【作者】 石磊；

【导师】 冯琳； 周小秋；

【作者基本信息】 四川农业大学 ， 动物营养与饲料科学， 2015， 硕士

【摘要】 本试验旨在研究饲粮添加不同水平叶酸对生长中期草鱼生长性能、肠道免疫能力、紧密连接和抗氧化能力的影响及其作用机制。将初始体重为267.69±0.87 g的体格均匀、健康的草鱼随机分配到18个网箱中,设置6个叶酸水平,各组间初始体重差异不显著(P>0.05),进行8周的动物实验,实验期间各处理分别投喂叶酸含量为0.10(对照组)、0.47、1.03、1.48、1.88和3.12mg/kg的饲粮。本研究结果显示：饲粮中适宜水平的叶酸显著提高中期草鱼的末重、增重百分比(PWG)、特异性增长率、摄食量和饲料效率(P<0.05)。适宜水平叶酸显著提高草鱼肠道胰蛋白酶、糜蛋白酶、脂肪酶、淀粉酶活性、Na+/K+-ATP酶、碱性磷酸酶、肌酸激酶(CK)和γ-谷氨酰转移酶活性(P<0.05),同时,适宜水平叶酸上调前肠、中肠和后肠CK和Na+/K+-ATPase alpha subunit isoform 1基因表达(P<0.05),但是对肠道Na+/K+-ATPase alpha subunit isoform 8基因表达无影响(P>0.05)。进一步研究发现,适宜水平叶酸上调肠道雷帕霉素靶蛋白和S6蛋白激酶1基因表达,但是下调草鱼肠道e1F4E结合蛋白基因表达(P<0.05)。此外,适宜水平叶酸显著增加草鱼肠道酸性磷酸酶和溶菌酶活性以及补体C3的含量；显著下调草鱼肠道促炎细胞因子白介素1β、白介素8、肿瘤坏死因子α、信号分子核因子κBp65、IκB激酶(IKK) α、 IKK-β和IKK-γ的基因表达(P<0.05)；显著上调肠道抗炎细胞因子白介素10、转化生长因子β和核因子κB抑制蛋白(IκB)的基因表达(P<0.05)。同时,适宜水平叶酸显著上调occludin、ZO-1和claudin-b在草鱼肠道的基因表达(P<0.05),显著下调claudin-15、肌球蛋白轻链激酶和p38丝裂原活化蛋白激酶在草鱼肠道的基因表达(P<0.05)。同时本试验研究发现,适宜水平叶酸降低草鱼肠道的氧自由基、丙二醛和蛋白羰基的含量(P<0.05),显著增加肠道还原型谷胱甘肽的含量以及铜锌超氧化物歧化酶(Cu/ZnSOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GPx)、谷胱甘肽硫转移酶(GST)和谷胱甘肽还原酶(GR)的活性,显著降低肠道锰超氧化物歧化酶(MnSOD)活性(P<0.05)。进一步研究发现,适宜水平叶酸显著上调草鱼肠道Cu/ZnSOD、CAT、GPx、GST、GR和核因子相关因子2基因表达,下调肠道MnSOD. Kelch样ECH联合蛋白1a (Keap1a)和Keap1b基因表达(P<0.05)。在本试验条件下,以PWG为标识,确定中期草鱼(267-747 g)饲粮的叶酸需要量为1.60mg/kg饲粮。更多还原

【Abstract】 To investigate the effects of dietary folic acid on fish growth performance, immunity, tight junctions and antioxidant capacity, as well as the potential mechanism, young grass carp (Ctenopharyngodon idelld) (267.69 ± 0.87 g) were fed diets containing graded levels of folic acid at 0.10 (basal diet),0.47,1.03,1.48,1.88 and 3.12 mg/kg diet for 8 weeks.Data showed that percent weight gain (PWG), specific growth rate, feed intake and feed efficiency were increased with folic acid up to optimum level (P< 0.05). Optimum folic acid increased intestinal trypsin, chymotrypsin, lipase, amylase, alkaline phosphatase, Na+/K+-ATPase, γ-glutamyl transpeptidase and creatine kinase (CK) activities (P< 0.05). Furthermore, optimum folic acid up-regulated intestinal CK and Na+/K+-ATPase alpha subunit isoform 1 mRNA levels (P< 0.05). However, folic acid had no effect on Na+/K+-ATPase alpha subunit isoform 8 mRNA levels in grass carp intestine (P> 0.05). Moreover, optimum folic acid up-regulated target of rapamycin (TOR) and S6 kinase 1 mRNA levels, and down-regulated eIF4E-binding protein mRNA levels in fish intestine (P < 0.05). Optimum folic acid increased acid phosphatase, lysozgme and complement C3 in the intestine of young grass carp (P< 0.05). Furthermore, optimum folic acid down-regulated interleukin 1β, interleukin 8, tumor necrosis factor α, nuclear factor κB p65, IκB kinase α(IKK-α), KK-β and IKK-γ mRNA levels and up-regulated interleukin 10, transforming growth factor β and inhibitor of κB mRNA levels in the intestine of young grass carp (P< 0.05). Our study also presented that moderate folic acid up-regulated occludin, ZO-1 and claudin-b mRNA levels in the intestine of grass carp (P< 0.05). Furthermore, optimal folic acid up-regulated claudin-15, MLCK and p38 MAPK mRNA levels in the intestine of grass carp (P< 0.05). Data from this study showed that ROS, MDA and PC contents were decreased by moderate folic acid in whole intestine (P< 0.05). In addition, the increase of Cu/ZnSOD, CAT, GPx, GST and GR activities, and the decrease of MnSOD activity may be due to that optimal folic acid up-regulated Cu/ZnSOD, CAT, GPx, GST and GR mRNA levels, and down-regulated MnSOD mRNA level in intestine (P< 0.05). Furthermore, optimal folic acid up-regulated NF-E2-related factor 2 mRNA level, whereas down-regulated both Keapla and Keaplb mRNA levels in intestine (P< 0.05). Additionally, in this study, base on PWG, the requirement of young grass carp (267-747 g) for folic acid was 1.60 mg/kg diet.更多还原