Agroscope Liebefeld-Posieux Research Station ALP, rte de la Tioleyre 4, 1725 Posieux

Fat and fatty acids in preserved forages

This article shows the difference in fat and fatty acid levels between preserved forages and grass. Grass was harvested from the same plot of land at two different stages (30 days apart) over three years and stored using six different processes. 42 samples were analysed by extraction using petroleum ether for fat and by gas chromatography for fatty acids. There was considerable variation in the fat levels (11 to 40 g/kg dry matter (DM)): fodder cut early showing the highest levels (26 versus 20 g/kg DM p < 0,01), and regrowth higher levels than the first cycle (26 versus 21 g/kg MS p = 0,03). Fodder stored as silage had the highest fat level (42 % more than grass content) and fodder dried on the ground the lowest (30 % less than grass content). Linolenic acid was the most important fatty acid with > 55 %. Fatty acid proportions are influenced by the stage of maturity and dry conservation methods reduce linolenic acid proportion. Grass harvested quickly as well as careful handling of the fodder maintain the fat and fatty acid levels.

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