Whey, which is a co-product from dairy processing plants that extract fat and protein from milk to make cheese, has been used in diets fed to weanling pigs as a source of lactose. Whey powder does not contain much protein because the majority of the milk protein ends up in the cheese during processing. However, cheese co-products, which contain 40 to 50% crude protein may be used in the feeding of pigs, but there is limited information about the nutritional value of cheese co-products fed to pigs. Therefore, the objective of this research was to test the hypothesis that a cheese co-product may replace traditional protein sources in diets for weanling pigs without affecting growth performance.