Effect of a Yeast Cell Wall Preparation on Cecal and Ovarian Colonization With Salmonella enteritidis in Commercial Layers

Salmonella enteritidis (S.E.) was the most common serotype in human infections in 2016. Various yeast products have been shown to inhibit colonization of chickens by Salmonella and could be a useful adjunct in an S.E. control strategy. This study sought to determine whether feeding a yeast cell wall product (Celmanax SCP) at 100 ppm to commercial layer pullets either from 1 d to 17 wk or from 10 to 17 wk would affect S.E. colonization of both the digestive tract and ovaries. At 16 wk of age, the pullets were orally challenged with 1.8 × 109 CFU S.E. and then ceca and ovaries were assayed at 1 wk post challenge for S.E. prevalence and load. The colonization level was very high in the ceca with many counts too numerous to count (>106 most probable number (MPN)/g, TNTC). A censored regression model was used to account for the large number of TNTC samples from each treatment group. Both of the Celmanax SCP-treated groups had an estimated marginal mean log10 MPN that was numerically lower than that of the untreated challenged positive control group by about 1.5 log10, and while this difference approached significance, it was not significant at the 5% level (P = 0.056). Although the proportion of isolates that exceeded the upper limit of the MPN assay was numerically lower for the group fed Celmanax SCP from day 1 (25.5%) than for the group fed Celmanax SCP from 10 wk (43.8%), or the untreated challenged positive control (47.9%), this difference again approached but did not achieve significance at the 5% level (P = 0.060). Also, there was no significant difference between challenged treatment groups with respect to ovary Salmonella prevalences (P = 0.322).