It is often said that the horse that wins the race is not the one that can run the fastest but the one that slows down the least.
When it comes to nutritional requirements, racehorses are in a class of their own. They must perform, and this requires a huge amount of energy. Of course, they have a requirement for other nutrients in the diet such as protein, vitamins, minerals and antioxidants, but the primary consideration is energy and how we can safely provide this to minimize digestive upsets.
A significant challenge in feeding racehorses is to achieve and maintain ideal body condition for training and racing while providing enough fuel to support performance at an intense level. For adult and idle horses, the DE requirements are in the region of 60-80 MJ DE for racehorses these requirements are doubled 120-140 MJ DE.
For the horse to move, a chemical reaction must take place that transforms stored chemical energy, into mechanical energy, which is the energy that is required to contract muscles. In the horse stored energy is found in the muscles in the form of glycogen, fatty acids, or to a lesser degree protein. The actual ‘fuel’ needed by the muscles to produce mechanical energy is known as ATP.
There are very low stores of ATP and only enough to fuel exercise for a few seconds but there are numerous pathways that can generate ATP as quickly as it is used, and these pathways use a variety of stored fuels to produce the ATP. To determine the types of diets to feed and the energy substrates to make available we need to appreciate that a racehorse in training and racing will perform both aerobic and anaerobic work and when feeding the racehorse, the aim of feeding is to help optimize the store of these fuels so that the horse can continue to exercise without fatiguing.
The most important fuel for the racehorse is glycogen, which is stored predominantly in the muscle and to a lesser degree in the liver, and fat, which is stored mostly in adipose tissue and to a lesser degree in the muscle.
During a race, muscle glycogen is the major fuel that is used by the racehorse, but fat is also important to supply calories for lower intensity training and to meet the racehorse’s energy requirements for maintenance.
When we look at the energy supply for a racehorse all good rations start with forage no matter how fast or hard a horse is working and unfortunately the importance of forage is often overlooked. It is essential to support optimum digestive health but also to provide a source of energy that is made slowly available throughout the day.
Ideally racehorses should be fed 7-10Kg of high quality and hygienically clean hay, which can be supplemented with smaller quantities of alfalfa hay, 0.5-1.0Kg per day. Meeting the optimum requirement for long stem fibre will help reduce the incidence of gastric ulcers and colic.
Forage alone will not provide the racehorse with enough energy for training and racing and so additional energy must be supplied and this energy deficit is usually made up by using concentrate feeds that are based on using traditional energy sources such as oats, maize and barley. Cereals provide starch and starch is the main energy source of choice for the synthesis of glycogen.
The horse has limited capacity in the small intestine to digest starch and when single large cereal meals are fed there is an increased risk of undigested starch reaching the hindgut where rapid fermentation by the hindgut microbes leads to an increase in acid levels and a change in microbial populations giving rise to conditions such as hindgut acidosis.
Reducing meal size (2.2 Kg) and increasing feeding frequency is key to helping maintain a healthy digestive system.
There are supplements that can be used to help maintain a stable hindgut environment such as hindgut buffers, which are designed to buffer excess acids produced in the hindgut, however, they are not a substitute for correct feed management.
With the advancement in feed manufacturing technology and research it is also possible to replace some of the starch in the ration with alternative energy sources (up to 35%), such as digestible fibre sources e.g. sugar beet pulp and soya hulls. Sugar beet pulp contains a high percentage of readily fermentable fibre and has an energy content that is like that of oats.
Fat is becoming increasingly popular in performance horse rations because it can provide a huge amount of energy in a concentrated form and even though the horses natural diet is very low in fat horses are able to digest fat very efficiently. Once a horse has adapted to a high fat ration they can make use of up to 90% of vegetable oil in a ration. Alternative fat sources such as pelleted rice bran (1Kg per day) is also a very palatable and easy way to significantly increase the energy density of a ration and is particularly useful for fussy feeders or those racehorses that struggle to maintain optimum body condition. Rice bran supplements can be top dressed on top of the normal ration.
There are rations available on the market that already combine these alternative energy sources to ensure a well-balanced ration. Looking at ingredient labels will give you an idea of the variety of different energy sources that are used.
The focus of a racehorse’s ration as mentioned at the beginning should be about how we provide the energy, rather than focusing on how much protein we are feeding. If we are meeting the horse’s energy requirement then usually it will follow that we will be meeting if not exceeding the horse’s protein requirement. The attention given to protein should be that we are providing quality sources (e.g. soya bean meal, alfalfa) that are rich in essential amino acids such as Lysine and Methionine and that we do not excessively exceed the horse’s protein requirement.
Excessive protein should be avoided because it increases water requirement, urea excretion into the digestive tract and blood ammonia levels, which may cause nerve irritability and a disturbance in carbohydrate metabolism. Increased ammonia levels in the stable may also lead to respiratory problems.
By Lizzie Drury MSc Registered Nutritionist.
Saracen Horse Feeds and Eurovets offer a free nutritional and consultation service, if you would like to find out more about racing feeds and alternative energy sources.