What cow do we need for grassland based milk production in Switzerland?

The annual milk yield per cow is not a suitable indicator for the efficiency of dairy production because it is strongly influenced by live weight, duration of lactation and production system. The feed conversion ratio (kg energy corrected milk kg dry matter – kg ECM kg-1 DM) or the surface productivity (kg ECM ha-1) are better suited to judge productivity. The milk yield per cow should be expressed per unit live weight (LW; kg ECM 100 kg-1 LW) because the maintenance requirement makes up around 40 % of the annual energy requirement. A dairy herd consisting of large and heavy cows requires relatively more feed surface than a herd of smaller cows. The comparison of large and small Swiss Brown and Simmental/Red Holstein cows in a three year project showed a 6 % higher productivity for the herd of small animals. For the future orientation of dairy breeding the finding that there is a clear interaction between genotype and production system is also important.