There is a need to develop cost-effective means of utilising slurries on grassland used for grazing or cut for silage without incurring adverse effects on animal performance. This study will aim to quantify the risks of adverse effects of slurry application to grassland on animal performance and silage quality, and will provide recommendations on means of avoidance. A critical review of existing literature will be undertaken and field experiments will be conducted to assess the effects of cattle slurry application during the growing season on herbage production silage quality. These experiments will include 2 methods of slurry application (surface spread and shallow injection) at different times between approximately 10 weeks and 1 week prior to cutting for silage in early, mid or late season. At harvesting, the cut herbage will be ensiled in mini-silos (approximately 80 l capacity) for about 100 days. Analyses performed on fresh herbage will include fresh weight yield, dry matter content, total N, P and K contents, protein content, digestibility and water soluble carbohydrates. Silage will be analysed for dry matter, ammonia-N, pH, energy value, crude protein and volatile fatty acids. Another series of experiments will be conducted to assess the effects of cattle slurry application on herbage intake by grazing cattle. Grass swards will be established in open boxes and offered with and without slurry to cattle, and feeding responses will be recorded. Results from these experiments will be used in the design of longer term, field grazing experiments to enable the effects on herbage intake and animal performance to be measured. These experiments will examine the interactions between slurry application, herbage availability and intake by grazing cattle and how these might change with time. Results will also be used to formulate improved recommendations for farmers. A brief leaflet will be produced summarising overall results of the study and providing advice to farmers on slurry utilisation.