| Biotin and pantothenic acid are essential water-soluble vitamin for fish.Biotin acts both in gluconeogenesis and fatty acid synthesis pathways as a coenzyme for several CO2 fixing enzymes.Pantothenic acid participates in numerous intermediary metabolic reactions as a component of coenzyme A,which plays a crucial role in reactions which glucose,fatty acids and amino acids enter into energy-yielding tricarboxylic acid cycle,acetylation of choline to from the neurotransmitter acetylcholine and biosynthesis of fatty acids.As aquaculture industry develops rapidly,nutritional diseases occur frequently during fish farming,thus do great harm to the development of efficient and sustainable aquaculture.Bearing these in mind,the present study was conducted to estimate the optimal dietary biotin and pantothenic acid requirement of juvenile blunt snout bream(Megalobrama amblycephala),an economically important herbivorous freshwater fish widely cultured in China.In addition,the potential regulatory effects of dietary biotin and pantothenic acid on the intestinal enzymes activities,anti-oxidant status and fatty acid metabolism of fish were also investigated.1 Optimal dietary biotin requirement of juvenile blunt snout bream,Megalobrama amblycephalaThis study was conducted to determine the optimal dietary biotin requirement of juvenile Megalobrama amblycephala.Quadruple groups of fish(initial average weight 2.01±0.01 g)were fed thrice daily with six isonitrogenous and isoenergetic purified diets containing 0(basal diet),0.02,0.05,0.16,0.62 and 2.49 mg/kg biotin,respectively,for 8 weeks.Results showed that survival rate,final weight,specific growth rate,protein efficiency ratio and nitrogen retention efficiency all increased significantly(P<0.01)as dietary biotin levels increased from 0 mg/kg to 0.05 mg/kg,whereas the opposite was true for feed conversion ratio.Dressout percentage,condition factor,hepatosomatic index,viscera/body ratio all showed no significant differences(P>0.05)within the biotin range tested.Contrary to moisture content,whole-body protein and lipid contents showed a positive correlation with dietary biotin levels.In addition,liver biotin content increased significantly(P<0.05)with increasing dietary biotin levels up to 0.62 mg/kg and then plateaued.Hepatic pyruvate carboxylase and acetyl CoA carboxylase activities both showed an increasing trend as dietary biotin levels increased.Based on the regression analysis of weight gain,liver biotin concentration,hepatic pyruvate carboxylase and acetyl CoA carboxylase activities,the optimal dietary biotin requirement of juvenile Megalobrama amblycephala is estimated to be 0.06-0.08 mg/kg,respectively.2 Effects of dietary biotin on carcass composition,intestinal function and antioxidant status of juvenile blunt snout bream,Megalobrama amblycephalaQuadruple groups of blunt snout bream(Megalobrama amblycephala)(initial average weight 2.01±0.01g)were fed thrice daily with six isonitrogenous and isoenergetic purified diets containing 0(basal diet),0.02,0.05,0.16,0.62 and 2.49 mg/kg biotin,for 9 weeks respectively.Results showed that intestinal lipase and protease activities increased initially and then decreased slightly with the dietary biotin levels increased from 0 to 2.49 mg/kg,the maxima were reached at 0.62 mg/kg and 0.16 mg/kg,respectively.Fish fed the diet with biotin 0.16 mg/kg had lower carcass moisture content and higher carcass crude lipid and crude protein contents than those fed basal diets,the differences were significant(P<0.05).GSH,GPX and t-SOD increased significantly(P<0.05)as dietary biotin levels increased from 0 mg/kg to 0.05 mg/kg and then had plateaued.Results indicated that appropriate dietary biotin can improve intestinal lipase and protease activities,carcass lipid and crude protein content and hepatic antioxidant capacity of juvenile blunt snout bream.3 Optimal dietary pantothenic acid requirement of juvenile blunt snout bream,Megalobrama amblycephalaFour groups of juvenile blunt snout bream Megalobrama amblycephala(initial average weight 6.04±0.02 g)were fed three times daily with six semi-purified diets containing 3.39(PA unsupplied diet),10.54,19.28,31.04,48.38 and 59.72 mg/kg calcium D-pantothenate for 8 weeks.The results showed that survival rate,final weight,specific growth rate,protein efficiency ratio,nitrogen retention efficiency and condition factor all increased significantly(P<0.01)as dietary PA levels increased from 3.39 mg/kg to 19.28 mg/kg,whereas the opposite was true for feed conversion ratio.No significant differences were found in fish treated with varies PA levels(P>0.05).Whole-body crude protein increased as dietary PA levels increased,while the opposite pattern was found for the crude lipid content.The liver PA concentration and coenzyme A content rose significantly(P<0.01),up to 31.04 mg/kg,with increasing dietary PA levels and then plateaued.Based on broken-line regression analyses of weight gain,liver CoA concentrations and PA contents against dietary PA levels,the optimal dietary PA requirements of juvenile blunt snout bream were estimated to be 23.91-25.68 mg/kg.4 Effects of dietary pantothenic acid on intestinal function,antioxidant status and fatty acid synthesis of juvenile blunt snout bream,Megalobrama amblycephalaFour groups of juvenile blunt snout bream Megalobrama amblycephala(initial average weight 6.04±0.02 g)were fed three times daily with six semi-purified diets containing 3.39(PA unsupplied diet),10.54,19.28,31.04,48.38 and 59.72 mg/kg calcium D-pantothenate for 8 weeks.The results showed that intestinal a-amylase,lipase,protease,Na+-K+-ATPase,alkaline phosphatase and gamma-glutamyl