A Bacillus-based direct-fed microbial impacted growth performance, immune cell presence, and in vivo Salmonella Enteritidis dissemination in growing broiler chickens.

Bacillus-based direct-fed microbials (DFMs) have previously improved broiler performance and pre-harvest food safety by reducing foodborne pathogens. Therefore, an experiment was conducted to determine the effects of a Bacillus-based DFM on performance and physiological recovery metrics post- Salmonella Enteritidis challenge in growing broiler chicks. 560 male Ross 308 broilers were wingbanded at hatch and distributed among 40 cages (14 chicks/cage). Chicks were allocated into one of two dietary treatment groups, control (CON) or MicroLife® Prime (MLP), ± 1 × 108 CFU Salmonella Enteritidis (SAL) inoculated at 7 d of age, for a total of 4 treatments: 1) CON (corn-soy) diet + sham gavage; 2) CON+SAL gavage; 3) MLP (500,000 CFU/g of feed) + sham gavage; or 4) MLP (500,000 CFU/g of feed) + SAL gavage. Growth performance was measured weekly and at sampling timepoints through study completion on day 21. At 4, 7, and 14 days post SAL inoculation (dpi), liver, spleen, and swab samples were collected for PCR and microbiology. Growth performance data were analyzed using SAS PROC ANOVA. Salmonella prevalence data were analyzed using SAS PROC FREQ chi-squared tests. At day 7 prior to challenge, MLP-fed birds tended to have a 7.75% heavier body weight (BW) than CON (p = 0.057), with a 10.37% improvement in BW gain. At 4dpi, MLP supplementation increased BW by 28.9 g, increased FI by 15.4 g, and improved FCR from 1.441 to 1.186 (main effect: p < 0.05). No Salmonella was present at baseline prior to inoculation. Cloacal swab SAL prevalence at 4dpi was significantly higher by 70% in CON+SAL vs. unchallenged treatments with 0% prevalence (p = 0.004), with MLP+SAL being statistically intermediate at 40% prevalence. Baseline splenic interleukin (IL)-17 was significantly upregulated two-fold due to MLP (p = 0.02). MLP downregulated IL-4 expression by 57% in baseline liver samples while increasing IFN-γ by 60% compared to control (P < 0.05), with a trend for MLP to reduce IL-17 expression by 41%. Feeding MLP improved BW and regulatory/ pro-inflammatory cytokine expression prior to challenge, with positive effects carrying over during SAL challenge.