A total of 384 Cobb 500 male broiler chicks were used in a 21-day experiment to study xylanase and protease influence on digesta oligosaccharides profile and nutrient utilization responses in broilers receiving different dietary levels of fiber (F) and protein (P). A total of 16 diets arranged in 2×2×2×2 factorial for effects of fiber (low, L or high, H), protein (L or H), xylanase (without or with), and protease (without or with) were used. The 16 diets consisted of four basal diets: LFHP, LFLP, HFHP and HFLP supplemented with xylanase or protease individually or in combination. Wheat bran was used to increase the dietary fiber content and the HF diets had lower ME. All the diets were supplemented with phytase at 500 FTU/kg. Birds were allocated to the 16 dietary treatments in a randomized complete block design on day 0 of age. Each treatment had 6 replicates with 4 birds per cage. Jejunal, ileal digesta and excreta were collected on d 21. The concentration of oligosaccharides in jejunal digesta was analyzed by matrix- assisted laser desorption ionization mass spectrometry analysis. The data were analyzed by the mixed model procedure of JMP Pro 14 for a randomized complete block design and a factorial treatment arrangement. There were no 4-way interactions for jejunal oligosaccharides (pentoses, Pent; and hexoses, Hex) level response. Birds fed HF diet had higher (P < 0.05) digesta concentrations of (Hex)5, (Pent)5 and (Pent)6, whereas enzyme supplementation had no effect. There was significant (P < 0.05) fiber × xylanase × protease interaction explained by the digesta concentrations of (Pent)3 and (Pent)4 being greatest (P < 0.05) in protease-only-supplemented HF diets whereas in the LF diets, combination of xylanase and protease produced greatest (Pent)3 and (Pent)4. There was no significant 4-way interaction for any digestibility parameter measured. There was significant (P < 0.01) fiber × xylanase × protease interaction for ileal DM and nitrogen digestibility. There was significant (P < 0.01) protein × xylanase × protease interaction for AMEn. The interaction is explained by lack of enzyme effect on AMEn in birds fed LP diets. In contrast, in birds fed HP diets, individual enzyme supplementation decreased AMEn (P < 0.05) whereas xylanase and protease combination increased (P < 0.05) dietary AMEn.
In conclusion, of all the factors investigated, dietary fiber level had the greatest effect on increasing digesta concentration of pentose and hexose oligosaccharides whereas the enzyme effects are less pronounced due to overlapping interactions. Additional studies are ongoing to further characterize the effect of the enzymes on oligosaccharides profile along the digesta tract of broilers.