Feeding a Double Dose of Xylanase Improves Feed Conversion in Broilers Fed Corn-Based Diets, but not Wheat-Based Diets

Wheat has traditionally been the target substrate ingredient for xylanase application, due to its high arabinoxylan content causing increased digesta viscosity. However, numerous studies have highlighted the benefits of supplementing non-viscous corn-based diets with xylanase, on broiler performance and energy, protein and dry matter digestibility (Rabello et al., 2021; Stefanello et al., 2016). This is thought to be attributable to production of prebiotic xylo-oligosaccharides (XOS) as a consequence of xylanase hydrolysing dietary xylan. The hypothesis of this study was that increasing the dose of xylanase supplemented into both commercial-type corn- and wheat-based broiler diets would increase bird performance and reduce excreta moisture content, through heightened XOS production and reduced digesta viscosity. Cobb 500 mixed-sex broilers (n =360) were distributed into 36 pens, (10 birds per pen, 9 pens per treatment) and fed either a commercial-type corn- or wheat- based diet, supplemented with either a commercial recommended dose of xylanase (16,000 BXU/kg), or a double dose of xylanase (32,000 BXU/kg) (Econase XT 5P, AB Vista, Marlborough, UK). Diets were fed as three phases, Starter (d0-12), Grower (d12-23) and Finisher (d23-35). Birds and feed were weighed on arrival (d0) and on d12, 23 and 35, and these values were used to calculate feed conversion ratio corrected for mortality (cFCR). Fresh excreta samples were collected per pen on d12, 23 and 35 and dry matter content measured.

The lack of significant effect of the double xylanase dose on cFCR in birds fed the wheat-based diet suggests the commercial dose was sufficient at eliminating the anti-nutritional effects of the dietary xylan. Wheat-based diets also contain more fermentable xylan compared to corn-based diets, signifying the microbiota in wheat-fed birds contains more xylan-degrading bacteria species, so is better adapted at utilising dietary xylan. This was particularly apparent in the young birds, with lower cFCR value at d0-12 seen in birds fed the wheat- compared to corn- based diet (P < 0.001). The double xylanase dose did however increase excreta dry matter content at d35 in birds fed the wheat-based diet (P = 0.002), presenting increased xylan degradation. The positive effects of double xylanase dose in birds fed the corn-based diets suggests heightened production of XOS and solubilisation of xylan, which stimulated xylan-degrading bacteria and provided fuel for beneficial probiotic bacteria species. This study suggests that there may be benefits to supplementing higher xylanase doses, particularly in corn-based diets.

ACKNOWLEDGEMENTS: The authors are grateful for financial support from AgriFutures Australia Chicken Meat Program.