Feeds with high amount of fibre are classified as "roughages". Roughages are feeds that contain a high proportion of fiber relative to other nutrients. These include forages such as grasses, hay, and silage, as well as other fibrous feeds such as straw and corn stalks. Roughages are important in the diets of many livestock species because they provide bulk in the diet, which helps to stimulate digestion and keep the digestive tract healthy. They also tend to be less expensive than concentrates, which are feeds that are high in energy and low in fiber.