Prof Julian Wiseman’s letter (14 April) makes important distinctions on the diet of poultry, but misses our point. My claim was never that chickens cannot physically eat other things, but that the factory-farming business model cannot function without cheap imported soya. Modern, fast-growing broilers – the Ross 308 or Cobb 500 being the dominant commercial examples – were selectively bred over decades in an environment of cheap, abundant soya protein, and their genetics and feed system are now coadapted. Their rapid growth relies on the dense protein that soya bean meal provides. Soya underpins modern global poultry production. Reliance on it carries mounting environmental and economic risk, with soya linked to illegal deforestation.

Wiseman is correct that soya is the most complete plant protein. That is precisely the problem. UK soya bean production is negligible: soya doesn’t grow well here. To produce meat at scale, the UK imports more than 3m tonnes of soya annually – 68% comes from South America, with over 1m tonnes used for broiler chickens alone. These birds are also more prone to digestive stress from their unforgiving, rapid rate of growth. Mounting evidence shows slower-growing breeds, raised in less intensive systems, can thrive on a wider range of feeds and offer a more resilient and humane alternative.

So while Wiseman is correct on the narrow frame of animal nutrition, our argument is about the wider system. Cheap chicken relies on high volumes, tight margins and imported soya. That model looks increasingly fragile. There are many possible solutions for our collective food future, but factory-farmed chicken is not among them.
Ruth Tanner
UK country director, World Animal Protection