Effects of isomalto-oligosaccharides on broiler performance and intestinal microflora.

Dose effects of dietary isomalto-oligosacchrides (IMO) on broiler growth performance and characteristics of the intestinal microflora were compared. Three hundred sixty male broilers were randomly allotted to five treatments, with eight replicate pens per treatment and nine chicks per pen. Chicks were fed either a basal diet (control) or the basal diet plus 0.3, 0.6, 0.9, or 1.2% IMO. All chicks had access to feed and water ad libitum during the 7-wk experiment. At the end of the experiment, eight chicks per treatment were randomly chosen to measure the thymus index. Additionally, six birds per treatment were randomly selected to determine viable bacterial counts of Lactobacillus, Escherichia coli, and total aerobes in the digestive tract. The digesta of all the killed birds were also used to measure short-chain fatty acid (SCFA) levels. The results indicate that IMO enhanced growth performance during the initial 3 wk, but no further effects were detected during the latter 4 wk of the experiment. Isobutyrate level in crop content and acetate level in duodenum digesta were decreased by supplementation with IMO (P < 0.05). Isovalerate level in duodenum digesta was decreased in the 0.3 and 0.6% IMO groups (P < 0.001), whereas the jejunum butyrate and isobutyrate levels of the 0.3% IMO group were higher than in other groups (P < 0.05). The facultative microflora of the crop and cecum were not affected by IMO supplementation. However, the thymus index was increased significantly in chicks consuming diets containing 0.3% IMO.