The effects of feeding various forages on fatty acid composition of bovine milk fat: A review

The nutritional image of bovine milk fat has suffered for years because of the association of saturated fatty acids and coronary heart disease. Thus the alteration of fatty acid composition has been a long-term strategy. Forages, even though containing a relatively low level of lipids, are the cheapest and often the major source of beneficial unsaturated fatty acids in ruminant diets. Recent progress in the research of factors affecting fatty acid content and composition in fresh and preserved forages and the associations between feeding such forages and milk fat profile are reviewed. Milk from cows grazed or fed fresh forage, especially from species-rich grasslands or forage legumes, has a considerably higher ratio of unsaturated to saturated fatty acids and a higher content of nutritionally beneficial trans-fatty acids (e.g. CLA, vaccenic acid) than milk from cows fed silage or hay. Grass and legume silages seem to affect the fatty acid profile more propitiously than maize silage.