The concerning rise in 'hock burn' among British supermarket chickens

Millions of UK chickens are suffering skin damage from being forced to live packed together in their own waste, a new investigation has found. 

"Hock burn", caused by ammonia in excrement, is visible on a third of supermarket birds, according to data analysed by the BBC. It is associated with a "high stocking density of birds", a result of "prolonged contact to moist, dirty litter", and shows up on prepared meat as brown ulcers on the back of the leg. 

Although hock-burnt chicken is safe to eat, the amount of burn in a flock is an "industry-accepted indicator of wider welfare standards on farms", said BBC News's rural affairs producer Malcolm Prior. The issue is taken "very seriously", said the British Retail Consortium. 

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'Consequences of poor litter quality'

The UK's biggest farm and food assurance scheme, Red Tractor, sets a target of no more than 15% hock burn in their flocks. Health and welfare of meat chickens (known as broilers) is directly linked to litter quality, according to the government, and "conditions such as hock burn…are usually consequences of poor litter quality". 

Current legislation requires that all chickens have permanent access to dry litter, said a Defra spokesperson. 

But the "concerning" condition is "sadly, too common in many intensive farm settings", RSPCA poultry specialist Kate Parkes told the BBC.

The risk is "significantly higher when birds are poorly managed, genetically selected to grow very fast or reared in overcrowded conditions", she added. 

The broadcaster asked the UK's 10 biggest supermarket chains, including Tesco, Sainsbury's, Waitrose, Aldi and Co-op, about the annual rates of hock burn in chickens they stock. 

Co-op had the highest rate, with 36.7% of its poultry found to have hock marks, while Aldi reported 33.5%. "Every effort" was made to minimise the occurrence of hock burn, said a Co-op spokesperson, while an Aldi spokesperson added that it worked closely with suppliers to "ensure continuous improvement in our food".

Waitrose had the lowest hock-burn rate, at 2.7%. It told the BBC it had reduced hock marking levels by 80% between 2014 and 2022 by monitoring environmental conditions on farms and training farmers. "It's our ambition to make hock burn a thing of the past," a spokesperson said.

'Bred for extremely rapid growth'

Five chains – Asda, Morrisons, Iceland, Ocado and Lidl – refused to release their data.

But one animal welfare campaign group, Open Cages, has been focusing on Lidl for "store spot checks", said Science Times. Volunteers examined more than 500 whole chickens in 22 UK branches between September and November last year. They found that 74% showed signs of hock burn. 

This burn is just "one symptom of a much larger problem", according to the group's co-founder, Connor Jackson. Many retailers source chicken farmers "keep chickens in overcrowded sheds and breed them for extreme and fast growth. This routinely leads to suffering for chickens".

The group's report claimed that members detected "white striping disease" in 94% of Lidl's packaged chicken breasts – a muscle disorder "characterised by white lines across the breast meat, linked to poultry growing to large sizes rapidly", said National World. Breast meat affected by white striping can be higher in fat, according to Open Cages.

Lidl said that Open Cages' findings did not match their own figures, and that the health of animals in its supply chain was "closely monitored, with regular independent audits carried out".

The British Poultry Council told the BBC that "drawing comparison between formal inspection and rigorous procedure versus a shop-shelf experiment has potential to mislead and misinform".

But Open Cages is calling on Lidl, and other British retailers, to sign up to the Better Chicken Commitment (BCC) – a set of international welfare standards for broiler hens.

Although it is only the UK's seventh biggest supermarket franchise, Lidl is (via the Schwarz group) the largest retailer in Europe. Jackson told National World that Lidl's support could help drive other chains to adopt the BCC. 

"They have a uniquely powerful influence on the future of animal welfare," he said. "If Lidl moves on this, then everyone moves. So we feel that with great power comes great responsibility."