Effects of mannanoligosaccharide and fructooligosaccharide on the response of broilers to pathogenic Escherichia coli challenge.

1. The effects of mannanoligosaccharide (MOS, Bio-Mos, Alltech Inc.) on the growth performance and digestive system, particularly gut microflora, were tested and compared with fructooligosaccharide (FOS, Raftilose P95, Orafti) using 1-d-old birds in an Escherichia coli challenge model. The experiment lasted for 3 weeks and zinc bacitracin (ZnB) was used as a positive control. 2. Dietary MOS had positive effects on body weight gain (BWG) or/and feed conversion efficiency (FCE) of the challenged birds compared to the negative control at the end of weeks 1 and 3. Similar results were obtained for ZnB treatment. In contrast, FOS supplementation improved only the BWG of the challenged birds at 21 d of age. Within the unchallenged birds, a large improvement in BWG was noticed for FOS treatment at the end of the experiment, with the BWG of birds on ZnB and MOS treatments being intermediate. The FCE of the unchallenged birds was not affected by the dietary additives. 3. The addition of MOS reduced the number of mucosa-associated coliforms in the jejunum of the challenged birds on d 7. On d 21, FOS tended to increase the number of jejunal mucosa-associated lactobacilli in both the challenged and unchallenged birds. The number of Clostridium perfringens in the gut lumen was reduced by only ZnB. 4. Dietary MOS reduced the jejunal crypt depth of birds on d 7, regardless of the challenge. The FOS supplement did not affect the gut morphology, however, the concentration of lactic acid in the ileum was increased and, depending on the challenge, the intestinal pH was decreased by FOS at different ages. 5. In conclusion, the effects of MOS or FOS on the composition and activities of gut microflora and mucosal morphology of birds were related to E. coli challenge as well as the age of birds, which may be involved in the observed different growth-improving effects of the tested dietary additives.