Ruminal metabolism and digestion of long chain fatty acids in ruminants: recent advances in knowledge

Abstract

Nutritional quality of animal products is controlled among others by their Fatty Acid (FA) composition, such as a decrease in saturated FA and an increase in n-3 series (omega-3) FA in milk and meat. In ruminants, dietary FA are extensively metabolized in the rumen, mainly through hydrogenation and isomerisation. Composition of FA reaching the duodenum is thus completely different from that of dietary FA, including the appearance of numerous isomers produced by the action of rumen microbes on FA. These processes have been widely studied, but recent improvement in FA analysis techniques on the one hand, and in the knowledge of the ruminal microbial ecosystem on the other hand, have resulted in a rapid refinement of available information. This paper presents the state of knowledge of the mechanisms of ruminal lipolysis and biohydrogenation, including recent data on 20- and 22-carbon FA, on the extent of biohydrogenation and its control by feeding, on the flow and composition of FA reaching the duodenum, on the protection of lipids against biohydrogenation and on FA intestinal absorption. This information allows a better understanding and prediction of the fate of dietary FA, and thus provides tools for a better control of FA composition in ruminant products.