| The present experiment investigated the effects of dissolved oxygen content and dietary lipid level on growth performance,serum and liver biochemical index,liver histology,fatty acid composition,lipid metabolism-related genes expression of Procypris merus,and to investigate whether increasing the lipid level in feed can alleviate or improve the effect of hypoxic environment on the hypoxic environment of P.merus.The experiment was carried out with 3 × 3two-factor experiment design,with the dissolved oxygen content of 1mg/L,3mg/L and 5mg /L,and the dietary lipid levels corresponding to each dissolved oxygen content were 3.15%,7.21% and 11.44%,respectively.The experiment was divided into 9 groups,and 3 replicates were set for each group.The following conclusions are drawn:1.In terms of growth performance,both dissolved oxygen content and dietary lipid level had a significant effect on the growth of P.merus.Within the scope of this experiment,the higher dissolved oxygen content and dietary lipid level were,the better the growth of P.merus.2.In terms of nutrient composition,high dietary lipid level is not conducive to protein transformation and protein accumulation in fish.Hypoxia can cause oxidative stress in fish,resulting in fat accumulation and fatty liver formation in severe cases.3.When the dissolved oxygen content was 1mg/L,ALT and AST contents increased with the dietary lipid level,showing a tendency of decreasing first and then increasing.It was speculated that under the influence of the dietary lipid level,the oxidative stress caused by hypoxic conditions on the liver was improved.4.In terms of antioxidant capacity,the variation trend of antioxidant index in serum and liver is different,which may be because different tissues have different ability to cope with oxidative stress.Moreover,the influence on serum antioxidant capacity is dominated by dissolved oxygen content,while the influence on liver antioxidant capacity is dominated by dietary lipid level.5.On the effect of liver tissue structure,Hypoxia and too high dietary lipid level can cause the liver fatty liver disease symptoms,but the degree is different.Hypoxia is due to oxidative damage to liver tissues caused by oxidative stress,while high fat diet is due to excess nutrients and the body cannot be completely metabolized.It was also found that in the hypoxic group,the section observation results of the dietary lipid addition level of 7.21% group were healthier than that of 3.15% group.It was speculated that the higher lipid level alleviated the damage caused by hypoxic stress.6.On the influence of fat metabolism related genes,high dissolved oxygen content can promote the expression of liver LXR gene,which in turn affects the fat synthesis in fish by regulating the expression of lipid genes.The accumulation of fat in fish caused by low oxygen stress or high dietary lipid level will control the balance of lipid metabolism in fish by inducing the production of LPL gene.7.The effects on fatty acid composition of liver,improved dissolved oxygen content and more lipid level in dietary made PUFA more easily obtained by P.merus.When PUFA content obtained from dietary can meet their own needs,LNA is no longer used to synthesize essential fatty acids such as EPA and DHA,but its content accumulates in fish and increases. |
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