showing significantly higher expression levels than the other groups (P<0.05). Relative expression of the serine transaminase gene decreased, with expression levels in the 4.16 to 31.14 mg/kg groups significantly lower than in the control and the 3.25 mg/kg groups (P<0.05). A broken-line regression analysis of the WGR, liver vitamin B6 content, and GPT parameters showed that the dietary vitamin B6 requirement of juvenile rockfish with a body weight of 36 g was 3.52 to 6.32 mg/kg.
