Voluntary intake and in vivo digestibility of herbage harvested from five indigenous communities–Agrostis-Festuca, Nardus and Molinia grasslands and Eriophorum vaginatum- and Trichophorum caespitosum-dominated varieties of blanket bog–and also from sown Lolium perenne and Trifolium repens swards were measured over two years. First growths of each sward were harvested at three stages of maturity and stored at — 20°C before feeding. Voluntary intake was measured while feeding ad libitum to 15% excess of the intake on the previous day and digestibility when feeding at 80% of voluntary intake.

There was a common positive relationship (r2= 0·86***) between intake (adjusted for year of feeding, range 72·8–16·7 g organic matter (kg LW)0·75 d-1) and organic matter digestibility (range 0·796–0·371), covering Lolium perenne and most of the indigenous communities. However, there were significant differences between the regressions of intake on the concentration of neutral detergent fibre for ryegrass and the indigenous communities, and also between the regressions for individual communities.

The results demonstrated the general value of organic matter digestibility as a predictor of intake potential, and the high digestibility and intake potential of immature vegetation from the grass and grass heath communities.