BackgroundOmega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) are of interest because of their health effects. However, most experiments use natural oils and are confounded by PUFA concentrations and other fatty acids (FAs) that impact biosynthesis of the very long-chain derivatives (VLC). ObjectivesTo directly compare the effect of 18 C n-3 or n-6 FA fed at similar rates on their elongation and desaturation to VLC PUFA and their incorporation into tissues. MethodsOil blends that substituted ∼23% points of stearidonic acid (SDA) with alpha-linolenic acid (ALA), gamma-linolenic acid (GLA), or linoleic acid (LA) while minimizing differences in other FA were prepared. COBB500 broilers were fed the oil blends at 1.25% of the diet from day 14–35 age. ResultsThere was greater enrichment of VLC PUFA in breast, thigh, liver, and plasma when diets were supplemented with high-SDA and high-GLA oil blends than high-ALA and high-LA oil blends. The efficiency of VLCn-3 PUFA synthesis from SDA and ALA was lower than the efficiency of VLCn-6 PUFA synthesis from GLA and LA, suggesting that the elongation and desaturation enzymes more efficiently utilized n-6 substrates. The efficiency of biotransformation of SDA to VLCn-3 PUFA was greater than that of high-ALA, and synthesis of VLCn-6 PUFA from GLA was higher than that of high-LA in breast, thigh, liver, and plasma. There were minimal effects on tissue-saturated and monounsaturated FA. ConclusionsThe high-SDA and high-GLA oil blends efficiently enriched tissues with their VLC-PUFA more than high-ALA and high-LA treatments.