Historically, starch (specifically corn starch) has been the primary energy source for poultry diets in the United States. As corn is now being increasingly utilized in ethanol production, the cost and availability of starch as a low-cost energy source is being adversely affected. This makes dietary energy the costliest component in poultry diets with little moderation in sight since world consumption of energy will likely continue to increase rapidly. Energy costs will continue to drive grain prices, as more grain is diverted towards bio-fuel production, impelled by high crude oil prices. While continual usage of corn increases dietary costs and reduces margins, reduction of dietary energy might result in either slowed growth rates and/or reduced feed efficiency. Another option, however, is to use supplemental fats and oils to increase dietary energy content. This would allow for continued performance and give the most flexibility to poultry producers when pricing ingredients. Fats and oils have been used by the growing poultry industry around the globe as a supplemental dietary energy source in poultry diets to yield higher levels of metabolizable energy at an economically justifiable price. Hence, understanding fats and their metabolism is a critical factor when it comes to efficient utilization of the dietary energy contributed by fat supplementation.