Effects of Supplemental Xylanase in Corn- and Wheat-Based Diets on Growth Performance and Cecal Volatile Fatty Acid Concentrations of Broilers during a Six-Week Production Period
McCafferty, Klinton Wesley
Type of DegreeMaster's Thesis
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Supplemental xylanase has increasingly become an important part of diet formulation due to its ability to mitigate the anti-nutritive effects of arabinoxylans, increase energy utilization, and improve growth performance of broilers. Xylanase partially depolymerizes arabinoxylans, which can reduce intestinal viscosity, reduce nutrient encapsulation, and modulate intestinal microflora in broilers. Additionally, products of xylanase hydrolysis, arabinoxylo- and xylo-oligosaccharides, have been reported to stimulate a prebiotic effect, increasing broiler cecal fermentative capacity and volatile fatty acid (VFA) production. However, factors such as inclusion concentrations, cereal grain source, and bird age have been observed to affect xylanase’s mode of action and magnitude of response. Therefore, 2 experiments were conducted to assess the energy-sparing effects of supplemental xylanase in corn- and wheat-based diets on Ross × Ross 708 male broiler growth performance and cecal VFA concentrations during a 6-week production period. Experiment 1 evaluated effects of various supplemental xylanase concentrations (0, 12,000, and 24,000 BXU/kg) in corn- and wheat-based diets formulated with reduced apparent metabolizable energy concentrations on broiler growth performance and cecal VFA production from 1 to 40 d of age. From 1 to 26 d of age, cereal grain source (P < 0.05) affected broiler growth performance with birds receiving corn-based diets having increased body weight gain, increased feed intake, and lower feed conversion ratio than those fed wheat-based diets. However, no dietary treatments (P > 0.05) differences were observed with cumulative growth performance. Cereal grain source (P < 0.05) influenced propionic, isobutyric, butyric, and isovaleric concentrations at 26 and 40 d of age with birds receiving corn-based diets having higher (P < 0.05) concentrations of propionic, isobutyric, and isovaleric, and lower (P < 0.05) concentrations of butyric than birds fed wheat-based diets. These results demonstrated that cereal grain source influenced broiler cecal VFA concentrations. However, supplemental xylanase did not influence broiler growth performance or cecal VFA concentrations. Experiment 2 evaluated effects of age and supplemental xylanase in corn- and wheat-based diets on cecal VFA production during weekly intervals from 14 to 42 d of age. Cereal grain source and supplemental xylanase interacted (P < 0.05) to affect butyric (14 and 21 d of age) and total VFA (21 d of age) concentrations. Broilers fed corn-based diets with and without xylanase and wheat-based diet with xylanase exhibited higher concentrations of butyric and total VFA than those fed wheat-based without xylanase. Main effects of cereal grain source (P < 0.05) influenced propionic, isobutyric, butyric, isovaleric, valeric, and isocaproic acid concentrations at 14, 21, 28, 35, and 42 d of age. Broilers fed corn-based diets had higher (P < 0.05) concentrations of propionic, isobutyric, isovaleric, valeric, and isocaproic than birds fed wheat-based diets from 14 to 42 d of age. However, broilers fed wheat-based diets had higher (P < 0.05) concentrations of butyric acid at 28, 35, and 42 d of age compared with those fed corn-based diets. All individual and total VFA concentrations increased (P < 0.05) linearly from 14 to 42 d of age. Age and cereal grain interactive effects (P < 0.05) were observed with propionic, isobutyric, butyric, isovaleric, and valeric acid concentrations. These results indicated that broiler cecal VFA concentrations are largely influenced by cereal grain source and bird age. However, inconsistent effects of xylanase supplementation on broiler growth performance and cecal VFA concentrations demonstrate that future research evaluating factors such as substrate availability, gastrointestinal environment and age, xylanase inhibitors, microflora composition, immunological and stress conditions, and health are needed.
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