New Perspectives on Lipid Digestion and Metabolism in Ruminants

Fat is an important energy component in the diet of ruminants and over the last decade fat supplementation has become a common practice to increase the energy density of the diet for high producing dairy cows. Recent advances have renewed the interest in dietary fats and lipid metabolism. One development is improved analytical procedures which have revealed the complex pattern of fatty acids that are produced in the rumen and incorporated into ruminant meat and milk fat. The old adage “what you eat is what you get” is clearly incorrect in the case of dietary lipids and ruminant animals, and this is of special importance given recent efforts to include lipid metabolism in dynamic models of ruminant digestion. Following absorption, a major fate of fatty acids is their oxidation for energy. However, a second recent development is the recognition that specific fatty acids produced in the rumen also play a critical role as signaling molecules involved in the expression of specific genes and the regulation of metabolic processes. Finally, recent discoveries in the functional foods area indicate that specific fatty acids produced in the rumen may have beneficial effects on human health, and there is a keen interest in the possibility of designing natural food products with enhanced levels of these fatty acids.