【作者】 陈晨；

【导师】 徐子伟； 王恬；

【作者基本信息】 南京农业大学 ， 动物营养与饲料科学， 2015， 硕士

【摘要】 本研究分为两个部分,即MCFA体外抑菌试验和体内添加试验,为在仔猪日粮中应用不同水平的MCFA提供试验依据。第一部分,MCFA对于不同细菌的体外抑制试验。本试验选用四种MCFA,分别为己酸(6C:0)、辛酸(8C:0)、癸酸(10C:0)和月桂酸(12C:0)作为抗菌剂,选取三种细菌,分别为大肠杆菌、沙门氏菌以及金黄色葡萄球菌作为试验对象。采用MIC测定试验和正交试验,通过正交最优理论以及验证试验,最后得到一个脂肪酸最佳抑菌组合。试验结果表明:1、己酸的抑菌能力最强,且对三种供试菌株都有很强的抑制作用,而辛酸、癸酸和月桂酸的抑菌能力都比较弱,尤其是对沙门氏菌几乎没有抑制作用。相对于大肠杆菌和沙门氏菌,四种MCFA都对金黄色葡萄球菌表现出更强的抑制作用。2、己酸对大肠杆菌、沙门氏菌和金黄色葡萄球菌的MIC都为10000μg/mL;辛酸对大肠杆菌、沙门氏菌和金黄色葡萄球菌的MIC分别为2000μg/mL、2000 μg/mL和1000μg/mL;癸酸对大肠杆菌、沙门氏菌和金黄色葡萄球菌的MIC分别为2000 μg/mL、4000μg/mL和1000 μg/mL;月桂酸对大肠杆菌、沙门氏菌和金黄色葡萄球菌的MIC分别为 2000 μg/mL、4000 μg/mL和 1000 μg/mL。3、4种脂肪酸对大肠杆菌的影响大小为:己酸>癸酸>辛酸>月桂酸,4种脂肪酸的对大肠杆菌的最佳抑菌比例为己酸:辛酸:癸酸:月桂酸=4:2:1:1;对沙门氏菌的影响大小为:己酸>辛酸>月桂酸>癸酸,对沙门氏菌的最佳抑菌比例为己酸:辛酸:癸酸:月桂酸=1:2:4:1;对金黄色葡萄球菌的影响大小为:辛酸>己酸>月桂酸>癸酸,对金黄色葡萄球菌最佳抑菌比例为己酸:辛酸:癸酸:月桂酸=2:2:4:1。4、与己酸相比,3种脂肪酸最优组合对于大肠杆菌、沙门氏菌和金黄色葡萄球菌的抑制效果都更强,其中又以己酸:辛酸:癸酸:月桂酸=1:2:4:1这个组合的抑制率最大,故选为最佳抑菌组合。第二部分,饲粮中添加不同水平的MCFA对于断奶仔猪的影响。本试验以200头23日龄的健康断奶仔猪为研究对象,被随机分为5组,每组四个重复,每个重复10头。饲喂以下5种日粮:Ⅰ组(对照组)基础日粮;Ⅱ～Ⅳ组基础日粮添加0.2%、0.4%和0.8%的MCFA;V组基础日粮加2.5%的MCT产品,试验为期42d,主要测定其对断奶仔猪生产性能、肠粘膜形态的影响,分析胃肠道中pH的变化情况,肠道各段大肠杆菌、乳酸菌以及菌群结构的消长规律,考察MCFA在保护断奶仔猪肠上皮结构完整性方面的作用。试验结果表明:1、与Ⅰ组相比,在1～21d,Ⅱ～Ⅴ组ADFI和ADG有降低的趋势,但差异不显著(P>0.05);在试验第21～42d,V组的ADFI较Ⅰ和Ⅱ组显著下降(P<0.05),其余各组间差异不大(P>0.05);在1～42d,V组的ADFI较Ⅰ和Ⅱ组显著下降(P<0.05),Ⅲ组的F/G显著低于Ⅴ组(P<0.05),其余各组间差异不大(P>0.05)。2、相比Ⅰ组,Ⅱ-Ⅴ组TP含量显著提高(P<0.05),但各组之间GLO含量差异不显著(P>0.05);Ⅳ组的TG含量低于Ⅰ组、Ⅱ组和Ⅴ组(P<0.05),其余各组之间TG含量无明显差异(P>0.05);Ⅰ组的TCH含量显著高于其它组(P<0.05);Ⅲ组和Ⅳ组的ALP含量显著低于其余各组(P<0.05);各组之间AST含量差异不显著(P>0.05),Ⅲ组和Ⅴ组的ALT含量显著高于其余各组(P<0.05);TNF-α含量各组之间无显著差异(P>0.05)。3、Ⅱ组和Ⅳ组十二指肠绒毛高度显著高于Ⅰ组和Ⅲ组(P<0.05),各组之间十二指肠隐窝深度差异不显著(P>0.05);Ⅲ组空肠隐窝深度显著高于其它组(P<0.05),各组之间空肠绒毛高度差异不显著(P>0.05);Ⅱ组和Ⅲ组回肠绒毛高度显著高于Ⅰ组(P<0.05),各组之间回肠隐窝深度差异不显著(P>0.05)。4、Ⅱ组十二指肠的IEL数量显著低于Ⅰ组、Ⅲ组和Ⅳ组(P<0.05),其余各组间十二指肠的IEL数量差异不显著(P>0.05);Ⅲ组空肠的IEL数量显著高于Ⅳ组(P<0.05),其余各组间空肠的IEL数量差异不显著(P>0.05);试验Ⅱ组回肠的IEL数量显著高于Ⅰ组、Ⅲ组和Ⅳ组(P<0.05),其余各组间回肠的IEL数量差异不显著(P>0.05)。5、Ⅱ组和Ⅳ组的胃pH值显著低于Ⅰ组和Ⅲ组(P<0.05),其余各组间的胃pH值差异不显著(P>0.05);相对于Ⅰ组,Ⅱ组、Ⅲ组和Ⅳ组的回肠pH值都显著降低(P<0.05)。各组肠道菌群的数量差异不显著(P>0.05)。综合上述试验,得出结论:经过体外抑菌试验和动物试验表明,MCFA具有明显的体外抑菌效果,对于断奶仔猪生长作用不明显,可以显著提高小肠绒毛高度,降低胃肠道pH值,但对于肠道肠道微生物的影响比较轻微。更多还原

【Abstract】 The study was divided into two parts which included antibacterial tests of MCFA in vitro and animal experiments in vivo,and this study provided the experimental basis for applying different levels of MCFA in piglets.Experiment 1:The aim of this experiment was to evaluate the inhibition effect of MCFA for different bacteria in vitro.We selected four kinds of MCFA,including caproic(C6:0),caprylic(C8:0),capric(C10:0)and lauric acid(C12:0),and three kinds of bacteria,such as