枯草芽孢杆菌对吉富罗非鱼幼鱼生长性能、血清生化指标、抗氧化能力及脂质代谢的影响OACHSSCD

[Objective]To investigate the mechanism by which dietary supplementation with Bacillus subtilis improves the health of Nile tilapia(Oreochromis niloticus).[Method]Juvenile GIFT tilapia with an initial body mass of(16.17±1.32)g were used as experimental subjects.Six iso-nitrogenous and iso-lipidic experimental diets were formulated.The basal diet served as the control group(0 CFU/kg supplementation),while the other five experimental diets were supplemented with Bacillus subtilis at doses of 1×107,1×108,1×109,1×1010,and 1×1011CFU/kg,respectively.After 60 days of feeding,growth performance,digestive enzyme activities,serum biochemical indices,antioxidant enzyme activities,and the expression levels of lipid metabolism-related genes were determined in each group.[Result]Compared with the control group,the mass gain rate,specific growth rate,and daily growth index of tilapia in all groups were significantly increased(P<0.05),while the feed conversion ratio was significantly decreased(P<0.05).The activities of intestinal trypsin,lipase,and amylase were significantly enhanced(P<0.05).The activities of superoxide dismutase,catalase,glutathione peroxidase,and total antioxidant capacity in serum and liver were significantly increased(P<0.05),while the malondialdehyde content was significantly decreased(P<0.05).The contents(activities)of low-density lipoprotein,triglyceride,lactate dehydrogenase,aspartate aminotransferase,and alanine aminotransferase were significantly decreased(P<0.05),while glucose and high-density lipoprotein contents were significantly increased(P<0.05).Among lipid metabolism-related genes,the expression levels of peroxisome proliferator-activated receptor α,peroxisome proliferator-activated receptor β,acetyl-CoA carboxylase,mammalian target of rapamycin,stearoyl-CoA desaturase,carnitine palmitoyl transferase,adenosine monophosphate-activated protein kinase,phosphatidylinositol 3-kinase,protein kinase B,and peroxisome proliferator-activated receptor gamma coactivator 1α were significantly up-regulated(P<0.05),while the expression levels of peroxisome proliferator-activated receptor γ,sterol regulatory element-binding protein,fatty acid synthase,hormone-sensitive lipase,glucose-6-phosphate dehydrogenase,ribosomal protein S6 kinase,and lipoprotein lipase were significantly down-regulated(P<0.05).[Conclusion]Dietary supplementation with B.subtilis can significantly improve the growth performance of juvenile GIFT Tilapia by enhancing digestive enzyme activities,strengthening antioxidant capacity,and regulating the expression of lipid metabolism-related genes.The optimal supplementation dose was 1×109 CFU/kg,which could be used as a green feed additive in healthy tilapia aquaculture.