Know more

Our use of cookies

Cookies are a set of data stored on a user’s device when the user browses a web site. The data is in a file containing an ID number, the name of the server which deposited it and, in some cases, an expiry date. We use cookies to record information about your visit, language of preference, and other parameters on the site in order to optimise your next visit and make the site even more useful to you.

To improve your experience, we use cookies to store certain browsing information and provide secure navigation, and to collect statistics with a view to improve the site’s features. For a complete list of the cookies we use, download “Ghostery”, a free plug-in for browsers which can detect, and, in some cases, block cookies.

Ghostery is available here for free:

You can also visit the CNIL web site for instructions on how to configure your browser to manage cookie storage on your device.

In the case of third-party advertising cookies, you can also visit the following site:, offered by digital advertising professionals within the European Digital Advertising Alliance (EDAA). From the site, you can deny or accept the cookies used by advertising professionals who are members.

It is also possible to block certain third-party cookies directly via publishers:

Cookie type

Means of blocking

Analytical and performance cookies

Google Analytics

Targeted advertising cookies


The following types of cookies may be used on our websites:

Mandatory cookies

Functional cookies

Social media and advertising cookies

These cookies are needed to ensure the proper functioning of the site and cannot be disabled. They help ensure a secure connection and the basic availability of our website.

These cookies allow us to analyse site use in order to measure and optimise performance. They allow us to store your sign-in information and display the different components of our website in a more coherent way.

These cookies are used by advertising agencies such as Google and by social media sites such as LinkedIn and Facebook. Among other things, they allow pages to be shared on social media, the posting of comments, and the publication (on our site or elsewhere) of ads that reflect your centres of interest.

Our EZPublish content management system (CMS) uses CAS and PHP session cookies and the New Relic cookie for monitoring purposes (IP, response times).

These cookies are deleted at the end of the browsing session (when you log off or close your browser window)

Our EZPublish content management system (CMS) uses the XiTi cookie to measure traffic. Our service provider is AT Internet. This company stores data (IPs, date and time of access, length of the visit and pages viewed) for six months.

Our EZPublish content management system (CMS) does not use this type of cookie.

For more information about the cookies we use, contact INRA’s Data Protection Officer by email at or by post at:

24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

Menu Logo Principal

Home page

Laying hen breeding systems and hygienic status of the eggs

Laying hen breeding systems and hygienic status of the eggs


1 INRA, Unité Recherches Avicoles, F-37380 Nouzilly, France

2 AFSSA, Laboratoire d’Etudes et de Recherches Avicoles, Porcines et Piscicoles, BP 53, F-22440 Ploufragan, France

3 Institute for Agricultural and Fisheries Research, Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgique


Due to the expected ban in 2012 of conventional cages for laying hens, new breeding systems are being developed. The impact of these systems on the hygienic status of the eggs was studied.

The contamination of the egg shell by bacteria is significantly higher in free-range systems compared to furnished or conventional cages. These differences are lower in commercial conditions than in experimental studies. This could be explained by differences in breeding practices in the different breeding sites compared. The differences observed between furnished and conventional cages are lower and not constant. The percentage of eggs laid in the nest but also the disposition of the furniture (nest, perch and scratching area) may significantly affect the bacterial load of the egg shell. Many other factors such as cracks or dirt on the shell, dust concentration in the rooms or season may also influence bacterial egg shell contamination.

Studies also show that it is highly unlikely that a move from conventional cages to alternative cage systems and non-cage housing systems for laying hens will result in an increase in Salmonella infection and shedding, rather the opposite is expected.

Download documents