1. Groups of turkeys were given, to 10 weeks of age: diets E, basal, containing 2.3% mainly cereal lipid; A, basal plus 2.5% beef fat; B, basal plus 2.5% anchovy oil; C, as B, plus 0.02% ethoxyquin; D, basal plus 5% anchovy oil. Lipids from breast and leg muscle of all five groups were fractionated by thin-layer chromatography into five ‘neutral’ and six phospholipid fractions and the fatty-acid composition of each was determined by gas–liquid chromatography.
2. Individual lipid fractions differed widely in fatty-acid composition and in the degree to which they could be influenced by dietary fat supplements. Small but usually consistent differences were observed between corresponding fractions from breast and leg. Sphingomyelin (SP) and lysophosphatidylcholine contained largely saturated acids (76–80%); the other phospholipids were 44–48% and the ‘neutral’ lipids 38–50% saturated. Phosphatidylserine (PS), phosphatidylinositol(PI) and, in less degree, phosphatidylethanolamine (PE) were rich in stearic acid, though palmitic was much more abundant in the diets and in the other muscle lipids. SP contained no acid more unsaturatedthan linoleic (1–2%). PE and PI were richest in arachidonic and PE and PI in other polyene acids.
3. The effects of beef fat on the muscle lipids were small and mainly on the ‘neutral’ fractions.
4. The polyunsaturated fatty acids of the fish oil extensively displaced linoleic (and oleic) acids from all fractions (except SP); arachidonic acid was displaced from PE but not from PI.
5. The degree to which the fish-oil polyunsaturated acids of the three series entered the muscle lipids varied with the acid and with the fraction. Docosahexaenoic acid (22:6) reached a concentration of 20–25% in PE, nearly five times as great as its concentration in the dietary lipid.
6. Hydrolysis with phospholipase A showed that most of the unsaturated fatty acids were present in the 2-position of PC and PE, but the positional specificity was not complete, particularly for the less highly unsaturated acids.
7. The antioxidant ethoxyquin had no effect on the fatty-acid composition of any of the muscle lipid fractions.