Nitrogen losses following application of pig slurry to grassland represent not only a loss of available N for plant growth, but also a source of air and water pollution by ammonia volatilization, denitrification and nitrate leaching. Previous small scale experiments showed that by reducing the crude protein content of the pigs diet, the slurry nitrogen content was also reduced (Hobbs et al., in press). The aim of this study was to investigate the nitrogen uptake by herbage and losses to the environment following application to grassland of slurry from pigs fed a reduced crude protein diet.