Fatty acid composition and regiodistribution in mare's milk triacylglycerols at different lactation stages

The composition and regiodistribution of fatty acids influence the physical and the nutritional properties of milk fat. The aim of this study was to determine the fatty acid composition and the triacylglycerols’ (TAGs) structure of mare’s milk collected on days 20, 40, and 150 postpartum. Differences in the composition of fatty acids occurred between lactation times. A higher proportion of saturated fatty acids, mainly capric (C10:0) and lauric (C12:0) acids, were detected on day 20 in lactation milk TAGs and long-chain unsaturated fatty acids detected on days 40 and 150 lactation milk TAGs. Mare’s milk had interesting nutritional properties due to a high content in essential fatty acids (23.72%). Despite variations in the regiodistribution between lactation periods, fatty acids were generally distributed within the TAGs’ molecules of mare’s milk in a highly specific fashion: from 71.84% to 79.50% saturated fatty acids were mainly esterified in the sn-2 position while unsaturated fatty acids were always preferentially esterified in the sn-1 and sn-3 positions. These results suggest some degree of non-randomness in TAG’s biosynthesis. The fatty acid composition, in particular the level of unsaturation and chain length appeared to be important selectivity factors in the distribution of fatty acids in TAGs’ molecules.