The pattern in which ruminants consume their daily allocation of forage may affect their total daily intake and the pattern of supply of energy and protein to the micro-organisms in the rumen. Synchronizing energy and nitrogen supply to the rumen has been demonstrated to improve the efficiency of microbial protein synthesis (Sinclair et al. 1993, 1995). However, it remains unclear whether animals, when offered a feed with a predicted asynchronous release of nutrients, will alter their pattern of intake to achieve a synchronous supply. In addition, the provision of a concentrate may alter daily intake, hourly intake and the pattern of release of nutrients in the rumen. The objectives of the current experiment were to examine the effects of level of supplement on the pattern of intake and the predicted release of nutrients in the rumen in sheep fed grass silage.