Effect of β-mannanase inclusion on growth performance, ileal digestible energy, and intestinal viscosity of male broilers fed a reduced-energy diet

The objective of the current trial was to investigate the effect of beta-mannanase sourced from Bacillus subtilus on broiler performance, ileal digestible energy, and intestinal viscosity. A randomized complete block study was conducted utilizing a total of 1,800 one-day-old Cobb 500 male broilers distributed among 3 treatments with 15 repetitions; n = 40 broilers/pen on new pine shavings. The experimental design consisted of 3 dietary treatments: positive control (PC), negative control (NC) containing 97 kcal/kg AME less than the PC, and negative control + beta-mannanase. Beta-mannanase was included at 453.6 g/ton with sand being added to the NC diet at 453.6 g/ton. Diets were corn and soybean meal based with the inclusion of DDGS and phytase and pelleted at 75C. Production parameter (feed intake, BW, BW gain, and mortality corrected FCR) comparisons were made across treatment groups on a weekly basis. The PC fed broilers maintained a heavier average BW (P < 0.05) when compared to the NC between d 14 and 42, indicating that the reduction in energy was sufficient to reduce average BW. With the inclusion of beta-mannanase in the NC, broilers were able to achieve similar performance when compared to the PC during this period. The PC diet maintained a lower mortality adjusted FCR (P < 0.05) when compared to the NC during wk 1 and 2, while the inclusion of beta-mannanase produced similar results as the PC. The PC fed broilers exhibited an improved cumulative FCR (P < 0.05) compared to the NC diet throughout the duration of the experiment, while the beta-mannanase inclusion resulted in a similar FCR as compared to the PC fed broilers. Dietary treatment did not significantly influence intestinal viscosity or ileal digestible energy on d 17 or 37 of sampling. Overall, beta-mannanase inclusion in a reduced-energy pelleted diet eliminated losses in growth performance.