Animal Science Department


Date of this Version

Spring 5-2014


Hahn, D. 2014. The effects of feed additives, housing systems, and stress on Salmonella shedding in single comb white and brown laying hens. PhD Dissertation. University of Nebraska-Lincoln.


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Animal Science, Under the Supervision of Professor Sheila E. Purdum. Lincoln, Nebraska: May 2014

Copyright (c) 2014 Dana L. Hahn


A series of studies were conducted examining feed additives, housing systems and stress on Salmonella shedding. Alternative feed additives such as prebiotics, probiotics and essential oils have been shown to reduce pathogenic bacteria colonization. Furthermore, stressors such as movement have been shown to increase Salmonella shedding. The goal of the studies was to examine if alternative ingredients reduce Salmonella shedding in alternative housing systems and through movement stress. Study 1 examined cage and cage-free housing with mannan oligosaccharide (MOS) supplementation. Treatments were arranged in a 2x2 factorial design: cage or cage free; MOS (0% or 0.08%). There was no effect on housing system or MOS for Salmonella. E. coli fecal counts increased at 73 wks of age for MOS diets. E. coli and coliforms were three times more likely to be found on eggshells from cage free pens then cage. MOS reduced E. coli colonization in duodenum. Study 2 examined the effect of transportation stress at 16 wks of age on S. enteritidis (SE) shedding through peak lay (33 wks). Incidence of SE positive increased leading up to peak lay. Study 3 examined Salmonella vaccination, movement stress and feed additives in laying hens (43-50 wks of age). Treatments were arranged in a 3x2 factorial design: vaccination (yes or no), feed additive (control, 0.03% MOS or 0.15% synergistic). Feed additives did not have a significant effect on production parameters or Salmonella. Vaccinated hens fed MOS had the highest egg wt. Study 4 examined feed additives on pullets (1 day-22 wks), gut microbiome and SE prevalence (12-22 wks of age). Six treatments were arranged in a completely randomized design: control, 0.01% 1x1010 P. acidilactici , 0.01% 2x1010 live S. cerevisiae boulardii, 0.1% MOS, .01% 1x1010 P. acidilactici+ 0.1% MOS, 0.01% 2x1010 live S. cerevisiae boulardii + 0.1% MOS. Treatments did not have an impact on Salmonella fecal counts, E. coli, coliform fecal and ceca counts or Enterobacteriacea fecal counts. No Salmonella was found in the ceca. All treatments saw a decrease in Enterobacteriacea except for MOS. Current vaccination programs are reducing the risk for Salmonella.

Adviser: Sheila E. Purdum