Sampling Procedures for Free Range Laying Flocks

Published on : 5 Sep 2022

It is now over 10 years since the implementation of the EU Regulation 2160/2003, under which eggs from flocks infected with salmonellae of human health significance (or from flocks not tested in accordance with the national control programme,(NCP)) are not allowed to be sold for direct human consumption. The salmonellas of human health significance are non-vaccinal strains of Salmonella Enteritidis and Salmonella Typhimurium.  As I write this it remains uncertain if, how, and when Brexit will occur, but the government has stated that a series of protections under EU law will not be reduced after Brexit.  This seems very likely to be one of them.

Operator sampling under the NCP has limited sensitivity but is capable of detecting Salmonella infection when carried out correctly.  It is supplemented by annual official sampling of one flock per farm by NSF auditors (for Lion Scheme farms) or APHA egg inspectors for others, which is more sensitive because an extra sample is taken. BEIC has requested that verification sampling of all houses be carried out in the next 12 months or so. Should either operator or official samples prove positive, Defra no longer carry out routine confirmatory sampling (in fact they have never done this for official samples).   Producers may, however, opt for confirmatory testing of either “enhanced environmental samples” (5 pairs of boot swabs tested individually, and 2 sets of dust samples), 300 carcases, or 4,000 eggs. However, the eggs produced until a negative result is obtained are downgraded to Class B. If the producer does not opt for this testing, or it is found to be positive, all other flocks on site are subject to official enhanced environmental sampling.

Egg producers are the key link in a food production chain (which includes the layer breeders, hatcheries, pullet rearers, feed producers, egg packers, and testing laboratories. If we fail to detect an infected flock through inadequate sampling, it is possible that the immunity conferred by vaccination will be overcome and that consumers could be harmed.  There have been a small number of cases of infected laying flocks since the NCP began, and the ability of ‘Whole Genome Sequencing (WGS)” to link widely separated individual human cases has shown its value in identifying different sources of Salmonella infection.

If, in the past, a producer regarded his operator sampling as a chore which could be delegated, and was not very important, then he or she should think again!  It is not in the interest of the producer, particularly those with multiple flocks on site, not to identify the first infected flock early.  Failure to do so may allow the infection to spread to other flocks on the holding, or result in early infection in the next flock in a house, or even onward spread to other farms.

Detailed advice on the collection of operator samples is available from poultry veterinary practices, testing laboratories and fieldsmen/women for egg packers. It is also covered by training modules under the ‘Lion Passport’ training scheme.