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IPSF: Eggshell Contamination Not Affected by Hen Housing

by 5m Editor
27 January 2009, at 7:08pm

US - Georgia researchers have found that following washing, eggshell bacteria levels are similar for hens housed in cages or in other housing systems, writes ThePoultrySite editor, Jackie Linden.

At the International Poultry Science Forum (IPSF) in Atlanta, Georgia, J.F. Hannah reported work carried out by colleagues at the University of Georgia and the USDA-ARS Russell Center in Athens.

The scientists found that the levels of bacteria on the the shells of eggs from hens housed in battery cages, on slats and on solid floors with shavings were similar, and that washing the eggs reduced the bacterial counts to the same levels for all the housing systems.

All table eggs must be washed in the USA, yet this practice is prohibited in the European Union (with very few exceptions). The regulatory bodies on on both sides of the Atlantic justify their decision as offering better hygiene and reduction of the risk of foodborne diseases.

The Georgia researchers measured aerobic bacteria, Escherichia coli (E. coli) and coliform bacteria on samples of eggs from hens kept in battery cages, on the floor with shavings as litter and on slats. They also looked at two lines of birds: one white and one brown, and sampled the eggs on four different occasions. For each egg sampled, the shell was crushed in sterile medium and the bacterial counts were carried out on the resulting rinsate.

Half of the eggs from each treatment were washed for one minute with a commercial egg washing solution.

Unwashed eggs from the birds housed on shavings had slightly higher bacterial numbers (APC 4.4 and coliforms 1.1 log10cfu per mL) than eggs produced on slats (APC 3.9 and coliforms 1.1 log10cfu/mL). These two treatments had significantly higher bacterial numbers than the eggs produced by caged hens (APC 3.2 and coliforms 0.7 log10cfu/mL).

Washing the eggs from hens in cages, on shavings and on slats significantly reduced APC counts by 1.1, 1.7 and 1.7 log10cfu/mL) of rinsate, respectively.

E. coli and coliform counts were not affected by housing type, and were not significantly reduced by washing.

Laying hen strain had no effect on egg shell bacteria recovery levels.

No significant differences were found in APC, E. coli or coliform counts on eggs obtained from the three housing types following washing.

Ms Hannah said that it would be valuable to repeat the experiment, looking at other bacteria causing food borne disease, such as Salmonella.