Digestibility, intake and selectivity of three mixed-forage pastures by cattle

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Virginia Polytechnic Institute and State University


A grazing trial was conducted to determine the relative value of three mixed-forage pastures, alfalfa-orchardgrass, bluegrass-white clover, and fescue-red clover. Three steers, three heifers and one esophageally cannulated steer were randomly assigned to each pasture treatment. Chemical composition, digestibility, voluntary intake, and selectivity of the forages were determined through use of esophageally cannulated steers and a rare earth marker (ytterbium). Forage intake appears to be most closely related to DM digestibility and content of the NDF and ADF fiber fractions. Some degree of forage selectivity was observed, although the specific species selected for and determinants of selectivity were not apparent. From the data obtained on levels of intake, digestibility and chemical composition, alfalfa-orchardgrass and bluegrass-white clover offer the highest quality forage of the three compared during the time of year studied. Fescue-red clover was consistently inferior in all respects. The digestible dry matter intake by cattle grazing alfalfa-orchardgrass, bluegrass-white clover and fescue-red clover was 3.2, 2.9 and 2.2 kg/d, respectively. More work needs to be done on a wider variety of pastures during different times of the grazing season.