Que peut-on attendre des pratiques d’élevage pour améliorer la qualité nutritionnelle des matières grasses du lait bovin et caprin ?

This review gives an update of available data on the effect of nutrition on milk fatty acid (FA)composition in dairy cow and goat. It starts by an overview of the main digestive and metabolic pathwaysinvolved in the milk fat secretion processes. Used data are originated from literature and from twodatabases developed by Inra. Altogether, analyses confirm the wide plasticity of milk FA profiles in dairyruminant, peculiarly for the saturated FA (10 to 18 carbon), oleic (9c-18:1) and vaccenic (11t-18:1)acids, and other trans isomers of 18:1 and 18:2. Compared to diets with large amount of concentrateand/or maize silage, grass-based diets (grazed or correctly preserved) show 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 supplementsof plant oil or oilseeds have similar effects than grass feeding, sometimes more marked, but theyincrease simultaneously other trans isomers of 18:1 and 18:2, especially when added to maize silageand/or high-concentrate diets. Oils or seeds rich in 18:2 n-6 (sunflower, soybean,…) increase particularly10t-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. When comparing goats’ withcows’ results, it appears that they are less sensitive to the 11t- to 10t- ruminal shift, thus explainingthe good stability and the large magnitude of the responses of their milk 11t-18:1 and 9c11t-CLAcontent to lipid supplementation of high-concentrate diets. Furthermore, goats seem to respond betterthan cows to 18:3 n-3 rich supplements. Ongoing studies are evaluating the use of milk FA profile asbiomarkers for the authentication of milk according to production zone and type of feeding, or to predictmethane enteric emissions by dairy cows receiving oilseeds. Future studies should also integratethe expected progress of knowledge on the potential effects on consumers of the different major andminor FA found in standard or modified dairy products, as well as putative secondary effects of feedingconditions on sensory quality of dairy products and ruminant health.