Effect of a Saccharomyces cerevisiae Postbiotic Feed Additive on Salmonella Enteritidis Colonization of Cecal and Ovarian Tissues in Directly Challenged and Horizontally Exposed Layer Pullets

Simple Summary In an era of increasingly complex global trade, continual evolution of production practices, and emerging threats from antibiotic resistance, new strategies for maintaining the health and performance of poultry flocks remain critical along with reducing risk from foodborne pathogens such as Salmonella Enteritidis (SE). Natural feed-additive technologies, often referred to as antibiotic alternatives, may play a key role. In this study, layer pullets were fed a control diet with or without a postbiotic feed additive and subsequently challenged directly or indirectly with SE at 16 weeks of age to evaluate the effect of the postbiotic for preventing or reducing SE colonization loads in birds directly or indirectly exposed to the pathogen. Within birds indirectly exposed to the SE inoculation, the postbiotic was associated with a significant reduction of SE-positive individual birds and their associated SE loads when compared to the control birds 7 days after inoculation, with non-significant yet explorable outcomes after 14 days post-challenge. These data support previous research findings in the literature indicating the postbiotic feed additive may aid in reducing SE in poultry production and may therefore be a candidate component of a comprehensive pre-harvest food-safety management plan. Abstract Determining the efficacy of feed-additive technologies utilized as pre-harvest food-safety interventions against Salmonella enterica may be influenced by factors including, but not limited to, mechanism of action, experimental design variables, Salmonella serovar(s), exposure dose, route, or duration in both controlled research and real-world field observations. The purpose of this study was to evaluate the dietary inclusion of a Saccharomyces cerevisiae fermentation-derived postbiotic (SCFP) additive (Diamond V, Original XPC®) on the colonization of cecal and ovarian tissues of commercial pullets directly and indirectly exposed to Salmonella Enteritidis (SE). Four hundred and eighty commercial, day-of-age W-36 chicks were randomly allotted to 60 cages per treatment in two identical BSL-2 isolation rooms (Iowa State University) with four birds per cage and fed control (CON) or treatment (TRT) diets for the duration of study. At 16 weeks, two birds per cage were directly challenged via oral gavage with 1.1 × 109 CFU of a nalidixic-acid-resistant SE strain. The remaining two birds in each cage were thus horizontally exposed to the SE challenge. At 3, 7, and 14 days post-challenge (DPC), 20 cages per group were harvested and sampled for SE prevalence and load. No significant differences were observed between groups for SE prevalence in the ceca or ovary tissues of directly challenged birds. For the indirectly exposed cohort, SE cecal prevalence at 7 DPC was significantly lower for TRT (50.0%) vs. CON (72.5%) (p = 0.037) and, likewise, demonstrated significantly lower mean SE cecal load (1.69 Log10) vs. CON (2.83 Log10) (p = 0.005). At 14 DPC, no significant differences were detected but ~10% fewer birds remained positive in the TRT group vs. CON (p > 0.05). These findings suggest that diets supplemented with SCFP postbiotic may be a useful tool for mitigating SE colonization in horizontally exposed pullets and may support pre-harvest food-safety strategies.