Use Of Feed Oil To Control Escherichia Coli O157:H7 In Cattle

The aim of current research was to study the feasibility of using feed oil to eliminate the infection of Escherichia coli O157:H7 in cattle. The whole experiment was carried out by two trails. In first trail, the ruminal and abomasal content were sampled from cattle fed different diet with or without flaxseed and were used to do the in vitro culture with Escherichia coli O157:H7 to see the influence of feed oil on the pathogen. At the same time we analyzed the composition of the fatty acids and the concentration of the IgA in bovine gastro-intestinal content to see the influence of feed oil on the bovine intestinal immunity. In the second trail, we studied the antibacterial effect of different single fatty acid on E.coli O157:H7 in LB medium. We also studied the synergism antibacterial activity of medium chain fatty acid and long chain fatty acid in ruminal and abomasal fluid.Our data indicated that addition of flaxseed to different diet has different influence on the antibacterial activity of bovine ruminal and abomasal fluid. Addition of flaxseed to the grass hay and barley diet increase the bactericidal activity of bovine ruminal and abomasal fluid, however addition of flaxseed to barley silage and barley diet only has influence on antibacterial activity of bovine abomasal fluid not on ruminal fluid. Addition of flaxseed changed the fatty acid composition of bovine gastro-intestinal content and increased the concentration of IgA which indicated the increased intestinal immunity of cattle.In our experiment, capric acid, lauric acid and linoleic acid show the strongest antibacterial activity on E. coli O157:H7 when incubated in pH 2.5 LB medium. The order of anti-E.coli O157:H7 activity of C18 fatty acid at pH 2.5 was as follow: linoleic acid > oleic acid > linolenic acid. The bactericidal activity of fatty acid was decreased with the increase of pH. Capric acid and flaxseed show synergism anti-E. coli O157:H7 activity when added to ruminal and abomasal fluid from cattle fed hay and barley. However, Lauric acid and flaxseed only show synergism anti-E. coli O157:H7 activity when added to abomasal fluid from cattle fed same diet. Both capric and lauric acid did not show synergism anti-E. coli O157:H7 activity when added to ruminal and abomasal fluid from cattle fed barley silage and barley. The antibacterial activity of capric and lauric acid was increased when the bovine abomasal fluid pH decreased to 3.5.In general, addition of flaxseed in bovine diet could partially increase the antibacterial activity of bovine ruminal and abomasal fluid, and this activity may be increased if added medium chain fatty acids at the same time. Addition of flaxseed could increase the immunity of bovine intestinal by increase the secretion of IgA. The immunity increasing function and the antibacterial activity of fatty acid was combinated in our study to give a new suggestion to eliminate the infection of cattle by E.coli O157:H7 without antibiotic resistance.