Fatty acid composition of the plasma lipids of newborn and maternal ruminants.

1. The fatty acid compositions of the plasma lipids of newborn unsuckled lambs, kids, calves and piglets have been determined and compared with those of maternal plasma lipids at parturition. 2. The predominating plasma fatty acids in the newborn of all species are palmitic acid, C(16:1) acid, stearic acid and C(18:1) acid. This finding is consistent with the synthesis of the major proportion of fatty acids from non-lipid sources within the foetus. 3. Very small amounts of C(18:2) acid and C(18:3) acid are present in the plasma lipids of newborn ruminants, although considerable amounts of these fatty acids are contained in maternal plasma. The plasma fatty acids of the newborn piglet contained 5.5% of C(18:2) acid, those of the calf 2.0%, and those of the lamb and kid less than 1.0%. This finding is discussed in relation to the higher content of C(18:2) acid in the plasma non-esterified fatty acid fraction of the sow (15%) compared with that of the ruminant (less than 4%). 4. In the lamb and kid, but not in the calf or piglet, a C(20:3) acid was detected in plasma lipids that was very similar to, if not identical with, the C(20:3) acid that accumulates in the plasma of animals given diets low in essential fatty acids. The possible significance of this finding is discussed. 5. The cholesteryl esters of cow plasma were found to contain a higher percentage (43%) of C(18:3) acid than those of goat and sheep plasma (5-10%). The possible reasons for this difference are discussed.