ffect of concentrate supplementation level on production , health and efficiency in an organic dairy herd

The proportions of organic feed and roughage in the feed ration for organic dairy cows have to reach 100 and 60%, respectively, in 2005. The aim of this study was to elucidate the long-term effects of reducing or omitting concentrate supplementation to high genetic merit dairy cows on a basal ad libitum diet of clover-grass (silage and grazing). Three concentrate levels, N, L and L1 (38, 0 and 19% of dry matter (DM) intake, respectively) were investigated in a herd of 60 cows during 3 years. The production in group N was 6723 kg energy corrected milk (ECM) per cow year, based on an intake of 6226 kg DM of which 38% was concentrates. In group L the omission of concentrates reduced intake to 4770 kg DM, and milk production to 5090 kg ECM per cow year. Milk protein content was reduced and milk free fatty acid content was increased, and the first calving interval was significantly increased, as compared to group N. The intake in group L1 was 5226 kg DM per cow year of which 19% was concentrates. Milk production in group L1 was reduced by only 493 kg ECM per cow year as compared to group N, primarily due to a significantly improved feed conversion ratio (12%). There were no indications of health problems associated with the reduced feeding levels.  2002 Elsevier Science B.V. All rights reserved.