The pepsin soluble dry matter of leaf and stem fractions of grasses in relation to voluntary intake by sheep

Abstract

The level of pepsin soluble dry matter (PSDM) was determined on leaf and stem fractions derived from five grasses each cut at three stages of growth. The voluntary intake and dry matter digestibility of all grass fractions had been previously determined with sheep. Mean PSDM for leaf and stem were similar (23.0 v. 23.4 per cent) despite large differences in voluntary intake (57.8 v. 39.6 g/kg W0.75 )and similar dry matter digestibility (52.6 v. 55.8 per cent). For all grass fractions the correlation between voluntary intake and PSDM was r = 0.26, P > 0.05. This poor relation was partly caused by a significant difference between the leaf and stem populations. It was concluded that PSDM was an unreliable guide for predicting the voluntary intake of grasses when compared at similar stages of growth.