Forb-rich silage feeding increases milk n-3 and n-6 fatty acid content in practical dairy farming: results from three Danish organic farms

Milk production and milk fatty acid (FA) composition were followed in three Danish commercial organic dairy farms where grass clover silage was substituted with a forb-rich silage. Farms A, B, and C included a total of 50, 189, and 235 lactating dairy cows, and 20 cows in each herd were selected to record the productive performance and milk composition. In all farms, 70% of diets were grass clover silage, and during the experiment, forb-rich silage gradually replaced grass clover silage during the 2–4 weeks, where after cows were fed the forb-rich silage diets for additional 2 weeks. The data were separately analyzed in each farm. Milk production at farms A and B was not affected by diet change, but milk production at farm C decreased by 1.7 kg energy corrected milk (ECM)/cow in cows fed the forb-rich silage. Regardless of farm, the proportion of C18:3n-3, C18:2n-6, and conjugated linoleic acid (CLA) isomers in milk from cows receiving the forb-rich silage increased compared to cows fed grass clover silage based diets. The results indicate the possibility for further increase in the content of poly-unsaturated fatty acids (PUFA) in organic milk by substituting grass clover silage with forb-rich silage.