Linolenic acid provides a source of docosahexaenoic acid for artificially reared rat pups.

The goal of the present study was to determine the effectiveness of linolenic acid for enriching docosahexaenoic acid (DHA) in infant rats. Seven-day-old rat pups were artificially reared and fed intragastrically for 8 d a milk substitute containing either 1) corn oil, high in linoleic acid (35.6 g/100 g fatty acids, 775 kJ/L); 2) menhaden oil, high in DHA (3 g/100 g, 67 kJ/L) and eicosapentaenoic acid (EPA, 6 g/100 g, 132 kJ/L); or 3) linseed oil, rich in linolenic acid (34 g/100 g, 750 kJ/L). Growth rates were comparable among the artificially fed pups and those raised by lactating dams. Feeding the DHA precursor linolenic acid enriched EPA in plasma, erythrocytes and liver, but enriched DHA only in the liver, compared with feeding corn oil. The proportion of liver DHA in the pups fed the linolenic acid-rich substitute was twice that detected in the corn oil-fed pups and 60% of the level found in the pups fed the preformed DHA. The significant elevation of hepatic DHA indicates active desaturation and elongation in the developing rat liver. The failure to enrich erythrocyte DHA suggests the need for caution in the use of erythrocytes as an index of DHA status in tissues capable of in situ synthesis. The artificial rearing of rat pups was proven suitable for studying the interaction of dietary manipulation and tissue accretion of essential fatty acids during the postnatal development.