Comparative efficacy of a Bacillus-based direct fed microbial and an antibiotic on performance and intestinal morphology of broiler chickens

    

Broiler chickens from commercial rearing facilities are subjected to a variety of stressors that increase disease susceptibility and reduce growth. Direct-fed microbials (DFM) can be employed to introduce beneficial bacteria to the digestive tract of poultry and through diverse mechanisms boost performance. The present study was conducted to evaluate the effect of supplementing broiler diets with DFM or bacitracin methylene disalicylate (BMD) on performance and intestinal morphology using a complete randomized design of 3 treatments including negative control (NC, basal diet), positive control (PC, basal diet + BMD at 55 ppm), and the basal diet + Novela® ECL DFM (United Animal Health, US) at 3.68x10⁵  cfu/g of feed (NECL). Each treatment included 10 replicate floor pens (used litter) with 40 male broilers per pen. All experimental diets were formulated based on corn and soybean meal. The diets were pelleted and offered ad libitum. The feeding program consisted of 3 dietary phases (starter 0-14 d; grower 14-28 d; finisher 28-42 d). Feed intake, body weight (BW), body weight gain (BWG), and FCR (corrected for mortality) were determined at the end of each feeding phase. Five birds per treatment were randomly selected and ileum samples were taken to evaluate villus height (VH), crypt depth (CD), and villus height/crypt depth ratio (VH:CD) at 28 days of the trial. Data were subjected to one-way ANOVA and means were separated using Fisher’s LSD (P< 0.05). Cumulatively at the end of the grower phase (0-28 d) both PC and NECL had increased (P=0.003) BW and BWG compared to NC. FCR improved (P< 0.001) by 4.5% and 3.7% for PC and NECL respectively, compared to NC. Although not statistical, numerical improvements were observed in both VH (P=0.131) and CD (P=0.103) for PC and NECL compared to NC, leading to a numerical improvement in VH:CD (P=0.792) for NECL compared to both the NC and PC. Cumulatively after 42 d, FCR was adjusted to a common BW of 2.94 kg (C-FCR). C-FCR was improved (P< 0.001) by 3.9% and 2.7% for PC and NECL respectively, compared to NC, and were not different (P> 0.05) from each other. In conclusion, the dietary supplementation of DFM to broiler diets improved cumulative growth performance and yielded similar results to the antibiotic BMD.

Key Words: Bacillus, broiler, antibiotic, direct-fed microbial, performance.