Effect of dietary fatty acid composition on fatty acid profiles of polar and neutral lipid tissue fractions in zebra finches, Taeniopygia guttata.

The growing awareness that the fatty acid (FA) composition of the diets of birds, and ultimately their tissues, influence physiological performance variables, such as aerobic capacity, thermosensitivity, digestive efficiency, etc., underscores the need to understand how differences in dietary fatty acid composition actually translate into differences in the fatty acid composition of specific tissues. We quantified the fatty acid profiles of polar and neutral lipid fractions of several tissues in zebra finches (Taeniopygia guttata) and compared these profiles among birds fed either a control diet of only hulled millet, or one of two experimental diets of hulled millet supplemented with either 8% (by mass) sunflower seed oil (omega6-enriched diet) or linseed oil (omega3-enriched diet). We found that different lipid fractions vary widely in their diversity and complexity of FA composition, with neutral lipids being much less structurally diverse than those of polar lipids, for example, and that the fatty acid compositions of different organs exhibited different propensities to be altered by the diet, with brain and cardiac tissues having lower levels of flexibility than skeletal muscle and liver. We also present evidence suggesting that adipose tissue may be used to sequester essential FAs when they occur in the diet at levels that exceed immediate requirements. We conclude that the fatty acid composition of adipose tissue may not be a particularly useful indicator of the dietary FA composition of birds, and suggest that future studies investigating the relationships between the FA profiles of bird tissues and bird diets and/or physiological performance variables examine multiple tissues and distinguish between neutral and polar lipid fractions.