文献类型： 外文期刊

作者： Jin, L. ¹ ; Wang, Y. ¹ ; Iwaasa, A. D. ³ ; Li, Y. ⁴ ; Xu, Z. ¹ ; Schellenberg, M. P. ³ ; Liu, X. L. ¹ ; McAllister, T. A. ¹ ;

作者机构： 1.Agr & Agri Food Canada, Lethbridge Res Ctr, Lethbridge, AB T1J 4B1, Canada

2.Northeast Agr Univ, Dept Anim Sci, Harbin 150030, Peoples R China

3.Agr & Agri Food Canada, Semiarid Prairie Agr Res Ctr, Swift Current, SK S9H 3X2, Canada

4.Chinese Acad Agr Sci, Inst Grassland Res, Hohhot 010018, Inner Mongolia, Peoples R China

5.Inner Mongolia Acad Agr & Anim Husb Sci, Hohhot 010031, Inner Mongolia, Peoples R China

6.Lethbridge Agr Ctr, Alberta Agr & Rural Dev, Lethbridge, AB T1J 4V6, Canada

期刊名称：JOURNAL OF FOOD PROTECTION （ 影响因子：2.077； 五年影响因子：2.224 ）

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收录情况： SCI

摘要： A 3-year (2009 to 2011) grazing study was conducted to assess the effects of purple prairie clover (PPC; Dalea purpurea Vent) on fecal shedding of total Escherichia coli in cattle. Three pasture types were used in the experiment: bromegrass (Check), mixed cool season grasses with PPC (Simple), and mixed cool and warm grasses with PPC (Complex). Pastures were rotationally grazed during a summer and fall grazing period. PPC was grazed in summer at the vegetative or early flower stage and at the flower or early seed stage during the fall. Fecal samples were collected for enumeration of E. coil and chemical analyses. Forage samples were collected throughout grazing for analysis. Condensed tannins (CT) were only detected in Simple and Complex pastures that contained PPC, with higher concentrations found in the fall than in the summer. Fecal counts of E. coli in cattle grazing Simple and Complex pastures linearly decreased (P < 0.05) over summer to fall in all 3 years, an outcome not observed in cattle grazing the Check pasture. Across the three grazing seasons, fecal E. coli was lower (P < 0.05) in cattle grazing Simple and Complex pastures than in those grazing the Check pasture during the fall. During the fall, feces collected from cattle grazing the Check pasture had higher (P < 0.05) values for pH, N, NH3-N, total volatile fatty acids, and branched-chain volatile fatty acids, but a lower (P < 0.05) acetate:propionate ratio than feces collected from cattle grazing Simple or Complex pastures. In a second experiment, two strains of E. coli were cultured in M9 medium containing 25 to 200 mu g/ml of PPC CT. Growth of E. coil was linearly (P < 0.01) reduced by increasing levels of PPC CT. Scanning electron micrographs showed electron-dense filamentous material associated with the outer membrane of E. coil cells exposed to CT. Incorporation of PPC into forage reduced the fecal shedding of E. coil from grazing cattle, likely due to the anti E. coil properties of PPC CT.