The challenge of improving nitrogen use efficiency (NUE) in animal production systems must be tackled all along the nitrogen (N) cascade. The general objective of the project is to contribute improving NUE of grassland-based systems by generating improvements at the levels of

1. the recommendations for site-adapted fertilizer applications and stocking rates,
2. the utilization of symbiotically fixed N,
3. the recycling of slurry N,
4. the production and utilization of grassland-grown proteins.

Objective (1) will be achieved by improving the estimation of grassland yields across Switzerland, using measurements from previous projects. Recommendations for the utilization of symbiotic N fixation by legumes will be drawn from data on the effects of clover abundance on residual N, including extensive international collaborations that will allow determining the effects of the site conditions. An established multi-site experiment assessing the effect on NUE of the rate of slurry application on permanent grasslands will be continued. Finally, field trials will be performed within a three-research-groups collaboration to optimize grassland-based protein production and utilization.