Oats are the highest in fibre and contain the least amount of energy when compared to other cereals such as barley and maize and because of this are not as likely to make horses and ponies fizzy or hyper. Oats are best fed to horses in hard work, such as racehorses and competition horses, but they can be fed in small quantities to an existing horses feed to give it a bit more 'oomph' Oats should not be fed on their own as they are low in calcium and phosphorus.