Abstract: The influence of different sources of starch on average daily gain and net portal absorption of nutrients by portal vein-drained organs in growing pigs fed different sources of starch has been reported in this study. The daily gain was greater for the pigs fed the starch from corn and brown rice than that of brown stick rice (P<0.05) and resistant starch (P<0.01). The portal vein absorptions of glucose and total amino acid were 17.84 and 5.93 g/100 g feed intake respectively which were lower (P<0.05) than those of the pigs fed the corn, brown rice and brown stick rice. However, all of the portal absorptions of amino acids were much lower than the ileal digestibility of amino acids. There was a closed relationship (P=0.029 5) between average daily gain with net portal absorption of total amino acids in growing pigs