New guide values for the nutrient excretions of dairy cows

In the framework of the current revision of the Swiss Fertilizer Guidelines (SFG) the guide values for nutrient excretion and forage consumption of dairy cows were checked and adapted to current production practice. The principle used for calculating excretions is input in feed minus retention in milk, calf and growth. A model based on the official Feeding Recommendations was used for the calculations. Concerning the current production practice data from a representative survey performed in 2010 were available, which were much more detailed than what was used in previous calculations. Apart from the milk yield the importance of different forage diets and the distribution of calving over the year could thus be considered in the calculations. The basis scenario is for a milk yield of 7500 kg per cow per year. The excretions are 112 kg N, 16 kg P und 143 kg K and the forage consumption is 5600 kg per cow and year. For lower and higher milk yield a linear correction factor is proposed. In spite of the higher milk yield as compared to the previous edition of the SFG from 2009 the new guide values are lower than the old ones. This can be explained with changes in the production practice, e.g. more hay and maize silage complementation to grass and higher amounts of concentrate used, as well as with the new methodology of calculation and revisions in the Feeding Recommendations.