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Publication Date

1981

Description

Studies were conducted from 1969 through 1974 on northeastern Colorado shortgrass prairie during different grazing seasons and under different grazing intensities to evaluate bison, cattle, sheep, and pronghorn antelope diets. The purpose was to ex­amine seasonal changes in chemical and botanical composition and digestibility of diets of large herbivores. Bison, cattle, and sheep diets were obtained from esophageal fistula samples. Fistula samples were analyzed microscopically to determine botanical composition. Pronghorn antelope diets were obtained by bite-count methodology. Data, presented for im­portant plant species and species groups, were averaged for 28-day intervals to show typical seasonal trends in diets. During all seasons, warm-season grass components were higher in bison diets than in cattle, sheep, and pronghorn diets. Shrubs contributed a greater portion of sheep diets than of bison diets in all seasons and of cattle and pronghorn diets except in autumn. Generally, sheep diets resembled cattle diets more closely than they did antelope diets. The greatest dietary difference was usually between pronghorn and bison. Animals tended to select diets having high crude-protein content. Averaged across all species, dry-matter digestibility of diets did not vary greatly during the year but were somewhat higher in late spring and early summer. As rangelands are grazed more intensively in the future, there will be more emphasis on using several herbivores to maximize vegetation use. Present data are useful in providing information to make decisions for optimally allocating forage to different herbivore species.

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Seasonal Changes in Botanical and Chemical Composition and Digestibility of Diets of Large Herbivores on Shortgrass Prairie

Studies were conducted from 1969 through 1974 on northeastern Colorado shortgrass prairie during different grazing seasons and under different grazing intensities to evaluate bison, cattle, sheep, and pronghorn antelope diets. The purpose was to ex­amine seasonal changes in chemical and botanical composition and digestibility of diets of large herbivores. Bison, cattle, and sheep diets were obtained from esophageal fistula samples. Fistula samples were analyzed microscopically to determine botanical composition. Pronghorn antelope diets were obtained by bite-count methodology. Data, presented for im­portant plant species and species groups, were averaged for 28-day intervals to show typical seasonal trends in diets. During all seasons, warm-season grass components were higher in bison diets than in cattle, sheep, and pronghorn diets. Shrubs contributed a greater portion of sheep diets than of bison diets in all seasons and of cattle and pronghorn diets except in autumn. Generally, sheep diets resembled cattle diets more closely than they did antelope diets. The greatest dietary difference was usually between pronghorn and bison. Animals tended to select diets having high crude-protein content. Averaged across all species, dry-matter digestibility of diets did not vary greatly during the year but were somewhat higher in late spring and early summer. As rangelands are grazed more intensively in the future, there will be more emphasis on using several herbivores to maximize vegetation use. Present data are useful in providing information to make decisions for optimally allocating forage to different herbivore species.