Preferential Partitioning of Rumen-Protected n-3 and n-6 Fatty Acids into Functionally Different Adipose Tissues

Lipids are stored at various sites inside the body as adipose tissue (AT). These include subcutaneous, abdominal, and intermuscular locations. The AT substantially differ in their metabolic function. It is, however, unclear whether AT have specific requirements for individual essential n-3 and n-6 fatty acids (FA). If so, control mechanisms would partition FA from the blood. To investigate the hypothesis of a selective FA incorporation, 18 beef heifers were fed diets supplemented with 60 g/kg diet with lipids from either fish oil (FO) or sunflower oil (SO). The lipids had partially been rumen-protected to ruminal biohydrogenation of n-3 and n-6 FA. The AT analyzed for n-3 and n-6 FA by gas chromatography were obtained from pericardial, longissimus thoracis (LT) intermuscular, perirenal, and subcutaneous sites. The greatest proportions of n-3 and n-6 FA were found in the pericardial AT. Despite generally low abundance, n-3 FA proportions increased with FO compared to SO supplementation in all AT, but to a different extent. No such partitioning was found for the n-6 FA when supplementing SO. Concomitantly, the n-6/n-3 FA ratio was reduced with FO in all AT, except in the pericardial AT. The latter has specific metabolic functions and thus appears to be quite resistant to diet-induced changes in FA profile in order to maintain its function. The present findings showed the special role of specific n-3 and n-6 FA in bovine AT.