Fatty acid composition and fat content in milk from cows grazing in the Alpine region

The variation in the fat profile of pooled milk from cows grazing in pastures in June and July at 400-700 m and at 1400-2250 m of altitude was evaluated by gas chromatography and compared with that from cows stalled in barns and fed with a diet without fresh grass. The ratios unsaturated/saturated fatty acid in milk samples were 1.33, 1.71 and 1.69 in June and 1.21, 1.69 and 1.84 in July for cows fed with prepared diet, grazing at 400-700 m or grazing at 1400-2250 m, respectively. Analogously, the ratios (oleic plus stearic acid)/palmitic acid were, for the same group of cows, 0.59, 0.72 and 0.78 in June and 0.56, 0.73 and 0.81 in July. In milk from pastured cows, the percentage of oleic, vaccenic, rumenic and ?-linolenic acids increased as a function of the altitude; instead, that of linoleic acid and of cis-12-octadecenoic acid decreased. The yield of fat was always highest in milk from 1400 to 2250 m of altitude (up to 3.6 g per 100 mL). For the milk collected in July at 1400-2250 m of altitude, it was observed a decrease in the percentage of decanoic (capric) and dodecanoic acids and an increase in pentadecanoic, stearic, arachidic and docosanoic (behenic) acids. Possible reasons for the differences observed in the milk samples were discussed.