Intensively fed ruminants receive highly fermentable diets to maximise production of meat or milk. However, highly fermentable diets increase the risk of acidosis, which can result in serious health and productive consequences. Accurate evaluation of feed fermentability in both rate and extent is therefore important in controlling acidosis. Differences in (rate of) fermentation between original raw materials are fairly well established and used in current feed evaluation systems (Van Laar et al., 2004). However, the effects of technological treatments, like grinding and especially pelleting of a feed on fermentability are less well explored. In this experiment the nylon bag method was used to analyse fermentability characteristics of a feed that was ground and pelleted in different ways. Additionally the effect on fermentability of pre-soaking the pellets prior to nylon bag incubation was investigated.