Incorporation of n−3 fatty acids of fish oil into tissue and serum lipids of ruminants

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Abstract
This study examines the biohydrogenation and utilization of the C20 and C22 polyenoic fatty acids in ruminants. Eicosapentaenoic (20∶5n−3) and docosahexaenoic (22∶6n−3) acids were not biohydrogenated to any significant extent by rumen microorganisms, whereas C18 polyenoic fatty acids were extensively hydrogenated. The feeding of protected fish oil increased the proportion of 20∶5 from 1% to 13–18% and 22∶6 from 2% to 7–9% in serum lipids and there were reductions in the proportion of stearic (18∶0) and linoleic (18∶2) acids. The proportion of 20∶5 in muscle phospholipids (PL) increased from 1.5% to 14.7% and 22∶6 from 1.0% to 4.2%; these acids were not incorporated into muscle or adipose tissue triacylglycerols (TAG). In the total PL of muscle, the incorporated 20∶5 and 22∶6 substituted primarily for oleic (18∶1) and/or linoleic (18∶2) acid, and there was no consistent change in the porportion of arachidonic (20∶4) acid.