Cereals are commonly used in pig diets as the main sources of energy. However, depending on price and availability, diets of equivalent energy content can be formulated using combinations of oil and cereal by-products. The use of oil as an energy source has been shown to improve average daily gain (ADG) feed efficiency and increase digestible energy intake (DEI) (Overland et al 1999). However, there is a need to examine the response in pig performance to incremental levels of oil inclusion compared with the performance of pigs offered cereal-based diets. Therefore, the aim this study was to examine the effects of offering cereal-based diets or diets containing by-products and oil on the growth performance of commercially housed growing pigs.