Extent of Butyrate Metabolism by Bovine Ruminoreticulum Epithelium and the Relationship to Absorption Rate

Abstract Solutions containing acetate, propionate, and butyrate were placed into the ruminoreticulum of three calves in ten experiments to measure the extent to which butyrate, absorbed at different rates, is converted to ketone bodies by ruminoreticulum epithelium. In response to five different combinations of pH and concentrations of total volatile fatty acid in 18 liters of solution, absorption rates in millimoles per hour ranged from 170 to 600 for acetate, from 89 to 341 for propionate, and from 58 to 269 for butyrate. Specific absorption rates were in the order of butyrate>propionate>acetate at pH 4.8 and 6.0 but were about equal at pH 7.2. The extent of butyrate conversion to ketone bodies (calculated from portal-arterial concentration differences in butyrate, aceto acetate plus acetone, and yS-hydroxybuty-rate) averaged 49 (range 33 to 78)%. The extent of butyrate conversion was affected by pH and by concentration of volatile fatty acid in the ruminoreticulum and was negatively correlated to the rate of butyrate absorption. About three-fourths of the portal-arterial differences in ketone bodies were accounted for by β -hydroxybutyrate.