Effects of Supplemental Xylanase, Cereal Grain Source, and Age on Caecal Volatile Fatty Acid Concentrations of Broilers from 14 to 42 Days of Age

Supplemental xylanase may be used in diet formulation to reduce diet cost, mitigate the antinutritive effects of arabinoxylans, increase energy utilization, and improve growth performance of broilers. Xylanase has been shown to partially depolymerize arabinoxylans, which can reduce intestinal viscosity, reduce nutrient encapsulation, and modulate the intestinal microflora of broilers (Choct et al., 1999; Bedford, 1995; Bedford and Cowieson, 2012). In addition, products of xylanase hydrolysis, arabinoxylo- and xylo-oligosaccharides, have been reported to stimulate a prebiotic effect, increasing broiler caecal fermentative capacity, and volatile fatty acid (VFA) production (Masey O’Neill et al., 2014). However, factors such as cereal grain source and bird age affect the mode of action of xylanase.

An experiment was conducted to assess the effects of supplemental xylanase, cereal grain source, and age on caecal VFA concentrations of Ross × Ross 708 male broilers during weekly intervals from 14 to 42 d of age. One thousand five hundred day-old chicks were randomly distributed into 60 floor pens (25 chicks/pen; 0.078 m²) and fed 1 of 4 dietary treatments from 1 to 14, 15 to 28, and 29 to 42 d of age with 15 replicate pens per treatment. Dietary treatments consisted of a 2 × 2 factorial arrangement with 2 cereal grain sources (corn- or wheat-based) and 2 supplemental xylanase inclusions (with or without) as the main factors. Caecal contents were collected and pooled from 4 broilers per pen at 14, 21, 28, 35, and 42 d of age for VFA analysis.

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 broilers fed the wheat-based diet with xylanase exhibited higher concentrations of butyric and total VFA than broilers fed wheat-based diet without xylanase. 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 acids than birds fed wheat-based diets from 14 to 42 d of age. Conversely, broilers fed wheat-based diets had higher (P < 0.05) concentrations of butyric acid at 28, 35, and 42 d of age compared with broilers 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 indicate that broiler caecal VFA concentrations are influenced by cereal grain source and bird age. However, inconsistent effects of xylanase supplementation on broiler caecal 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 warranted.