The huge increase in growth rates of broiler chickens means more than a quarter of these intensively-reared birds have difficulty walking, according to a comprehensive survey. The study identifies a range of management changes that could reduce leg health problems but warns that implementation of these changes would be likely to reduce growth rate and production. The study found that at an average age of 40 days, over 27.6 per cent of birds showed poor locomotion and 3.3 per cent were almost unable to walk. The high prevalence of poor locomotion occurred despite culling policies designed to remove severely lame birds from flocks.