Effect of a Bacillus-based probiotic on fecal shedding and cecal colonization of Salmonella Enteritidis in laying hens

Abstract

This study was conducted to evaluate a Bacillus-based probiotic to reduce Salmonella Enteritidis (SE) infection in Hy-Line W-36 hens at 24 weeks of age. The hens were assigned to four treatment groups: non challenged with basal diet (NC); challenged with basal diet (PC), PC + probiotic at 1 × 10⁶ CFU/kg (PRO1), and PC + probiotic at 2 × 10⁶ CFU /kg (PRO2). The probiotic used was a combination of five strains of Bacillus spp. Birds were adapted to the experimental diets for one week after which challenged birds were orally gavaged for two consecutive days with approximately 1 × 10⁹ colony-forming units (CFU) of nalidixic acid-resistant SE. Feed and water were provided ad libitum throughout the experiment. Fecal samples were collected on 3-, 7- and 14-days post inoculation (dpi). Cecal contents were collected aseptically on 7 and 14 dpi. Both fecal and cecal samples were plated on xylose lysine tergitol 4 (XLT4) plates with 200 ppm nalidixic acid using the direct plate method. Fecal samples were further enriched as per the National Poultry Improvement Plan procedures on tetrathionate (TT) and Rappaport Vassiliadis (RV) broth. Data were log-transformed and analyzed using the PROC GLIMMIX procedure of SAS 9.4. In the Ceca, PRO1 reduced the concentration of SE by 0.90 logs at 7 dpi (P=0.046). Although at 14 dpi both PRO1 and PRO2 decreased SE by 0.40 and 0.60 logs in the ceca (P=0.08). Similarly at 14 dpi, PRO1 and PRO2 reduced SE concentration by 0.80 and 0.75 logs in fecal samples using direct plating (P=0.032). Similarly, we observed that RV and TT enrichment increased SE counts by 1.5 and 2.6 logs, respectively at 14 dpi (P<0.001). This indicates that the enrichment method increased the SE enumeration as compared to direct plating method. There were no differences in SE fecal shedding at 0, 3, and 7 dpi by direct platting or enrichment methods. In conclusion, Bacillus-based probiotics have the potential to reduce SE in both ceca and fecal samples from laying hens.