Fatty acid composition of liver lipids of young lambs.

I . The changes in the lipid composition of livers from lambs receiving either ewe’s milk or a reconstituted low-fat milk powder have been studied during the first 8 d after birth. 2. At birth the phospholipid and unesterified fatty acid fractions constituted the major proportion of the liver lipids. In the lambs on the artificial diet the relative concentration of the phospholipid fraction increased and there were corresponding decreases in the relative concentrations of all the other fractions, whereas in the naturally fed lambs the relative concentration of the phospholipids remained similar to that found in the livers at birth. 3. In the liver lipids at birth there were only low concentrations of the CIS polyunsaturated fatty acids, although there were appreciable concentrations of the higher C,, and C,, polyunsaturated fatty acids. 4. After birth there was a large increase in the concentration of the CI8 polyunsaturated fatty acids in the livers of the lambs on the natural diet and a decrease in the 20 : 3 w9 : 20 : 4 w6 (triene : tetraene) ratio. In the lambs receiving the artificial diet the concentration of the CI8 polyunsaturated fatty acids and the triene : tetraene ratio remained similar to that observed at birth. 5 . These changes are discussed in relationship to the metabolism of the essential fatty acids in monogastric animals.