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Healthy fatty acids in forage

Healthy fatty acids in forage

Forage has a healthier fatty acid composition than cereal based concentrates. Forage contains the unsaturated linoleic and α-linolenic acids (C18:2 and C18:3) and the latter makes up no less than 55-75 per cent of total fatty acid content in plants. In both human and animal studies dietary unsaturated fatty acids have shown to have health benefits. So only by increasing the forage part of the diet one can increase the intake of healthy fatty acids, but it is also possible to influence the crop to increase the unsaturated fatty acid part of the forage.

A Swedish study has shown that neither prewilting nor additives notably affected the fatty acid composition during ensiling of timothy from the first and second harvest. There were some differences between fresh crop and silage which indicates that changes in the fatty acid composition occurs during ensiling. However these differences were so small they do not have any effect in practice.

Nitrogen (N) fertilization can also have a positive effect on both the total amount of fatty acids and the relative amount of unsaturated fatty acids. This study showed that the fatty acid concentration tended to increase in timothy and meadow fescue with higher N fertilization. In addition there were strong linear correlations between the concentration of both individual and total amount of fatty acids and the concentration of crude protein, the higher the crude protein the higher amount of fatty acids. Clover also generally contains both more crude protein and more unsaturated fatty acids than grass.

The highest concentrations of fatty acids were found early in the season when the grasses were still in leaf stage. During the regrowth the grasses maintained in leaf stage during longer time but the fatty acid concentration still decreased, which indicates that light intensity and temperature matters more during regrowth than early season.

Free fatty acids, also called volatile fatty acids, are easily lost after the bale is opened and the silage is exposed to oxygen. With less free fatty acids unsaturated fatty acids are better preserved in the silage also during feeding. So when opening a bale we do not have to worry about losing the healthy unsaturated fatty acids!

Sara Muhonen, AgrD

References:
Arvidsson K 2011. Fettsyror i vall och mjölk. Djurhälso- & Utfodringskonferensen 2011, Svensk Mjölk, sid 1-2. (In Swedish)

Arvidsson K 2009. Factors affecting fatty acid composition in forage and milk. Doctoral thesis. Acta Universitatis Agriculturae Sueciae 2009:62.

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