Seeder Model Challenge of Emerging Salmonella Infantis in Broilers: Potential of Organic Acid-Based Feed Additive in...

Salmonella Infantis is a recognized antimicrobial resistance threat, and in the compromised chicken gut, this pathogen penetrates weakened tight junctions, disrupts the microbiota balance, and triggers inflammation. This study evaluated the potential effects of a feed additive blend comprising short chain fatty acids including coated sodium and calcium butyrate, medium chain fatty acids, and phenolic compounds on broiler gut health and performance under a Salmonella challenge using a proprietary seeder model methodology. The foundation, led by a preliminary study as Part A, comprises a negative control and two treatment groups, ran to develop a seeder model, and 1056 day-old Ross 308 broiler chicks were allocated into three groups. On days 5-6, Salmonella Infantis 7570 was inducted via seeders in T2 (frozen strain) and T3 (live strain), while T1 remained unchallenged. No significant difference in infection development was observed between T2 and T3 (p > 0.05). In T1, Salmonella positivity checked via real time polymerase chain reaction (iQ-check II Biorad) remained below 50% at respective time points, indicating that complete isolation in the same room is not feasible. Henceforth, in the main experiment, Part B, 396 male day-old Ross 308 birds were randomly assigned to two further treatments: (1) a positive control group fed a commercial diet, and (2) a treatment group fed the same diet supplemented with 2.5 kg/t of an organic acid-based additive blend (Presan FY, Tilburg, The Netherlands) until day 28. On days 5 and 6, five birds per pen were orally inoculated with 10⁹ CFU/mL Salmonella Infantis 7570 obtained via Part A and placed as seeders in both treatments. A borderline tendency for lower Salmonella counts was observed in the treatment group on day 19 (p = 0.062). The control group had significantly higher lesion scores on day 13 (p = 0.0068), with no significant difference on day 19. Body weight was significantly higher in the treatment group on days 11 and 28 (p = 0.0157), with no difference on day 39 (p = 0.1857). Average daily gain improved significantly between days 11 and 28 (p = 0.0234), and feed intake was also significantly higher during this period (p = 0.0007). Feed conversion ratio showed a tendency to improve between days 5 and 11 (p = 0.0638). Overall, this study reveals that the seeder model can be adopted in Salmonella research, and the application of a blend showed a borderline tendency to reduce Salmonella counts, however significantly lower the lesion scores, thereby improving gut health in broilers under a Salmonella challenge.