EFFECT OF ORAL-ADMINISTRATION OF FOLATE SOURCES ON PLASMA FOLATE LEVELS IN PIGS - COMPARISON BETWEEN REDUCED AND OXIDIZED FORMS OF FOLATE

Two experiments were conducted to evaluate the response of plasma fola te levels after oral administration of oxidized or reduced forms of fo lates, using seven Gottingen minipigs. Plasma folate levels, tetrahydr ofolate (THF) and 5-methyltetrahydrofolate (5CH(3)-THF), were determin ed by high-performance liquid chromatography with electrochemical dete ction. In exp. 1, the absorption of the oxidized form of folate [(synt hetic folic acid(FA)] and the reduced forms of folate (5-formyltetrahy drofolate (5HCO-THF), liver powder and digested bacterial cell powder (DBCP) were evaluated by measuring changes in plasma folate levels aft er a single oral administration. Liver powder and DBCP contained much reduced forms of folate. The administration of the reduced form of fol ates increased plasma THF levels while the levels of plasma THF and 5C H(3)-THF decreased after FA administration. In exp. 2, plasma folate l evels were measured after long-term oral administration of FA for 30 d . Immediately after the beginning of the administration, the levels of both THF and 5CH(3)-THF decreased significantly and remained at a low level during the 30-d administration. Supplementation of sow feed wit h FA has been recommended in many countries improving reproductive per formance. The present study, however, suggests that the oral administr ation of an oxidized form of folate, FA, may not be as effective as pr eviously thought, and the reduced forms of folate might be preferable for the supplementation of pig feeds.