The project aims at finding relationships in the chain from grass sward characteristics to milk and manure production. Relationships will be analysed between grass characteristics, grass cultivar x management interactions, productivity and quality, grazing behaviour, grass intake and milk production under zero grazing (stall-feeding) as well as grazing conditions. Cultivars contrasting in morphological appearance, in (rate of) cell wall digestion and in concentrations of water soluble carbohydrates (wsc) will be used to test the hypothesis that these are the major factors determining intake and N use efficiency. In this approach the project aims to study and quantify the effects of grass quality on grazing behaviour and its relation with grass intake, rumen fill, rumen fermentation and rumen clearance, the distribution of N excretion between faecal N output, milk N output and urinary N output. The second, more applied objective is to develop calibration equations for Near Infrared Reflectance Spectroscopy (NIRS) in order to be able to rapidly predict grass growth, intake, nutrient utilization and milk production from NIRS spectra.