Effects of Aspergillus sp. supplementation with or without xylanase on growth performance, nutrient digestibility,...

This study aimed to evaluate the in vivo enzyme activity of Aspergillus sp. in the presence and absence of supplemental xylanase enzyme and determine its effect on the growth performance, nutrient digestibility, and microbiome of broilers. A total of 120 male Cobb® 500 broilers were randomly assigned to 12 replicate cages across 4 treatments (n = 3 per treatment) and raised till 21 days. The dietary treatments were arranged in a 2 × 2 factorial design with xylanase and Aspergillus sp. addition as the main factors. The xylanase was included at 520 U/kg and Aspergillus sp. was supplemented as conidiospores at 6.4 × 10⁷ CFU/ kg of the basal diet by replacing sand. The total feed intake and the total body weight per cage were recorded weekly. The total feed intake and total excreta output were recorded on d 20 to calculate apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn). The jejunum, ileum, and ceca were collected on d 14 and d 21 for quantitative PCR and microbiome analyses. The growth performance and nutrient digestibility data were analyzed by two-way ANOVA in a completely randomized design using SAS 9.4 (SAS Inc., Cary, NC) with statistical significance declared at P < 0.05. The treatments did not have a significant effect on the nutrient digestibility and growth performance of the broilers. However, a trend was observed for the interaction between xylanase and Aspergillus sp. on the average daily gain (ADG) and the final body weight gain (FBWG) of broilers during d 0-21 (P = 0.099). Microbiome analysis revealed no major shifts in overall community structure, although several taxa exhibited small but statistically significant differences in response to dietary supplementation with xylanase and/or Aspergillus spores. AI-enabled genome and literature searches indicated that taxa enriched under enzymatic treatments commonly possess metabolic functions related to the fermentation of complex carbohydrates for the production of short-chain fatty acids. The results indicate that the effects of Aspergillus sp. on nutrient digestibility and utilization by broilers are influenced by the presence of exogenous enzymes and dietary substrates and are further modulated by the gut microbiome. Supplemental Aspergillus sp. conidiospores provided similar and numerically greater improvements in FBWG and exerted significant effects on the select members of the gastrointestinal microbiome.