Skip to main content
ARS Home » Research » Publications at this Location » Publication #258326
Title: Comparison of shell bacteria from unwashed and washed table eggs harvested from caged laying hens and cage-free floor-housed laying hens

Author
item HANNAH, J - University Of Georgia
item WILSON, J - University Of Georgia
item Cox Jr, Nelson
item Cason Jr, John
item Bourassa, Dianna
item RICHARDSON, L - Former ARS Employee
item Musgrove, Michael
item Rigsby, Luanne
item Buhr, Richard - Jeff

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2011
Publication Date: 7/1/2011
Citation: Hannah, J.F., Wilson, J.L., Cox Jr, N.A., Cason Jr, J.A., Bourassa, D.V., Richardson, L.J., Musgrove, M.T., Rigsby, L.L., Buhr, R.J. 2011. Comparison of shell bacteria from unwashed and washed table eggs harvested from caged laying hens and cage-free floor-housed laying hens. Poultry Science. 90(7):1586-1593.

Interpretive Summary: The eggshells of eggs collected from hens housed in cages had lower levels of APC bacteria than eggs from hens housed on slats or shavings. In addition, washing eggs significantly lowered eggshell bacteria levels and after washing eggs from hens housed in cages, on slats, or on shavings, the level of bacteria recovered did not differ in Experiments 2 and 3 (when the small scale egg processing equipment was used). When all hens were moved to triple-deck cage units in a separate room (2 hens/cage), with manure removal and the absence of shavings, there were subsequently lower levels of aerobic bacteria recovered from both non-washed and washed eggs for both White and Brown hens. After moving hens back to the cages, slats, and shavings room, the level of APC on the eggshells rapidly increased to levels recovered in Experiment 1, although the hen density was two-thirds lower in Experiment 3. However, in Experiment 3, following washing eggs from all three housing systems had much lower levels of aerobic bacteria. For unwashed eggs, APC levels are lowest in housing systems that separate hens from manure and shavings. Spray sanitizing eggs using commercial style egg processing equipment where eggs received varied sanitizing spray patterns lowered APC compared to spraying eggs in place as they rotate. The influence of housing systems in which the eggs were laid was no longer apparent. Following adequate washing of nest clean eggs, the resulting eggshell APC levels are comparable for eggs from White and Brown hens housed in cages, on wire slats, or shavings housing systems.

Technical Abstract: This study evaluated the bacteriology of non-washed and washed eggs from caged and cage-free laying hens housed on all wire slats or all shavings floor systems using Hy-Line W-37 white and Hy-Line brown laying hens. On sampling days for Experiment 1, 2, and 3, twenty eggs were collected from each pen for bacterial analyses. Ten of the eggs collected from each pen were washed for 1 min with a commercial egg washing solution, while the remaining 10 eggs were unwashed prior to sampling the eggshell and shell membranes for aerobic bacteria (APC) and coliforms (Experiment 1 only). In Experiment 1, non-washed eggs produced in a shavings environment had slightly higher aerobic bacteria numbers (APC 4.0 log10cfu/mL of rinsate) than eggs produced on slats (APC 3.6 log10cfu/mL), which in turn had higher bacteria numbers than eggs produced in cages (APC 3.1 log10cfu/mL). Washing eggs significantly reduced APC by 1.6 log10cfu/mL and reduced coliform prevalence by 12%. In Experiment 2, non-washed eggs produced by hens in triple-deck cages from 57 to 62 wk (previously housed on shavings, slats, and cages) did not differ with APC ranging from 0.6 to 0.8 log10cfu/mL. Washing eggs continued to significantly reduce APC to below 0.2 log10cfu/mL. In Experiment 3, the levels of APC for non-washed eggs were within 0.4 log below the APC values attained for non-washed eggs in Experiment 1, although hens in Experiment 3 were at 28% of the hen density used in Experiment 1. Washing eggs further lowered APC levels to 0.4-0.7 log10cfu/mL, a 2.7 log reduction. These results indicate that eggshell bacteria levels are similar following washing for eggs from hens housed in these cage and cage-free environments. However, housing hens in cages with manure removal belts resulted in lower APC for both non-washed and washed eggs (compared to eggs from hens housed in a room with shavings, slats, and cages) and corresponding reductions in human pathogens would further improve food safety.