Portal and hepatic fluxes in sheep and concentrations in cattle ruminal fluid of 3-(4-hydroxyphenyl)propionic, benzoic, 3-phenylpropionic, and trans-cinnamic acids.

Extraction methods and HPLC procedures were developed for analysis of potential ruminal metabolites of dietary phenolics (reduced phenolics). Hepatic portal venous blood from wethers fed bromegrass, bermudagrass, ryegrass-wheat, and alfalfa hays also was analyzed for hippuric (HA), 3-(4-hydroxyphenyl)propionic (4OHPPA), benzoic (BA), 3-phenylpropionic (PPA), and t-cinnamic (CA) acids. Additionally, mesenteric arterial and hepatic venous blood was analyzed and, in conjunction with blood flow measurements, fluxes for portal-drained viscera (PDV) and liver were calculated. Ruminal fluid from four steers fed two levels of forage and two forage particle sizes in a Latin square design was analyzed for PPA and CA. 3-Phenylpropionic and benzoic acids were the most concentrated reduced phenolics identified in hepatic portal venous blood. Concentrations of PPA in ruminal fluid varied with ruminal disappearance of p-coumaric and ferulic acids. Additionally, hepatic portal venous concentrations of PPA were correlated (P < .05) with p-coumaric acid (r = .57) and ferulic acid (r = .67) intakes. Net release of PPA from PDV was observed, suggesting absorption of PPA from the gut. The liver removed PPA and BA with less efficiency. Given the relatively high concentrations of PPA in blood of ruminants, specific effects of this reduced phenolic on liver metabolism of ruminants should be assessed.