RUMEN INVOLVEMENT IN SHEEP TANNIC-ACID METABOLISM

Tannic acid (TA) metabolism was studied in sheep after po, intra-aboma sal and ip administration. TA and its phenolic metabolites in ruminal fluid, abomasal fluid, plasma and urine were determined using high-per formance liquid chromatography at various intervals post-dosing. After po administration, gallic acid (GA) and pyrogallol (PYR) were present in ruminal fluid and plasma, and GA, PYR and 4-0-methyl gallic acid ( 40MGA) were found in urine: The concentration of GA in ruminal fluid a nd urine gradually decreased after dosing, while PYR concentration con tinued to nse. By contrast, after intra-abomasal dosing, GA and ellagi c acid (EA) as well as TA were found in abomasal fluid, GA, 40MGA, EA and TA were present in plasma, and GA, 40MGA and PYR were in urine. Th e latter 3 metabolites were also detected in the urine after ip admini stration of TA. The plasma concentration of TA after intra-abomasal ad ministration was significantly correlated with liver necrosis, and PYR concentration in ruminal fluid following po administration was signif icantly correlated to blood methemoglobin level. It was concluded that the methemoglobinemia seen in sheep given TA po is caused by high lev els of the phenolic metabolite PYR, which is produced in the rumen. Li ver and kidney necrosis, seen in sheep given TA directly into the abom asum, appears caused by unmetabolized TA rather than by metabolites.