Dietary fats produce an "extra caloric effect" when fed to poultry. The Appearant Metabolizable Energy (AME) value of feed grade fat, has been shown in energy balance studies to under-estimate the net or effective energy of fat for both laying birds and growing broilers.

It has been suggested that this extra-caloric effect increases the energy content of fat available for maintenance and production with 10% to 20% compared with the efficiency of utilization of AME from carbohydrates.

Dietary fats have also shown to have an "extra metabolic effect" caused by slowing down the passage rate of feed in mature birds, thus increasing the ME of other feed ingredients.