ABSTRACT
Newly ingested fragments have intrinsic buoyancy due to the structure of large fragments of ingestive mastication. Intrinsic buoyancy of vascular tissues within the relatively large fragments of ingestive mastication is the initial force that positions younger fragments of ingestive mastication into flow paths involving ruminative mastication. With microbial colonization and residence time in the lag-rumination pool, aging fragments undergo age-dependent changes in their masticated size, rate of exposure of new surfaces of microbially accessible PDF (maPDF), and fermentation-based buoyancy. Collective changes of ruminative mastication, fermentation-based buoyancy, and mass action competition among fragments of similar buoyancy constrain ruminal escape of individual fragments until fragments’ surface level maPDF is extensively digested (mean of 90 ± 5%) (Fig. 1A) and fragments are physically masticated to relatively small fragments. We propose[7,8] that the fractional rate of digestion of maPDF provides the fermentation-based buoyancy gradients that constrain the fractional rate of escape of IDF from the rumen (Fig. 1B).
