The success of the poultry industry since the end of the Second World War has been based very considerably upon the introduction of increasingly productive strains of birds. This has been achieved by intensive selection for productive characteristics such as growth rate, meat yield and egg productivity. However this emphasis on production attributes seems to have resulted in birds that have pronounced weaknesses in other characteristics that become manifest in a range of metabolic disorders. The severity and impact of these disorders is such that there needs to be a re-evaluation of the basis for continued genetic development of poultry stock.

The main metabolic disorders affecting modern poultry are those involving skeletal and cardiac systems. There are three main types of skeletal disorder: bone growth abnormality in meat poultry, bone fragility in laying hens and cartilage disorders in heavy breeding birds. The main cardiac disorders are ascites and sudden death syndrome.