Polyunsaturated fatty acids status in blood, heart, liver, intestine, retina and brain of newborn piglets fed either sow milk or a milk replacer diet.

Docosahexaenoic (DHA) and arachidonic acids (20:4n-6) are deposited in large amounts in the developing neural tissues of the fetus and neonate. The suckling infants receive both fatty acids via the maternal milk, whereas formula-fed infants must synthesize them de novo from their respective precursors, linoleic (18:2n-6) and alpha-linolenic (18:3n-3) acids. We compared the lipid status of 14- and 21-day-old piglets fed either natural milk or infant formula, with special emphasis on the resulting DHA and 20:4n-6 levels in the neural tissues. The two diets presented similar ratios of precursors (18:2n-6/18:3n-3 = 14-16). The sow milk contained 20:4n-6 (0.6% of total fatty acids) and very low levels of DHA (< 0.1%). Formula feeding resulted in higher deposition of DHA in the brain than sow milk feeding, whereas the brain content of 20:4n-6 was not altered. The brain DHA level was negatively correlated with the 18:2n-6/18:3n-3 ratio in the red blood cells (RBC). In contrast, it was not correlated with the DHA concentration in the circulating lipids. The results indicate that the very low amount of DHA in sow milk has no effect on the accumulation of DHA in the piglet's brain, and that natural milk and formula are not equivalent with respect to precursor bio-availability and processing. This difference could be the result of a higher absorption rate and/or the metabolic sparing of formula 18:3n-3. The data support the view that the balance between the essential precursors in the circulating lipids is of vital importance for optimal deposition of DHA in the developing neural tissues.