Seasonal variation in fatty acid composition of cow milk in relation to the feeding system

The fatty acid (FA) composition of bulk milk fat was examined on three dairy farms applying the seasonal pasture and on two farms applying the permanently indoor silage feeding. The seasonal variation in the content of major FAs was investigated in relation to the effect of farm in each feeding system separately. Six samples in winter period and four samples in summer period were taken on each farm. In the grazing herds, the seasonal changes were found in FAs forming 90 g/100 g total FAs on average (P>0.05), generally without interactions with farm effect (P>0.05). Only several FAs, forming 14 g/100 g total FAs on average, were influenced by the season effect in the indoor herds (P