Effects of Linseed Lipid on Ruminal Fatty Acid Metabolism, Nutrient Digestibility, Milk Fatty Acid Composition, and Methane Emission in Ruminants

Linseed lipid in the dietary composition is a major factor influencing the fatty acid composition of milk from ruminants, because fatty acids which reach the duodenum are, at least in part, of dietary origin as well as the result of ruminal microbial biohydrogenation of dietary lipids. In this review, the effect of linseed lipid on ruminal fatty acid metabolism, nutrient digestibility, microbial protein synthesis, milk fatty acid composition, and methane emission are discussed. The studies that are undertaken on ruminants mainly use diets supplemented with different linseed forms like linseed oil, extruded linseeds, and rolled linseeds, as sources of n-3 fatty acids. The use of linseed lipid generally increased the flow of cis 18:1, trans 18:1, CLA, 18:3n-3, and total unsaturated fatty acids at the duodenum. Ruminants fed diets supplemented with linseed lipid had greater milk n-3 fatty acids and a sum of unsaturated fatty acids, and lower ruminal methane production. However, a linseed lipid supplement may have some negative effects on nutrient digestibility, microbial protein synthesis, and milk yield. The conclusion is that linseed lipid has a high potential to increase milk fatty acid quality and mitigate methane emission in ruminant feeding.