Variation in the fatty acid composition of Alpine grassland during spring and summer.

The main objective of this research was to study the variability of fatty acid (FA) concentration and composition in forage during the primary growth of one of the most typical grasslands in alpine regions. During two years, the grassland was sampled from May, when grazing would typically begin, to July, when haymaking was typically performed due to favorable weather conditions for drying forages. The total FA (TFA) concentrations of herbage, as well as nutritional quality, was negatively related to the plant age and decreased throughout the growing cycle. This negatively affected the forage concentration of ?-linolenic acid (C18:3 n-3), the main precursor of health FA in milk fat, which decreased throughout the growing stages, showing a negatively relationship with the oleic acid (C18:1 n-9) both in grassland samples and in individual forage species. It has also been observed a different concentration of TFA between the two years, and the drought conditions recorded during 2003 could have negatively affected herbage FA concentration and composition. The higher forage concentration of C18:3 n-3, as well as elevated nutritive value, could be obtained by an early utilization of the sward by grazing or harvesting, providing a greater amount of FA precursors in animal diets, with consequent positive effects on milk FA profiles. However, proper management and particular attention must be paid in year characterized by moderate to severe drought stress, which could negatively affect the TFA concentration of forages.