Auteur: Abbink G.W., Reijneveld J.A. and Linders P.B.J.
Jaar van uitgifte: 2015
In the Netherlands, the amounts per ha of nitrogen (N) and phosphorus (P) applied have been reduced by approximately 40% since 1996, due to legislative restrictions. However, as the reductions in N and P fertiliser application have not resulted in a reduction in the dry matter (DM) yield of grassland, we hypothesise that herbage quality is changing. We used a large database (n>350,000) with results of spring forage analyses from dairy farms in the Netherlands. In the period studied (1996-2013), crude protein (CP), crude ash, P, K, Fe, Zn, Mo, Cu and Co content all decreased. In the same period, an increasing content of energy, water-soluble carbohydrate (WSC) and selenium was found. The decreasing CP levels probably induced the increase in the WSC content of herbage. The increase in Se content can be explained by the increased use of Se containing fertilizers. In conclusion, almost all mineral contents in herbage seem to decrease because of the legislative restriction on N and P input. In order to maintain high animal production levels, farmers need to purchase high-protein feed and minerals for their rations to compensate for the decreasing CP and mineral contents in silage.