Composition and variability of the branched-chain fatty acid fraction in the milk of goats and cows.

Branched-chain fatty acids of the milk fat of goats were analyzed by high resolution gas chromatography-mass spectrometry. Iso-and anteiso-acids predominated, but a range of other monomethyl-branched components, mostly with methyl-substitution on carbons 4 and 6, was present. Analysis of the milk fat of cows revealed the presence of iso-and anteiso-fatty acid; other monomethyl-substituted fatty acids, as found in the milk fat of the goat, were virtually absent. Only a trace amount of 6-methylhexadecanoate was detected. The difference between goats and cows in the effectiveness with which these animals metabolize propionyl-CoA and methylmalonyl-CoA is discussed.