Milk fatty acids in relation to feeding practices on Dutch organic farms Jande WitauthorJan PaulWagenaarauthorAnnekede VriesauthorTonBaarsauthorVarious recent studies have indicated positive interactions between organic animal production and poly-unsaturated fatty acids, particularly CLA and omega-3. In this paper, we present the monitoring results of 15 organic farms concerning the rela-tionship between feeding practices and fatty acid pattern. The results indicate a strong negative effect of maize and grass silage and concentrate feeding on CLA levels in milk fat. On the other hand, feeding fresh grass has a positive effect. Omega-3 levels in milk fat seem less related to feed characteristics: similar relations to those with CLA seem to exist, but feed composition explains the variation in omega-3 levels only to a limited extent, while there is a large farm influence. This might be related to the energy balance of the cows. A comparison of measured CLA and omega-3 levels in organic milk with common levels in conventional milk shows a small difference during the stable period. Effects of adding oil - as a possibility to improve the level of CLA and omega-3 in a way that is organically acceptable - are explored, but effects remain small. Food security, food quality and human health Dairy cattle2006Conference paper, poster, etc.