The incorporation of linoleic acid into the plasma lipids of sheep given intraruminal infusions of maize oil or free linoleic acid.

I. The fatty acid compositions of the plasma cholesteryl esters, phospholipids, triglycerides and unesterilied fatty acids were determined in two sheep at various times after they had been given intraruminal infusions of emulsions of maize oil or linoleic acid. 2. The concentration of linoleic acid in the plasma triglycerides began to increase 3 h after infusion began. The infusions of maize oil and linoleic acid resulted in the appearance of peak concentrations of linoleic acid in the plasma triglycerides 6 and 12 h respectively after infusion began. 3. After the infusion of maize oil the plasma triglycerides showed an increasein theconcentration of stearic acid but after the infusion of linoleic acid the plasma triglycerides showed an increase in the concentration of oleic acid. 4. The concentration of linoleic acid in the plasma phospholipids and cholesteryl esters did not begin to increase until 6-9 h and 24-25 h respectively after the infusions had begun. 5. No evidence was found for an absorption mechanism which involved the direct incorporation of linoleic acid into the blood phospholipids or cholesteryl esters.