The CNCPS v7 has been developed and uses multiple pools of aNDFom to describe digestion and passage. Forages have been analyzed that allow for this approach and when fully implemented, the effect of rumen digestion and rate of rumen emptying can be estimated, thus rumen fill becomes a quantifiable factor. This paper will describe an approach using a large corn silage dataset to evaluate the corn silage hybrids based on what is first limiting rumen fill, total aNDFom intake or uNDF.