Monitoring the effect of grass production strategies within the ‘Koe and Eiwit’ project

In the ‘Koe en Eiwit’ (Cow and Protein) project, 150 Dutch dairy farmers aim to reduce dietary CP level to 155 CP g (kg DM)–1 to lower ammonia losses. Ration CP level is influenced by CP content in grass silage. The aim of this research is to study: (1) what are the goals in CP level that farmers set for grass silages in the beginning of the year? (2) how are these goals translated into fertilization plans, and (3) what was the success rate of obtaining the goal set for CP level of grass silages. Farmers were visited in 2023 and questioned on their goal for CP level in grass silage, intended fertilization, and the realized CP level in grass silage. On average, farmers did not set lower goals for the CP level in grass silages than realized in 2022. Intended fertilization levels seemed consistent with goals for grass silage CP level. Success rate (as a fraction) of reaching the intended CP level category varied from 0.50 to 1 for the 9 groups, consisting of the first 3 cuts of grass silage on 3 soil types (peat, clay and sand). Success rate was not statistically different between groups.