Thinning of broiler flocks is no longer permitted in the United Kingdom under the welfare standards for chickens set up by the farm assurance scheme set up by the Royal Society for the Prevention of Cruelty to Animals (RSPCA). First published in 2013, the standards include a requirement to end the practice by January 1, 2016.

“Thinning - rearing chickens within a shed to the maximum stocking density permitted, removing a proportion of them, and then rearing those remaining to higher weights, which can take place several times before all the birds are finally removed - can be a stressful experience for the birds,” said Dr. Marc Cooper, chicken welfare specialist at the RSPCA. “For example, their feed is removed to allow catching teams to collect the birds more easily, and the temperature inside the shed can drop, particularly during the winter, as the teams enter.”

The reason for this change is the challenge to reduce the levels of foodborne disease in humans caused by Campylobacter. Incidence has remained stubbornly high, and around three-quarters of cases of food poisoning cases caused by this bacterium have been linked to the handling or consumption of poultry meat. Under European Union regulations, only water (without chemicals added) may be used to treat broiler carcasses in the processing plant – a process that is ineffective in removing Campylobacter.

In 2010, the European Food Safety Authority (EFSA) published a report which stated that “a higher Campylobacter count on carcasses was strongly associated with Campylobacter colonization of the batch” and that chicken “batches originating from previously thinned flocks were more at risk of being colonised with Campylobacter.”

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The Food Standards Authority (FSA) set up the Acting on Campylobacter Together campaign with many stakeholders in 2009 to bring together the whole food chain to reduce levels of Campylobacter in chicken and to reduce the burden of foodborne illness.

Campylobacter control measures in U.S.

In December of 2015, the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA FSIS) published revised guidelines to assist poultry processors in controlling Salmonella and Campylobacter in raw food products, including poultry products, and prevent cases of foodborne illness. This updated document – “FSIS Compliance Guideline for Controlling Salmonella and Campylobacter in Raw Poultry” - is intended to offer poultry companies best practices for minimizing pathogen levels and meeting FSIS’ food safety requirements.