Feeding Young Racehorses

When young Thoroughbreds are put into race training late in their yearling year or early in their two-year-old year, their lifestyle goes through some significant changes. Instead of being turned out in small herds with their pasture buddies, they are individually stalled. An hour or so of ridden exercise replaces hours of free-choice outdoor exercise. Feeding changes include a shift from grass to hay and, in most cases, an increase in the volume and frequency of grain meals. For equines that will continue to grow and mature for at least two more years, these management modifications have the potential to cause problems with the digestive and skeletal systems if the diet is not carefully planned.

As the horse continues to grow and mature, it is expected that he will gain weight as his skeleton and muscles increase in size. Regular weighing is a good idea, but trainers should also evaluate body condition by checking visual appearance and doing a hands-on examination to see that there is adequate fat covering the withers, ribs, spine, and hindquarters. As the horse gains fitness he will appear more muscular, but he should not drop below a score of about 4.5 to 5 on the Henneke scale of body condition.

The horse’s feeding program must provide plenty of energy for growth, training, and maintenance of body functions. It must also be balanced as to calcium and phosphorus to support skeletal maturation. Finally, protein levels need to be adequate to ensure development of muscles, blood, and connective tissue.

Supplemental energy needed to fuel exercise is traditionally derived from grain meals. Because the ingestion of high levels of grain has been linked to insulin spikes, gastric ulcers, and hindgut acidosis, many trainers have moved from straight cereal grain (oats, corn, barley) meals to fortified feed products that include fat and fermentable fibers (beet pulp, soy hulls) as energy sources. These feed ingredients do not entirely replace grain in most cases, but they have benefits such as quieter behavior and fewer digestive upsets for many young horses in training. Adding fat means that a smaller meal will supply the same calories as a larger grain meal because fat contains more than twice the energy as the same volume of starch. Also, the metabolism of fat involves less heat production than when starch is metabolized, so horses do not need to get rid of as much body heat as they exercise.

Mineral balance is important, especially for calcium and phosphorus, as horses enter training. The horse’s free exercise is limited by stalling; he is asked to carry the weight of a rider for the first time; and his bones lose density from the decreased exercise before they begin to remodel in response to training. Calcium and phosphorus are both needed for bone development, but these nutrients must be supplied in the proper ratio to avoid problems. The horse’s complete diet—both grain and hay–should be considered in this balance. Most commercial horse feed products offer the correct mineral ratios, but hay varies in calcium content so it is important to evaluate this component to be sure the horse is getting what it needs to build strong bones. For example, alfalfa (lucerne) hay is much higher in calcium content than grass hay. Trainers should have hay analyzed to get an idea of its mineral balance, and they can check with an equine nutritionist to see if the diet is correctly designed for young horses in race training.

Protein is necessary for maintenance of body tissues, but it is especially important in young horses that are increasing their muscle mass. As well as containing varying amounts of calcium, hay also varies in its protein content, with alfalfa hay containing a higher level than grass hay. Commercial feeds formulated for young horses in training usually contain adequate protein for these animals, so if large amounts of alfalfa are fed, the horse may be getting more protein than what he needs. Excess protein is excreted in the urine, causing a strong ammonia smell that can irritate the horse’s respiratory tract. To design a feeding plan to find the right level of dietary protein, check feed labels, be aware of protein content of hay, and ask an equine nutritionist for guidance.