the use of antibiotics in swine production has been changing to more restricted use of in-feed antibiotics because of potential safety issues of use of antibiotics for livestock animals. In addition, the cost of conventional feed ingredients such as corn or soybean meal has markedly increased, resulting in increased use of cheaper co-products to replace partially them in swine diets. Due to the above two main issues, swine production industry has increasingly considered the use of all kinds of alternatives not only to reduce feed cost but also to improve pig performance and health.