Determinants and effects of postileal fermentation in broilers and turkeys part 2: cereal fibre and SBM substitutes

Postileal fermentation in the gastro intestinal tract of poultry is affected by the main raw materials used during feed formulation, for example cereal grains, rapeseed meal, soybean meal, lupin seeds. Since cereal grains are the main source of dietary non-starch polysaccharides, including the viscous water-soluble fraction, their quality determines the rate of postileal fermentation. The supplementation of poultry diets with selected enzymes, mostly xylanase and beta-glucanase, suppresses fermentation in the upper gastro intestinal tract, and enhances the process in the caecum. Due to relatively high concentrations of raffinose family oligosaccharides in soybean meal, diets rich in that raw material may stimulate gut fermentation and decrease the growth performance of young birds. Rapeseed meal and lupin seeds, used as partial substitutes for soybean meal, affect fermentation processes in the gastrointestinal tract of poultry to a low degree, as compared with a soybean-based diet. Sunflower meal, even at low inclusion levels (14%), reduces the synthesis of caecal short chain fatty acids, probably due to an increase in lignified fibre in the diet.