| Three experiments were conducted to investigate the influence of different dietary starch sources on the performance of growing pigs and the relative mechanisms. Base on the comparison of different feeding effect of dietary starch sources, starch in vivo digestion and absorption as well as it's effect on amino acids digestion and utilization was further studied. The reasons for the different feeding effect of dietary starch sources were elucidated from both digestive tract and portal-drained viscera absorption aspects.Trial 1 The effect of dietary starch sources on the performance , nutrients digestibility and blood biochemical parameters in growing pigsA feeding trial covered 30ds and a 5 × 5 Latin square design metabolism experiment using 45 20 ±0.642kg duroc × landrance × yolkshire cross breed pigs were conducted to study the effect of dietary starch sources on the performance and nitrogen metabolism. 4 iso-nitrogen, iso-energy and iso-starch diet were formulated using Maize, Brown rice. Stick rice and Resistant starch (Hi-maize-1043) as starch sources, as well as an nitrogen free diet was also formulated to determinate the endogenous nitrogen losses. The results showed that the body weight gain of Maize group was 719.52g, which wasl4.69%, 11.92% and 3.03% higher than Resistant starch, Stick rice and Brown rice group respectively. While the feed conversion (feed consumption/ body weight gain) was 1.64%, 12.46% (p<0.05) and 0.5% lower than Resistant starch, Stick rice and Brown rice group correspondingly. The lowest fecal crude protein apparent and true digestibility were found in Resistant starch group, which were 10.23%, 12.76%, 12.42% and 9.64%, 12.11%, 11.73% (p<0.05) lower than Maize, Stick rice and Brown rice group, and also the digestibility of energy and dry matter of Resistant group were lower than other groups. When compared with other groups, Resistant starch group excreted the most fecal nitrogen (p<0.05), while Stick rice had the highest urinarynitrogen excretion (p<0.05), but the largest whole body nitrogen retention was found in Maize group. The results of blood biochemical parameters analysis indicated that, the change of post-prandial blood glucose, insulin concentration and insulin/ glucose in Resistant starch was stable , while other groups had larger fluctuation, lh after the meal which reached the pinnacle, among them Stick rice group had the highest blood glucose, insulin concentration and insulin/ glucose in post-prandial lh, they were 1.21mg/ml, 52.35(u.U/ml) and 43.27(u U/umol) respectively, and were significantly higher than other groups (p<0.05).Trial 2 The effect of dietaiy starch sources on amino acid digestibility and micnobinl amino acids content in ileal digesta of growing pigsFive duroc X landrance X yolkshire cross breed male pigs fitted with permanent T cannulation were used in a 5 X 5 Latin square design experiment to test the effect of different starch sources on ileum digestibility of dietary starch and amino acids. The results showed that the starch digestibility of Resistant starch group was 83.07%, which was significantly lower than Maize, Brown rice and Stick rice group (p<0.05). The ileum apparent and true digestibility of Asp, Glu, Ser, His, Thr, Arg, Tyr, Meth, Phe, He, Leu and Lys in Resistant starch group were significantly lower than Maize and Brown rice group (p<0.05). The ileum apparent digestibility of Ser, Ala, Tyr in Stick rice group was lower than Maize and Brown rice group (p<0.05), while the ileum true digestibility of His was higher than other groups. Bacterial amino acids proportion of ileum digesta of all groups change in the range of 25.43% (Maize group) —45.09% (Resistant starch group), among them the proportion of Asp, Glu, Ser and Lys in Resistant starch group were significantly higher than Maize group(p<0.05), but Tyr was lower than Maize group (p<0.05). The proportion of Arg in Brown rice group was significantly higher than Resistant starch group, while Ala and Leu were lower (p<0.05), the proportion of Ala and Leu in Stick rice group was also significantly lower than Resistant starch group (p<0.05).Trial 3 The effect of dietary starch sources on amino acids portal flux and balance in growing pigsFour duroc X landrance X yolkshire cross breed male pigs fitted with permanent catheters in the portal vein, mesenteric vein and in the carotid artery were used in a 4X 4 Latin square to measure the different effect of dietary starch sources on net portal absorption of blood glucose, volatile fatty acids (VFA), amino acids and lactate in growing pigs. When calculated as per lOOg feed intake, 8h post- prandial Maize group portal vein net absorbed 27.52g glucose, which was 54.26%, 7.88% and 1.55% higher than Resistant starch, Stick rice and Brown rice respectively. Stick rice group absorbed 2.52g lactate and it was significantly higher than other groups (P<0.05). In Resistant starch group the portal vein absorbed blood ammonia was (5.36g) lower than other groups (PO.05), while the absorbed VFA (403.87mmol) was significantly higher than Maize, Brown rice and Stick rice group. Portal vein net absorbed total amino acids of Resistant starch, Maize, Brown rice and Stick rice group were 5.93g, 8.89g, 8.77g and 7.83g, the lowest net portal vein absorption was found in Resistant group. The proportion of net absorbed total amino acids in ileum apparent and true digested amino acids were 52.70% and 48.39%, which were lower than 67.66%, 65.83%. 63.62% and 63.76%, 61.80%, 59.18% of Maize, Brown rice and Stick rice group (PO.05). The proportion of essential amino acids in absorbed total amino acids of Resistant starch group was 50.0% it was also lower than 57.43%, 56.64%, 57.74% of Maize. Brown rice and Stick rice respectively. Portal vein net absorbed Glu, Ser, His, Arg, Ala, Tyr, Metli, Val, Phe, He, Leu and Lys of Resistant starch group and His, Arg, Tyr, Val, Meth, Lys and Leu of Stick rice were lower than Maize and Brown rice group (P<0.05). There are no significant difference between Maize and Brown rice group for most net absorbed amino acids, but His, Lys and Leu in Maize group were higher (P<0.05), while Arg was lower than Brown rice group (P<0.05). The balance pattern of portal vein net absorbed amino acids of Maize group was better than other groups.
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