The Less Favoured Areas (LFAs), which occupy almost half of the agricultural land in the UK, can be divided into two categories: rough grazing (semi-natural) and grassland (improved permanent pasture and temporary grass). Although rough grazing accounts for two-thirds of the land, it contributes only 15% to total output. However, it is this category that requires more sympathetic grazing management if its environmental value is to be maintained or enhanced. While some information exists on the impact of grazing by cattle on semi-natural vegetation communities such as Molinia caerulea (Grant et al., 1996) there is a lack of information on the effects that grazing with cattle or sheep over the summer months might have on animal performance. The underlying hypothesis for this experiment was that grazing in summer would have beneficial effects on animal performance through changes in the short term in the structure of the vegetation, and in the long term through changes in both structure and species composition.