Simulating Grass Seed Passage through the Digestive System of Cattle: A Laboratory Technique

Abstract

Seed of numerous grass species are known to be ingested by cattle (Bos spp.) and remain germinable, while seed of other grass species do not. The seed and animal factors that control the fate of grass seed have eluded researchers. Earlier research showed that seed germination declines linearly with increased residence time in the gastrointestinal tract of cattle. The objectives of this research were to develop modifications to the two‐stage in vitro dry matter digestion procedure (used for evaluating forage digestibility) so the procedure will produce the linear decline in seed germination observed in vivo. A series of in vitro trials was conducted with seed of ‘Alamo’ and ‘Sunburst’ switchgrass (Panicum virgatum L.), TEM‐LD1 kleingrass (P. coloratum L.), ‘Pensacola’ bahiagrass (Paspalum notatum Flugge), and sideoats grama [Bouteloua curtipendula (Michx.) Torr.], with all but the latter having known good seed survival in vivo. The main modification to the two‐stage in vitro dry matter digestion procedure was to shorten the acid‐pepsin phase to about 7 h. We used 24, 48, and 72 h total digestion times to develop the procedure, but screening of species could be done at a single digestion time. Results confirmed that forage similar to diets consumed with seed must be included in in vitro tubes with seed, the acid‐pepsin digestion phase needs to be 7 to 10 h long to provide linear germination responses, and the in vitro procedure will rank species similar to in vivo for relative seed germination. A standardized procedure is described in the text.