Dietary Vitamin B₁ And Vitamin B₆ Requirements Of Juvenile Rockfish （Sebastes Schlegeli）

Part1:This experiment investigated the effects of dietary vitamin B₁ content on growth performance,liver enzyme activities and serum biochemistry in juvenile rockfish（Sebastes schlegeli）.Seven experimental diets were formulated with different levels of vitamin B₁:0.87（control group）,1.83,2.85,4.72,8.81,16.37,30.64mg/kg mg/kg.The juvenile rockfish average initial body weight was（36.35±0.06）g.After 9weeks of treatment,the results showed that,with an increase in dietary vitamin B₁content,1)The weight gain rate and specific growth rate of experimental fish tended to increase,but there was no significant difference（P>0.05）.2)Liver transketolase activity first increased and then decreased,the 1.83-30.64 mg/kg group was significantly higher than the control group（P<0.05）,and had a maximum value at 8.81mg/kg group;lactate dehydrogenase activity increased first and then decreased.The2.85-8.81 mg/kg group was significantly higher than the control group（P<0.05）;the1.83-30.64 mg/kg group was significantly higher in alanine aminotransferase activity than the control group（P<0.05）;the content of liver vitamin B₁ increased at first and then stabilized,which was significantly higher in the 4.72-30.64 mg/kg group than in the 0.87-2.85 mg/kg group（P<0.05）.3)The serum glucose content decreased first and then increased,the 2.85-30.64 mg/kg group was significantly lower than the control group and the 1.83 mg/kg group（P<0.05）,the 4.72 mg/kg group had the lowest value.A broken-line regression analysis of the liver transketolase activity and liver vitamin B₁ content parameters showed that the dietary vitamin B₁requirement of juvenile rockfish with a body weight of 36 g was 3.29 to 5.61 mg/kg.Part2:This experiment investigated the effects of dietary vitamin B₆ content on growth performance,body composition,liver enzyme activities,serum biochemistry 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,1)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）.2)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.3)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）.4)In serum,the glucose content of the 4.16,6.32 mg/kg group was significantly lower than the control group（P<0.05）;the triglyceride of the 3.25-31.14 mg/kg group was significantly lower than the control group（P<0.05）;The high-density lipoprotein cholesterol（HDL-C）of the 3.25-31.14mg/kg group was significantly higher than that of the control group（P<0.05）;the aspartate aminotransferase showed an upward trend,and the control group had the lowest value,The difference was not significant in the 6.32-31.14 mg/kg group（P>0.05）;the alanine aminotransferase in the 6.32-31.14 mg/kg group was significantly higher than that in the control group（P<0.05）.5)The relative expression level of GOT1 and GOT2 genes increased at first and then decreased,with the 3.25 to31.14 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 4.16to 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 B₆requirement of juvenile rockfish with a body weight of 36 g was 3.52 to 6.32 mg/kg.Part3:The juvenile rockfish（Sebastes schlegeli）were fed with dietary containing different concentrations of vitamin B₆ in this study.The composition and abundance of intestinal microbial communities in juvenile rockfish were analyzed by using high-throughput sequencing technology.Meanwhile,the activity of digestive enzymes in the gastrointestinal were measured.Furthermore,the effect of vitamin B₆ content on the gastrointestinal digestibility and intestinal flora of juvenile rockfish will be obtained.The experiment were divided into six groups（n=3/group）as follows:A,B,C,D,E,and F（the actual content of vitamin B₆ in each group was 2.08,3.25,4.16,6.32,10.17,and 31.14 mg/kg）.A total of 1241940 effective sequences were obtained by sequencing,which can be classified into 1649 classification operation units（OTUs）.Proteobacteria dominate the intestinal community distribution at the level of the phylum,followed by Bacteroidetes,Patescibacteria,Firmicutes and so on.The dominant bacterias include Brevundimonas,Limnobacter,Pseudomonas and so on.Pepsin,trypsin,and lipase showed a trend of rising first and then falling with the increase of vitamin B₆ contents.The activity of pepsin in the C-F group were significantly higher than A and B groups（P<0.05）.The activity of pepsin in the D group was the highest.The activity of trypsin and lipase in B-F groups were significantly higher than the group A（P<0.05）.Some intestinal flora（Brevimonas,Pseudomonas and so on）can produce digestive enzymes such as protease,lipase.The concentrations of the digestive enzymes were increased with the increased of vitamin B₆ contents,therefore,the digestion and absorption ability of the intestine were increased,and the nutritional metabolism of the juveniles was promoted.