High quality hay makes up most of a racehorse’s diet, but since their energy requirements are so high, starch, fat and protein are added to meet those energy needs.
Photo by Anne M. Eberhardt
No matter which equine nutritionist or Thoroughbred trainer you speak with about feeding a racing Thoroughbred, you will get the same response: You want to obtain the highest level of performance with minimal digestive disturbances. Therefore, you must feed each horse as an individual.
Thoroughbred racehorses exist in a class of their own when it comes to their nutritional requirements. Racehorses must physically perform at a high level of intensity, and that means they need lots of dietary energy. Amy Parker, MS, equine nutritionist at McCauley’s Feeds, in Versailles, Kentucky, says racehorses are considered equine athletes that must be fed enough energy to maintain their body weight and body condition and meet their energy requirements for racing. This energy must be provided in a reasonable amount of daily feed that the horse can safely consume.
How Much Energy Thoroughbred Racehorses Need
Thoroughbred races typically range in distance from 4 furlongs (½ mile) to 12 furlongs (1 ½ miles), and they can have run times as short as one minute up to more than two minutes. The duration and speed the horse runs makes a difference in the major fuel he utilizes.
During regular training and racing, the horse must perform both aerobic and anaerobic work. Aerobic work occurs with exercise at a lower heart rate (usually not more than 150 beats per minute [bpm]). A horse performing aerobic work can get enough oxygen to the tissues to burn fat as his fuel source. During anaerobic work (heart rates above 200 bpm), the horse relies on the fuel source that can operate in the absence of oxygen: blood glucose and glycogen (a complex string of glucose molecules).
Racehorses must have a full complement of fuel within their muscles ready to be utilized when they run a race. At that time they use one fuel source stored predominantly in the form of glycogen. Breaking down muscle glycogen is essential for the muscles to rapidly produce adenosine triphosphate (ATP), which is a small molecule necessary for muscle contractions. They store fat primarily in adipose tissue and utilize it during lower-intensity training. It also helps meet the horse’s maintenance energy requirement.
The objective of feeding a racing Thoroughbred is to optimize all his fuel stores so the muscles can work (contract) efficiently without him becoming fatigued due to lack of adequate fuel. As the Lexington, Kentucky-based Thoroughbred trainer Destin G. Heath says, “It’s not only our job to make sure they get what they like but that it meets their nutritional needs.”
The Digestible Energy Thoroughbreds Need
Dietary energy (DE) refers to the amount of energy in the diet absorbed by the horse and is usually expressed in megacalories (Mcal). One Mcal is equivalent to 1,000,000 calories, or 1,000 kilocalories. Nutritionists calculate DE requirements based on what the horse needs for daily maintenance plus any additional exercise. To put that into perspective, the DE for maintenance for an idle adult horse weighing approximately 1,000 pounds is about 16 Mcal per day. Double that for a racehorse’s DE requirement.
Trainers provide the energy racehorses need in the form of fiber, starch, fat and protein.
Parker says fiber is probably the most important energy source for the racehorse. Horses have a highly developed hindgut that contains billions of bacteria and protozoa capable of fermenting fiber. The product of fiber fermentation provides the horse energy he can utilize throughout the day.
Because proper gastrointestinal function is imperative to the overall health of the horse, a forage rich in fiber should be the foundation of the racehorse’s dietary program. Heath explains that providing racehorses with high-quality free-choice grass and leafy alfalfa hay not only provides the horses with the necessary calories but also satisfies their need to chew. It helps horses stay occupied, especially if they stand in a stall for extended periods of time. Parker adds that alfalfa hay contains high calcium and magnesium concentrations, which have antacid-like effects and can help reduce the incidence of gastric ulcers.
Due to the amount needed to meet a racehorse’s DE requirements, feeding fiber alone does not provide enough energy for him to adequately perform. Therefore, the additional DE must come from other sources.
Concentrate Feed for Thoroughbred Racehorses
Starch is a dietary energy source. Traditionally, trainers supplied starch with cereal grains such as oats, corn or barley. Digesting starches raises blood glucose and insulin, which are both involved in glycogen synthesis. However, a racehorse’s ration should contain a limited amount of starch. Avoiding large grain meals helps the small intestine fully digest the starch of cereal grains. The hindgut, which is also referred to the large intestine, rapidly ferments any starch that spills into the cecum and colon, decreasing hindgut pH and resulting in hindgut acidosis. This condition can lead to horse health issues including colic, laminitis, reduced performance and hindgut ulcers.
Heath says that by feeding multiple meals of a balanced feed per day, he can provide horses with their required daily calories, thus mitigating the risk of starch spilling into the hindgut. “Because some of my horses are eating 24-32 quarts of feed per day in order to have enough energy to perform, I may feed five meals per day.”
Feeding Fat to Thoroughbred Racehorses
Trainers also use fat as an energy source in racehorse diets. While these equine athletes might consume high-grain diets to meet their energy demands, the high levels of sugar and starch can increase the risk for gastric ulcers, says Parker. She suggests increasing fat content in the diet to reduce sugars and starches without compromising the calorie concentration. Once horses adapt to fats, they digest them quite efficiently.
Fats provide a concentrated supply of energy in an amount of feed the horse can consume safely. “You can use a feed that contains an elevated fat concentration or top-dress the current feed with a high-fat supplement, such as vegetable oil, ground flaxseed or rice bran,” says Parker. Fat can be incorporated up to about 10% of the concentrate without negatively impacting fiber digestibility.
“We have shifted away from feeding racehorses straight cereal grains because there are a lot of commercial feeds out there that are specifically formulated for the racehorse,” says Heath. Manufacturers of these feeds use alternative energy sources such as fat and fermentable fiber to reduce the energy supplied by starch (cereal grains).
Other Key Nutrients for Thoroughbred Racehorses
Parker emphasizes that providing good-quality protein is essential for building muscle in racehorses. Essential amino acid concentration determines protein quality. Good-quality protein sources for horses include soybean meal and alfalfa. A racehorse needs slightly more protein than horses on maintenance. If the horse consumes excess protein, he can only use some of the extra as an energy source. He excretes the rest as ammonia, which increases urine volume and water needs, causing metabolic stress. Extra protein is also an unnecessary expense. So, protein generally should not be the most critical consideration when feeding racehorses.
Racehorses can lose up to eight gallons of water through sweat in a race, says Parker. The horse needs to rehydrate and also loses electrolytes such as sodium, chloride, potassium and magnesium in sweat. Replenishing electrolytes helps the thirst response, muscle contraction during and muscle recovery following exercise. Heath recommends the proven practice of providing water immediately following the race and allowing the horse free access to salt. Giving orally drenched electrolytes might be useful if the horse races under hot and humid conditions. The most effective way to meet a horse’s electrolyte needs is by providing a balanced diet of high-quality hay and concentrate that contain all required minerals, ensuring they are fed in amounts that meet the horse’s energy requirements.
Take-Home Message
Heath says it is critical to provide each horse with enough calories, so he has enough energy to do his job and stay in good body condition. “It’s our job to adjust and assist each horse. They can’t pick (the feed) we give them, so we must feed them the best feed based on each individual.”
