| 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 ?g/mL;The MIC of C8 for E.coli,Salmonella and Staphylococcus aureus were 2000 ?g/mL,2000 ?g/mL and 1000 ?g/mL;The MIC of C10 for E.coli,Salmonella and Staphylococcus aureus were 2000 ?g/mL,4000 ?g/mL and 1000 ?g/mL;The MIC of C12 for E.coli,Salmonella and Stphylococcus aureus were 2000 ?g/mL,4000 ?g/mL and 1000 ?g/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(???:experimental group)were fed the basal diet supplement with 2?4 and 8 g/kg of MCFA,respectively,and the ? group was fed the basal diet supplement with 25 g/kg of MCT.The result showed that:Compared with the group ?,in 1?21 d,the ADFI and ADG of group ??? had the tendency to decrease,but the differences were not significant(P>0.05);Compared with group ? and ?,in 21-42d,the ADFI of group ? 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 ? was significantly lower than group ? and ?(P<0.05),the F/G of group ? 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 ?,the TP of group ??? 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 ? was significantly lower than group ?,? and ?(P<0.05),among other groups there were no significant differences on the content of TG(P>0.05);The TCH of group ? was significantly higher than the other groups(P<0.05);The ALP of group ?and ? 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 ?and ? were significantly higher than the other groups(P<0.05);There were no significant differences of TNF-? among each group(P>0.05).The villus height of group ? and ? was significantly higher than group ? and ? 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 ? 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 ? and ? in ileum were significantly higher than group ?(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 ? was significantly lower than group ? and ? 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 ? 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 ? in ileum was significantly higher than group ?,? and ?(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 ? and ? were significantly lower than the gastric pH of group ? and ?(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 ?,? and ? were significantly lower than the ileum pH of group ?(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. |
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