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<li> Conduct cattle feeding trials to monitor effects of grain and feed additives on colon pH and numbers of acid resistant E. coli; </li>
<li> determine effect of dietary alterations on long term effects on acid resistance of E. coli; </li>
<li> determine effects of pH, nutrient starvation and fatty acids on acid resistant E. coli. </li></ol>
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Non-lactating cows fitted with ruminal cannulae will be used in 3 X 3 and 4 X 4 Latin square design to determine the effects of different aspects of the diet on numbers of virulent, acid resistant E. coli in cattle. <br>
These will include:
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<li> effect of grain on numbers of acid resistant E. coli;</li>
<li> switching cows from a grain to forage diet to determine time necessary to reduce numbers of acid resistant E. coli; </li>
<li> effect of the feed additive monensin on numbers of acid resistant E. coli;</li>
<li> effect of grain source (rolled corn, rolled barley, steam flaked corn) on rumen pH and numbers of acid resistant E. coli. </li> </ol></p>
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Samples of ruminal fluid will be collected from the rumen via ruminal cannulae and analyzed for pH, fermentation acids, and bacterial counts. The persistance of dietary dependent differences in E. coli acid resistance will be determined by inoculating raw hamburger with either:
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<li> acid resistance or sensitive E. coli cultures, or </li>
<li> fecal matter from cattle fed grain or forage. </li></ol>
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