Grass silage in the ration of growing pigs may increase the use of locally produced feed materials. We used a completely mixed ration to avoid selection of compound feed. The realised silage intake in the grower period may be too low in relation to costs of labour and equipment for feeding grass silage. In late finisher pigs a higher proportion of grass silage can be included in the ration since leftovers were small and the realised portion of ingested grass silage was close to 20%. Further increase in the proportion of grass silage may be possible provided that the feeding system allows adequate time and space for feed consumption. Our feeding system with dry feeders limited the silage intake; the optimal feeding system requires further attention. In addition, daily gain, energy utilisation for gain and dressing percentage were lower in silage fed pigs. Thus, the nutritive value of grass silage for growing pigs requires further investigation to clarify and minimise the loss in animal performance. A reduction of the particle size by chopping the grass may improve digestion and reduce spillage of the feed material.