Metabolic response of the gastrointestinal tract of turkeys to diets with different levels of mannan-oligosaccharide.

Different levels of dietary mannan-oligosaccharide (MOS) administered for 16 wk to commercial male turkeys were evaluated for their efficacy on performance and on microbial activity in the digestive tract. The following levels of MOS were used in a diet: low (0.1% during the entire study), medium (0.4 and 0.2% in the first and second 8-wk periods, respectively), and high (1.0 and 0.4% in the first and second 8-wk periods, respectively). After 16 wk of experimental feeding, the diet intake was similar in all groups examined, whereas the live BW was significantly higher in groups with medium and high levels of MOS compared with the control group and birds fed a diet containing a low level of mannan. The pH of ileal and cecal contents were unaffected by dietary treatments. The highest ammonia concentration in the cecal digesta was associated with a low dose of mannan in a diet, and the concentration was reduced to the control level when both higher doses of MOS were used. Bacterial enzyme activity remained unaffected by experimental treatments. The concentration of short-chain fatty acids in the ceca decreased with increasing amounts of MOS in a diet, especially in the case of acetate. Dietary MOS did not significantly affect the cecal populations of Bifidobacterium and Lactobacillus. The population of cecal Escherichia coli was decreased, especially by the medium and high experimental treatments.