Effects of mannanoligosaccharide in broiler chicken diets on growth performance, energy utilisation, nutrient digestibility and intestinal microflora.

1. A study was undertaken to evaluate the effects of mannanoligosaccharide (MOS, Bio-MOS, Alltech Inc.) on the growth performance, energy utilisation, nutrient digestibility and intestinal microflora of birds given a sorghum-wheat based diet. Two MOS levels (1 and 2 g/kg) were included in the diet. 2. Inclusion of MOS at both levels in the diet improved the apparent metabolisable energy (AME) values of the diet. However, these effects were not as pronounced as those of zinc bacitracin (ZnB) treatment. Dietary ZnB also significantly improved the net energy value of the diet. No significant differences between the different levels of MOS were noticed in the growth performance, AME and net energy values of the diet. Compared to the negative control, inclusion of 2 g/kg MOS tended to improve feed conversion efficiency (FCE) in the starter phase. 3. Dietary MOS did not affect the apparent total tract digestibility of nutrients compared to the negative control. In contrast, ZnB significantly improved the protein digestibility and tended to increase the starch digestibility. The addition of MOS reduced the concentration of arabinose in the soluble non-starch polysaccharides (NSP) fraction in the excreta of birds; whereas, the concentrations of individual sugars in the insoluble NSP and free sugar fractions were increased by ZnB. 4. A decrease in the populations of lactobacilli and coliforms in the ileal and caecal lumen was observed for MOS and ZnB treatments. Correspondingly, pH and microbial fermentation in the gut was altered. The addition of MOS tended to reduce the coliform load at the gut mucosa. 5. Results from the current study suggest that MOS can improve the apparent energy utilisation of the diet and tend to improve FCE of birds in the first three posthatch weeks, which may be partly related to the modulatory effects of MOS on the gut microflora.