摘要：The influence of typical feeds from five mountain regions of Switzerland (altitude of grass-based feed (GBF) during the summer and winter seasons: 1247 ($\pm $ 465) m and 1136 ($\pm $ 310) m, respectively) on the fatty acid (FA) composition of bovine milk fat was studied over one year (from May 2004 to April 2005). Compared with winter, summer milk had a significantly lower concentration of saturated FA (SFA) (–8.6%) and significantly higher contents of monounsaturated FA (MUFA) (+19.9%), polyunsaturated FA (PUFA) (+21.7%), conjugated linoleic acid (CLA) (+70.1%), and trans FA other than CLA (+56.7%). Summer and winter milk from mountains did not significantly differ with respect to the contents of branched, $n$-3 and $n$-6 FA. However, the content of the main $n$-3 FA ($\alpha $-linolenic acid) was significantly higher in summer than in winter milk and its content was positively correlated with increasing percentages of GBF and altitude.
