Splanchnic metabolism of short-chain fatty acids in the ruminant

The unique digestive system of ruminants has major impacts on their energy metabolism because carbohydrates are largely fermented and only to a small extent digested by host enzymes. Shortchain fatty acids (SCFA) are produced during fermentation in the ruminant forestomachs and quantitatively SCFA are the most important substrates for ruminant energy metabolism. The central dogma of ruminant nutritional physiology has been that gut epithelia have a large metabolism of SCFA and that SCFA are available to other tissues in considerably lower amounts than ruminal production would suggest. A series of papers published since the IX ISRP question the traditional view on SCFA metabolism and it is concluded that the forestomach epithelia contrary to our previous understanding, do not metabolize extensive amounts of acetate and propionate. The forestomachs of ruminants have a high affinity for butyrate and valerate and the physiology of gut epithelial and hepatic metabolism of SCFA is discussed in this context.