Arachidonic acid concentrations in plasma and liver phospholipid and cholesterol esters of piglets raised on formulas with different linoleic and linolenic acid contents.

The influence of sow milk or infant formulas containing 18:2n-6 and 18:3n-3 (% fatty acids) at 30/1, 16/1, 35/4, or 16/4 on plasma and liver phospholipid (PL) and cholesterol ester (CE) arachidonic acid (20:4n-6) was studied in piglets fed from birth for 15 d. Piglets fed the 35/4, 16/1, and 16/4 formulas had a significantly lower percentage of plasma 20:4n-6 in PL than did piglets fed sow milk or the 30/1 formula. The lowest plasma PL 20:4n-6 was in the 16/4 group, the only group in which liver PL 20:4n-6 was significantly reduced. This suggests competitive inhibition of synthesis or acylation of 20:4n-6 when formula with a high content of 18:3n-3 is fed in conjunction with a low content of 18:2n-6. The percentage of plasma CE 20:4n-6 was not altered by formula feeding. In contrast, the liver CE 20:4n-6 was significantly lower in all formula-fed animals than it was in sow-milk-fed animals. These studies confirm that 20:4n-6 metabolism is altered in artificially fed neonates. Liver and plasma cholesterol concentrations were also significantly lower in all formula-fed than in milk-fed piglets. The potential relationship of the decrease in cholesterol to n-6 fatty acids in CE is unknown.