THE IN VITRO DIGESTIBILITY AND PROTEIN CONTENT OF LEAF AND STEM PORTIONS OF FORAGES

Abstract

The in vitro dry matter digestibility (I.V.D.) of the immature stems of timothy, orchardgrass, and bromegrass was higher than that of the leaves. However the rate of decline of digestibility with advancing maturity was greater with stems. At head emergence the I.V.D. of the leaves of orchardgrass was similar to that of the stems. Wide differences existed, though, in the I.V.D. of leaf and stem fractions of orchardgrass at more advanced stages of growth. Digestibilities of the plant parts of both timothy and bromegrass were not greatly different at any growth stage.The digestibility of leaves of alfalfa decreased only slightly as the season progressed. However, the I.V.D. of the stems declined rapidly early in the season. Unlike the grasses, the stems of alfalfa never attained as high a digestibility as the leaves at the early growth stages.The crude protein content of both leaf and stem portions of the various grass species was similar.As the season progressed, orchardgrass had the highest leaf to stem ratio and bromegrass the lowest. Even within a species, leaf content was a rather poor indicator of digestibility.