Oxidation and metabolism of linoleic acid in fed and fasted sheep

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Abstract
Summary: Using continuous infusion techniques the entry rate of linoleic acid and its contribution to carbon dioxide production has been studied in fed and fasted sheep. The entry rate of linoleic acid in fasted sheep (0·052 mg/min/kg) was considerably less than that of stearic acid (0·432 mg/min/kg), and the percentage of total carbon dioxide production derived from the oxidation of linoleic acid (0·4%) was also markedly less than that from stearic acid (10·13%).On starvation there was a preferential mobilization of palmitic, stearic and oleic acids relative to linoleic acid.The infused14C-labelled linoleic acid was initially incorporated into plasma phospholipids, with maximal radioactivity at about 1 day post-infusion, and subsequently into plasma cholesteryl esters with a maximum at 2 days post-infusion. The incorporation of14C-labelled stearic acid into plasma phospholipids was only 25–30% that of linoleic acid, with negligible incorporation into cholesteryl esters.Possible explanations for ruminant animals being able to exist on a very low intake of linoleic acid are discussed. In essence, there is a discrimination against the use of linoleic acid as an energy source, but the mechanisms involved do not appear to be unique to ruminant animals.