• Changes in Concentrations of Tannins, Total Phenolics, Crude Protein, and In Vitro Digestibility of Browse due to Mastication and Insalivation by Cattle

      Burritt, E. A.; Malechek, J. C.; Provenza, F. D. (Society for Range Management, 1987-09-01)
      The feasibility of using esophageal extrusa to monitor dietary tannin levels was studied using 4 shrub species (Purshia tridentata, Quercus gambelii, Cercocarpus montanus and Acer grandidentatum). Browse samples were hand-harvested in late summer. Half of the sample for each species was fed to esophageally fistulated cattle, while the other half served as an unmasticated control. Extrusa and control samples were analyzed for total phenolics (Folin-Denis), tannin using 3 methods (vanillin-HCl, proanthocyanidins, and astringency), crude protein, and in vitro organic matter digestibility (IVOMD). Tannin levels were reduced 10% to 60% in extrusa, depending on plant species and method of tannin analysis. Changes in the nutritional constituents of extrusa were limited but oak extrusa was higher in IVOMD than oak control samples. Tannins may have bound to plant or salivary proteins or to mucous membranes in the mouth during mastication and insalivation. Our results indicate that esophageal extrusa is not suitable for monitoring dietary tannin levels.
    • Vegetation Trends within Rest-Rotation and Season-long Grazing Systems in the Missouri River Breaks, Montana

      Watts, C. R.; Eichhorn, L. C.; Mackie, R. J. (Society for Range Management, 1987-09-01)
      Trends in canopy-coverage of vegetation and bare ground were measured inside and outside exclosures on recent burns within three-pasture rest-rotation and season-long grazing systems over a 10-year period. Results suggested that rest-rotation grazing may maintain vegetation and soil cover somewhat comparable to ungrazed cattle exclosures on rough breaks-type range in north-central Montana. Season-long grazing may not maintain satisfactory vegetation and soil cover in the area.