transferase activities were all elevated in fish fed PA-supplemented diets.Hepatic catalase activities improved with increases in dietary PA,while the opposite was true for malondialdehyde contents.The percentage of hepatic saturated fatty acids increased significantly(P<0.01)as dietary PA levels increased,while the percentages of monounsaturated fatty acids and polyunsaturated fatty acid(PUFA)decreased as dietary PA increased.Fish fed diets containing 19.28 and 31.04 mg/kg PA exhibited higher(P<0.01)docosahexaenoic acid and PUFA percentages in muscle than those fed with other diets.The expression of the gene encoding pantothenate kinase was significantly up-regulated(P<0.01)in fish fed PA-supplemented diets.Hepatic Acetyl-CoA carboxylase a,fatty acid synthetase,stearoyl regulatory element-binding protein 1 and liver X receptor a genes all increased significantly(P<0.01)as dietary PA levels increased from 3.39 mg/kg to 31.04 mg/kg.Results indicated that appropriate dietary PA can improve intestinal absorptive and diegestive enzymes activities,antioxidant enzymes activities and fatty acid synthesis genes of juvenile blunt snout bream.5 Effects of dietary biotin supplementation on growth performance,lipid status and mRNA expression of fatty acids metabolism regulatory genes in blunt snout bream Megalobrama amblycephala fed high-fat dietA 2×2 factorial design was conducted to elucidated the effects of dietary biotin on growth and lipid synthesis in blunt snout bream,Megalobrama amblycephala fed high-fat diets.Fish were fed three times daily with four experimental diets containing two lipid levels(5%and 11%)and two biotin supplementation levels(0.06 mg/kg and 2.50 mg/kg)for 8 weeks.The results showed that fish fed with diets contained 5%lipid had a significant(P<0.05)higher specific growth rate than those fed with 11%lipid content diets.The opposite was true for whole-body lipid content,liver lipid content,IPF ratio,liver and muscle total triacylglycerol concentration and muscle total cholesterol content.A significant(P<0.05)increment in liver saturated fatty acids,C18 polyunsaturated fatty acids,eicosapentaenoic acid and docosahexaenoic acid content was found in fish fed with 2.50 mg/kg biotin supplementation diets.Hepatic Acetyl-CoA carboxylase α(ACCa),fatty acid synthetase,stearoyl regulatory element-binding protein 1(SREBP1)and liver X receptor a genes expression was significantly(P<0.05)elevated in fish fed with 5%lipid content diets supplemented with biotin than those fed with lower biotin levels at the same lipid content level.Significant(P<0.01)interaction effects was observed in fish fed with lipid and biotin supply on hepatic ACCa and SREBP1 expression.The expression of peroxisome proliferatoractivated receptor a(PPARa),carnitine palmitoyltransferase I genes showed a significant(P<0.05)decline in fish fed with high-fat diets,while neither biotin supplementation nor interaction effect(P>0.05)was found in fish on those two genes expression.Liver acyl-CoA oxidase(ACO)expression evaluated significantly(P<0.05)with the biotin supplementation increasing from 0.06 mg/kg to 2.50 mg/kg.There was a significant(P<0.05)interaction effect between dietary lipid and biotin supplementation in hepatic ACO and fatty acyl-CoA synthetase genes expression.6 Effects of dietary pantothenic acid supplementation on growth performance,fatty acid metabolism and antioxidant status in blunt snout bream Megalobrama amblycephala fed high-fat dietThis study used a.2×2 factorial design to elucidated the effects of dietary pantothenic acid on growth,fatty acid metabolism and antioxidant status in juvenile blunt snout bream,Megalobrama amblycephala fed high-fat diets.Fish were fed three times daily with four experimental diets containing two lipid levels(5%and 11%)and two pantothenic acid supplementation levels(24 mg/kg and 240 mg/kg)for 8 weeks.After the feeding trial,specific growth rate,mesenteric fat index,whole-body lipid content,liver and muscle total lipid content,triacylglycerol and cholesterol levels increased significantly(P<0.05)as the dietary lipid increasing from 5%to 11%,as well as hepatic saturated fatty acids and polyunsaturated fatty acids contents,whereas muscle EPA and DHA content decreased significantly(P<0.05)as the PA supplementation increasing from 24 mg/kg to 240 mg/kg.A significant(P<0.05)interaction effect was observed between dietary lipid and pantothenic acid supplementation on liver C18:3n-6,muscle C18:3n-6,eicosapentaenoic acid and docosahexaenoic acid.Hepatic total superoxide dismutase,catalase and glutathione peroxidase activities,malondialdehyde concentration,Mitochondrial protein and cytochrome c are all significantly(P<0.05)increased as the dietary lipid level increasing from 5%to 11%,while a reduced tendency showed as the dietary pantothenic acid supplementation increasing.The opposite was true for liver glutathione and cytosolic cytochrome c concentration.Fish fed high-fat diets showed significant lower(P<0.05)mitochondrial ND1 and ATP6 gene expression than those fed with low-fat diets.Among the groups treated with high fat level,dietary PA has a significant(P<0.01)positive correlation on the ND1 expression.Mitochondrial COX2 gene expression was markedly up-regulated(P<0.05)as the dietary PA supplementation increasing.Results indicated that dietary PA may improve growth,antioxidant capacity and mitochondrial function in juvenile blunt snout bream fed with high-fat diets by enhancing the antioxidant enzymes activities and mitochondrial respiration chain genes expression,as well as reducing muscle PUFA accumulation. |
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