A feeding trail was carried out in the Organic Dairy Farm of “Haus Riswick“, Kleve, Germany between 1st August 2002 and 31st October 2003 in order to a) investigate the frequently asked question after the “optimal” concentrate-level in Organic Farming and b) relate the concentrate amount to potential health problems of herds associated to the change into Organic Farming. The herd was split into 2 groups of 18 cows. A high quality forage ration was fed to both groups which allowed maintenance plus 19 kg of ECM production on average, which was composed of grass and maize silage in winter, and additional pasture in summer time. The Control-Group (C) received concentrates according to their milk yield, but was not given more than 8 kg/d. The Experimental-Group (E) was fed 3 kg extra concentrates mixed with the forage ration, but did not receive more than 11 kg/d of concentrates in total. Therefore differences between the groups occurred in the first weeks of lactation and in the end of lactation. In 305-day-lactation the C-Group consumed 1600 kg concentrates and the E-Group consumed 2200 kg per cow per year. The results showed a large difference between the seasons. During summer, when cows had access to pasture (half-day), the milk yield was not different between the groups, although the E-Group consumed on average 1,5 kg DM concentrates more than the C-Group. In winter the E-Group produced about 4 kg ECM more than the C-Group. During winter the E-Group consumed 2 kg DM/d concentrates more, which was utilized for milk production. Protein-content in milk showed no differences, fat-content was slightly higher for the C-Group throughout the trial. The results also showed that especially in the first 100 days of lactation the differences between the groups were the largest. The BCS was sufficient during the first 200 days of lactation, even though it was below the optimal score. After 200 days the BCS dropped under the sufficient level, but when cows calved again the BCS was on a sufficient status again. That means that in the last weeks of lactation and in the dry-off period the cows again gained condition