E.coli,Salmonella and Staphylococcus aureus.We used the orthogonal trial design and the test of MIC to obtain an optimal antibacterial combination of fatty acids.The result showed that:the inhibitory ability of C6 was greater than the other acids,and the inhibition of C8,C10 and C12 were different for various bacteria.For three kinds of bacteria,the inhibitory capacity of MCFA to Staphylococcus aureus was stronger than E.coli and Salmonella.The MIC of C6 for every bacteria was 1000 μg/mL;The MIC of C8 for E.coli,Salmonella and Staphylococcus aureus were 2000 μg/mL,2000 μg/mL and 1000 μg/mL;The MIC of C10 for E.coli,Salmonella and Staphylococcus aureus were 2000 μg/mL,4000 μg/mL and 1000 μg/mL;The MIC of C12 for E.coli,Salmonella and Stphylococcus aureus were 2000 μg/mL,4000 μg/mL and 1000 μg/mL.The influence of MCFA on E.coli was:C6>C10>C8>C12,and the optimal antibacterial combination was that C6:C8:C10:C12 =4:2:1:1.The influence of MCFA on Salmonella was:C6>C10>C8>C12,and the optimal antibacterial combination was that C6:C8:C10:C12 =1:2:4:1.The influence of MCFA on Staphylococcus aureus was:C8>C6>C12>CIO,and the optimal antibacterial combination was that C6:C8:C10:C12 =2:2:4:1.Compared with the caproic,the effects of three optimal combinations for E.coli,Salmonella and Staphylococcus aureus were more effective.And the effect of the combination(C6:C8:C10:C12 = 1:2:4:1)was best.So the optimal antibacterial combination was it.Experiment 2:This experiment was to study the effect of different levels MCFA on production performance,intestinal microbial flora and mucosa morphology in weaning piglets.200 weaning piglets aged 23d were randomly divided into five groups with four replicates per group and ten piglets per repeat.The experiment lasted for 42 days.Piglets were fed five sectors of diets,including a basal diet(I:control group),and the other groups(Ⅱ～Ⅳ:experimental group)were fed the basal diet supplement with 2、4 and 8 g/kg of MCFA,respectively,and the Ⅴ group was fed the basal diet supplement with 25 g/kg of MCT.The result showed that:Compared with the group Ⅰ,in 1～21 d,the ADFI and ADG of group Ⅱ～Ⅴ had the tendency to decrease,but the differences were not significant(P>0.05);Compared with group Ⅰ and Ⅱ,in 21-42d,the ADFI of group Ⅴ was significantly decreased(P<0.05),and there were no significant differences among the other groups(P>0.05);In 1～42d,the ADFI of group Ⅴ was significantly lower than group Ⅰ and Ⅱ(P<0.05),the F/G of group Ⅲ group was significantly lower than group V(P<0.05),and there was no significant difference among the other groups(P>0.05).Compared