Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2003
Publication Date: 1/20/2004
Citation: Jones, D.R., Curtis, P.A., Anderson, K.E., Jone, F.T. 2004. Microbial contamination in inoculated shell eggs: II. effects of layer strain and egg storage. Poultry Science. 83:95-100. Interpretive Summary: The comparison of historic strains of laying hens to a current flock allows for a greater understanding of changes due to genetics. In the current study, the microbial integrity of egg produced from three historic random-bred control strains and a current commercial laying flock was examined. Eggs were inoculated with Salmonella Enteritidis and Pseudomonas fluorescens (spoilage organism). Eggs from the control strain developed in 1972 were better able to withstand the microbial challenge during storage than eggs from flocks developed in the 1950s, 1960s, and 1990s. Genetic selection appears to have some effect on the antimicrobial properties of shell eggs even though it is not generally a point of consideration during the process. The results from this study indicate that the microbiological integrity of the egg should also be considered during genetic selection.
Technical Abstract: Three Ottawa control strains and a current commercial laying stock were reared and housed in the same environment. Eggs were collected at five different hen ages throughout the two production cycles of the flock. The eggs were inoculated with Salmonella Enteritidis (SE), Pseudomonas fluorescens (PF), a combination of the two, or sterile buffered peptone water and stored for up to 5 wks. After storage at room temperature, contamination levels were determined for the exterior surface, air cell, egg contents, and within the shell. Interior, egg contents, and shell contamination levels of both SE and PF increased with storage time. There were no apparent increases in the infectivity of SE or PF in the presence of the other organism. PF was a poor survivor on the shell surface under these storage conditions. Throughout the five week storage, the Control Strain 10 eggs maintained their microbial integrity more effectively. Eggs from Control Strain 5 and the current commercial stock were more easily contaminated than the other strains. These data suggest that genetic selection has altered microbiological defenses of the eggs produced.