Docosahexaenoic acid in developing brain and retina of piglets fed high or low α-linolenate formula with and without fish oil

Docosahexaenoic acid (22∶6n−3) can be synthesized in the liver and/or brain from α-linolenic acid (18∶3n−3) and is required in large amounts in structural membranes of developing brain and retina. The adequacy and efficacy of formulas containing 18∶3n−3 and/or fish oil in providing 22∶6n−3 for deposition was investigated in piglets fed formula from birth to 15 days. The test formulas contained high (HL) or low (LL) 18∶3n−3 (3.9 or 0.7% of the total formula fatty acids, respectively), or low 18∶3n−3 plus fish oil (LL+FO) to provide C₂₀ and C₂₂ n−3 polyunsaturated fatty acids (0.8% of total fatty acids). Fatty acid analyses of synaptic plasma membrane and retina ethanolamine phospholipids (EPL), which are especially enriched in 22∶6n−3, were compared to those of 15-day-old piglets fed sow milk (SM). Feeding LL resulted in lower 22∶6n−3 in synaptic plasma membrane. Fatty acid levels in HL and LL+FO piglets were equivalent to SM, with the exception of lower 22∶5n−3 in the synaptic plasma membrane of LL+FO and in the retina of HL and LL+FO-fed piglets. Levels of 22∶4n−6 were also lower in the retina of the LL+FO group. The results suggest formula 18∶3n−3 is at least 24% as effective as C₂₀ and C₂₂ n−3 fatty acids as a source of membrane 22∶6n−3. This study shows dietary 18∶3n−3, as the only n−3 fatty acid, can support deposition of comparable percentage of 22∶6n−3 to natural milk. Fish oil also supported tissue levels of 22∶6n−3 similar to natural milk; however, lower 22∶4n−6 may indicate possible inhibitory effects on n−6 metabolism. Recipient of the 1967 Science and Engineering Scholarship, Natural Sciences & Engineering Research Council of Canada.