The effects of mesenteric venous infusion of acetate, propionate and butyrate mixture (20.3, 40.5 and 81.0μmol kg^-1 min^-1 over 4h) on the secretion of GH was examined to investigate the effects of an increase in portal volatile fatty acids (VFA) on GH secretion in relation to inhibition of GH secretion after feeding in sheep. The mesenteric venous infusion at the rate of 40.5μmol kg^-1min^-1 increased the portal plasma VFA concentration within the approximate physiological range after feeding. Plasma GH was noticeably suppressed only at the infusion rate of 81.0μmol kg^-1 min^-1 and the change in the mean concentration from the base line was significantly less than in the control. Although GRF injection rapidly increased plasma GH, the change in the mean concentration from the base line tended to suppress only at the infusion rate of 81.0μmolkg^-1 min^-1. Plasma FFA was suppressed in a dose-dependent manner after VFA infusion. The change in the mean concentration from the base line was significantly suppressed only at the infusion rate of 81.0μmol kg^-1 min^-1 relative to the control infusion, but plasma glucose was unchanged by VFA infusion. It is concluded that because the increase in the portal plasma VFA concentration within the range of feeding did not suppress GH secretion, VFA absorbed by the digestive tract may not play a significant role in suppressing GH secretion after feeding in sheep.