Grassland management is an important part of farm management on a dairy farm.A web application is being developed for dairy farmers to predict the dry matter productionand fodderquality. In a practical pilot on five dairy farms, the model-based estimate of dry matter yield and crude protein content of grass has been compared with grass height and reflection measurements respectively fresh grass analyzes. Due to instabilitythe web application could not yet be used, the test was carried out after the growing season. The prediction of grass yields and crude protein contents gave a mixed picture, sometimes with a good approximation of reality, but sometimes also with clear deviations. For yield, it mainly concerned an underestimation for the first cut and an overestimate for cuts after grazing.For protein, the content was especially overestimated in relatively young grass. Model improvements and combining growth prediction with measurement data make it possible to improve the reliability of estimates.