Typically, horses should consume about 2.5% of their body weight daily, but intense training programmes often mean that racehorses often only have limited access to high-quality grass and hay, from well-maintained pastures, and may struggle to consume enough calories to maintain their optimal weight. Consequently, racehorses are typically fed large amounts of cereal-based feedstuffs, such as grain mixtures and oats, to provide the calories they need to perform as elite athletes.
Indeed, oats were once the staple diet of working horses but, because they are low in calcium and macronutrients, such as copper and zinc, and high in phosphorus, are rarely fed in isolation nowadays. Instead, they are fed alongside high-quality hay and grass, vitamin supplements and additional feedstuffs, such as sugar beet pulp, which is a good source of dietary fibre, or roughage, and helps to balance the diet of a typical racehorse. An average racehorse must also drink between five and ten gallons of clean water every day to maintain its health and performance.