Oat Hay Hay is vital to the health of small herbivores and needs to be offered to them daily. Oxbow just made it more fun! Oat Hay is a grass hay with a unique taste, look and texture. Its fragrant aroma stimulates your pet's appetite and encourages consumption. Veterinarians recommend hay for the health of your animal. High quality grass hay provides essential fiber, which is absolutely critical for supporting a healthy digestive system. Hay should make up at least 75% of your pet's diet, and should be available for them to eat and forage in at all times.