Leguminous crops represent a potentially valuable source of protein and energy for the ruminant. They promote higher levels of microbial activity in the rumen than most other feeds (Agricultural Research Council, ARC, 1984), probably because of their content and rate of release of nutrients. Thus, they may be useful supplements for low quality roughages. Levels above 0.15 - 0.20 long or chopped legume hay included in low quality roughage based diets result in a reduction in the intake of the basal roughage (Lane, 1982; Minson and Milford, 1967; Mosi and Butterworth, 1985; Siebert and Kennedy, 1972). This substitution effect may be due to a rumen physical limitation and/or a limiting nutrient supply for the rumen micro-organisms. The objective of this work was to study the effect of supplementing straw with lucerne pellets on the digestion kinetics and intake of the dietary components.