What is one type of concentrate that can be fed to ponies?

Oats are a common type of concentrate that can be fed to ponies. Concentrates are feeds that are high in energy and nutrients and are typically given to enhance the diet of animals, particularly when they require additional energy for work, growth, or other demands. Oats, in particular, provide a good source of carbohydrates and can help with muscle development and energy levels.

In contrast, grass is classified as a forage and serves as a primary source of roughage, providing fiber, but it does not fit into the category of concentrates. Haylage and chaff also belong to the forage category and are mainly sources of roughage; while they can offer important nutrients, they do not provide the concentrated energy that grains like oats do. Therefore, oats stand out as the correct answer for a type of concentrate suitable for ponies.