Responses in ileal and cecal bacteria to low and high amylose/amylopectin ratio diets in growing pigs

Dietary starch that escapes digestion in the small intestine may serve as a carbon source for bacterial fermentation in the distal intestine. This study aimed to compare the bacterial community in the ileal and cecal digesta of growing pigs fed diets with low (0.14, LR pigs) and high (0.43, HR pigs) amylose/amylopectin ratio. Pyrosequencing based on MiSeq 2000 platform showed that in ileum digesta, Bacteroidetes of LR pigs was markedly higher than that in HR pigs (P < 0.05). Megasphaera and Prevotella were the two most predominant genera in LR pigs, and Prevotella was significantly higher in LR pigs than in HR pigs (P < 0.05). Prevotella was predominant in cecal samples from both LR and HR pigs, although no significant differences were found between the two groups. In the ileum, Megasphaera elsdenii and Mitsuokella multacida were significantly (P < 0.01) higher in LR pigs along with an increase of acetate and butyrate concentrations. Halomonas pacifica, Escherichia fergusonii, and Actinobacillus minor which belong to class Gammaproteobacteria were significantly lower (P < 0.01) in HR pigs with a significant increase (P < 0.01) of Lactobacillus acetotolerans-like bacteria. Therefore, the changed bacterial community may lead to a transformation of microbial function, such as the alteration of fermentation mode which is showed on the change of microbial metabolites like the concentration of short-chain fatty acids (SCFAs), to a response to the switch of dietary composition, and in turn, to help host absorb and utilize nutrients efficiently. The increase of dietary amylose induced the reduction of conditioned pathogens which may probably be due to the increase of some probiotics such as Lactobacillus, thus reducing the risk of intestinal disease.