Abstract
Numerous studies have reported the beneficial effects of supplemental xylo-oligosaccharides (XOS) on broiler performance and nutrient utilization. These effects are attributed to their prebiotic action, directly fueling beneficial bacterial species, and their ability to stimulate fibre-degrading bacteria in the gastrointestinal tract. Commercial XOS products typically contain mixtures with varying degrees of polymerisation (DP), ranging from xylobiose (X2) to xylohexaose (X6). This study aimed to determine the optimum DP range of XOS for broiler chickens. Two trials were conducted using 0 d-old Cobb 500 broilers (300 per trial, 60 birds per treatment, initial body weight 45.80 ± 0.15 g) fed wheat-based diets over 35-d period as three phases (starter d 0-12, grower d 12-23, and finisher d 23-35). In both trials, birds were fed one of five XOS treatments (150 g/tonne); no XOS (control), low-DP XOS, medium-DP XOS, high-DP XOS, or a standard commercial XOS mixture. In Trial 1, the XOS treatments were fed without xylanase, and in Trial 2 the XOS treatments were fed with xylanase (16,000 birchwood xylanase units [BXU]/kg). In Trial 1, birds fed the high-DP XOS had significantly lower feed conversion ratio corrected for mortality (cFCR) at d 0 to 35 (P < 0.001) compared to birds fed the control and medium-DP XOS treatments. Additionally, birds fed the control diet presented higher caecal concentrations of branched-chain fatty acids (iso-butyric and iso-valeric acids) compared to those fed the high-DP XOS (P = 0.025 and P = 0.035, respectively). In Trial 2, birds receiving the high-DP XOS showed improved cFCR compared to those fed the low-DP XOS (P = 0.037). Low-DP XOS fed birds also presented increased caecal Enterobacteriaceae abundance compared to those fed the control diet, medium-DP XOS or commercial XOS treatments (P = 0.008). In conclusion, supplementation with high-DP XOS was more effective in improving feed efficiency and modulating caecal fermentation than feeding no XOS or low-DP XOS.