Recent data on the effects of feeding factors on cow milk fatty acid composition

This review gives an update of available data on the effect of nutrition on cow milk fatty acid (FA) composition. It starts by an overview of the main digestive and metabolic pathways involved in the milk fat secretion processes. Used data are originated from literature and from one database developed by INRA. Altogether, analyses confirm the wide plasticity of milk FA profiles in dairy cow. peculiarly for the saturated FA (10 to 18 carbon), oleic (9c-18:1) and vaccenic (111t-18:1) acids, and other trans isomers of 18:1 and 18:2. Comparing effects of diets with large amount of concentrate and/or maize silage with grass-based diets (grazed or correctly preserved) shows a decrease in saturated FA, at the expense of 9c- and 11t-18:1, and to a lesser extent, 18:3 n-3 and 9c11t-CLA. Dietary supplements of plant oil or oilseeds have similar effects, sometimes more marked, but they increase simultaneously other trans isomers of 18:1 and 18:2, especially when added to maize silage and/or high-concentrate diets. Oils or seeds rich in 18:2 n-6 (sunflower, soybean,...) increase particularly 10t-18:1, and 10t12c-, 8t10c-, 7t9c- and 9t11c-CLA, whereas those rich in 18:3 n-3 (linseed) enhance notably 13t/14t-18:1, and 9ct12-, 9ct13- and 11tc15-18:2.