It is tempting to think of a racehorse as a completely different creature to the leisure horse that has hairy heels and isn’t very fast. However, their insides aren’t that different! The racehorse will probably have a larger heart and a higher muscle to body fat ratio, but if you took a look at their digestive tracts, you might be surprised to see that they are more or less the same.
The racehorse and leisure horse have requirements for exactly the same nutrients, albeit in different amounts, and their requirement for fibre and their need to chew and to trickle-feed are exactly the same. Unfortunately it became common practice to feed racehorses for their energy and protein requirements without any concern for their fibre requirements, need to chew and need to have a partially filled stomach at all times. Doing so does not foster good heath nor lead to optimal performance, may cause stomach ulcers and contributes to early breakdown. Nowadays, racehorse diets tend to be better, with higher fibre feeds used and more forage fed, but there is still room for improvement in many yards.
Racehorses and other sports horses work hard and as a result most of their nutrient requirements are increased compared to leisure horses in light to moderate work. The primary difference in their diets to leisure horses is the amount of energy they need. Energy is obtained from dietary carbohydrates (including fibre) and oil, but not to any great extent from protein (so a 14% protein feed tells you nothing about its suitability for racehorses). Hard working horses also have slightly higher protein requirements, and the quality of their protein needs to be higher too. They also have higher vitamin and mineral requirements, much higher sodium (salt) requirements and will drink more water too.
Just as for every other horse (with the exception of specific clinical cases), racehorses should have as much of their nutrient requirements as possible fulfilled from forage, with other feeds and supplements chosen based on what the forage is lacking. It is an error to choose a racehorse feed (be it oats, racehorse cubes or racing mix), feed a set amount e.g. 6 kg per day, and then throw in forage of unknown nutrient content. In fact, traditionally, racehorses were fed relatively stalky, fibrous hay because the high starch and low fibre content of their diet (e.g. oats alone) would cause digestive issues if adequate fibre wasn’t added. Feeding in this way doesn’t make any sense. A high quality forage that supplies good levels of energy and protein should be chosen, so that healthy levels of concentrate feed can be given, which will not cause digestive upset. No horse should ever be fed less than 1% of its bodyweight per day (about 5 kg for a typical 500 kg horse) in fibrous forage (or forage alternative). Such an amount of forage will not slow a sprint racehorse down. Oats, the traditional racehorse feed, are the best choice of straight cereal for horses, but they must be balanced (especially for protein and minerals) if nutrient deficiencies are to be avoided. Compound feeds containing highly digestible fibre and high levels of oil are useful because they can be fed in relatively large amounts without risking digestive upset.
For racehorses and elite sports horses, the quality of the feed is important because peak performance is required. Factors that matter include: absence of mycotoxins, keeping feed bowls, mixing utensils and feed bins clean, choosing hay free from dust and ideally steaming it (or choosing haylage), and never feeding out of date compound feed. Of course, these factors matter for optimal health in leisure horses too!
The basis of feeding racehorses and leisure horses is the same, and for optimal health and performance, racehorses need plenty of fibre, controlled dietary starch and should never be allowed to fast for over 4 hours.