Animal Science, Department of


Date of this Version



Published in Nebraska Beef Cattle Report 1998, published by Agricultural Research Division, University of Nebraska Cooperative Extension, and Institute of Agriculture and Natural Resources, University of Nebraska–Lincoln.


This two-year study was conducted on monocultures of switchgrass and big bluestem to: (1) determine the concentration of the protein ribulose-1,5- bisphosphate carboxylase (Rubisco), found only in the bundle sheath cells of warm-season grasses, in omasal, masticate and fecal samples of grazing cattle; and (2) estimate rumen-escape Rubisco via bundle sheath cells. A quantifying enzyme-linked immunosorbent assay, along with estimates of rumen and lower tract digestibilities, indicated as much as 11% of Rubisco in big bluestem and 13% in switchgrass escaped rumen degradation and was absorbed in the lower tract. Realizing these amounts of escape Rubisco represent a significant level of soluble protein, bundle sheath cells may provide a mechanism allowing soluble protein to escape ruminal degradation.