to Group Ⅰ,the TP of group Ⅱ～Ⅴ were significantly increased(P<0.05),and there were no significant differences on the content of GLO among each group(P>0.05);The TG of the group Ⅳ was significantly lower than group Ⅰ,Ⅱ and Ⅴ(P<0.05),among other groups there were no significant differences on the content of TG(P>0.05);The TCH of group Ⅰ was significantly higher than the other groups(P<0.05);The ALP of group Ⅲand Ⅳ were significantly lower than the other groups(P<0.05);There were no significant differences on the content of AST among each group(P>0.05),and the ALT of group Ⅲand Ⅴ were significantly higher than the other groups(P<0.05);There were no significant differences of TNF-α among each group(P>0.05).The villus height of group Ⅱ and Ⅳ was significantly higher than group Ⅰ and Ⅲ in duodenum(P<0.05),and there were no significant differences on the crypt depth among each group in duodenum(P>0.05);The crypt depth of group Ⅲ was significantly higher than the other groups in jejunum(P<0.05),and there were no significant differences on the villus height among each group in jejunum(P>0.05);The villus height of group Ⅱ and Ⅲ in ileum were significantly higher than group Ⅰ(P<0.05),and there were no significant differences on the crypt depth among each group in ileum(P>0.05).The number of IEL of group Ⅱ was significantly lower than group Ⅲ and Ⅳ in duodenum(P<0.05),and there were no significant differences on the number of IEL between the other groups in duodenum(P>0.05);The number of IEL of group Ⅲ in jejunum was significantly higher than group IV(P<0.05),and there were no significant differences on the number of IEL between the other groups in jejunum(P>0.05);The number of IEL for group Ⅱ in ileum was significantly higher than group Ⅰ,Ⅲ and Ⅳ(P<0.05),and there were no significant differences on the number of IEL between the other groups in ileum(P>0.05).The gastric pH of group Ⅱ and Ⅳ were significantly lower than the gastric pH of group Ⅰ and Ⅲ(P<0.05),and there were no significant differences on the gastric pH between the other groups(P>0.05);The ileum pH of group Ⅱ,Ⅲ and Ⅳ were significantly lower than the ileum pH of group Ⅰ(P<0.05).There were no significant differences on the quantity of intestinal flora among the other groups(P>0.05).In conclusion,after antibacterial tests in vitro and animal experiments in vivo,it showed that MCFA had significant antibacterial effects in vitro,and MCFA could significantly improve the villus height and reduce gastrointestinal pH values,but no significant effects on the intestinal gut bacterias for weaned piglets.更多还原