There is no single diet that will suit all horses. The best diet for a your hourse depends on the type of horse you own, what you use it for, and the type of pasture, if any, that it is kept on. For instance, a horse used for an occasional weekend canter will need a lot less energy than a race horse in full training.
The most important component of a horse's diet is roughage and the most important roughage is grass. At least half of a horse's daily intake of food should be roughage of some form and this can include hay. Your horse should be allowed to graze freely as much as possible. Grass is not only good for it, but by wandering casually around the pasture in search of succulent grasses, your horse is helping to alleviate boredom. However, if you have a lush green pasture and your horse is very hungry, it is wise to feed the horse hay first before you release it. Failing to do so could allow the horse to gorge on the lush grass and a potentially serious condition called colic can result.
Hay is an important form of roughage and lucerne (alfalfa) hay is the commonest that is used. Good quality hay should be free from dirt and should show no sign of dust or mould. It should be dry when parted and should not be hot as this indicates that it is composting. The hay should appear clean and weed free.
Some say that you can judge the quality of a hay by how enjoyable the loose hay would be to sleep on!
During cold weather, such as we have at present, a horse requires more roughage because when roughage is digested in a horse's caecum (part of its intestine) it releases a great deal of heat - just like an internal hot water bottle! In cooler weather, a horse will really burn up hay to keep itself warm.
Lucerne hay is also a mild laxative. It contains good quality protein and is high in several important vitamins. A horse fed solely on good quality hay will eat about two and a half percent of its body weight daily. For a 400kg horse, this will amount to 10kg of hay per day.
You can also feed your horse on lucerne chaff. The main advantage of chaff is that it can be easily mixed with concentrates such as grain or pellets. However, lucerne chaff is quite light and it is easy to underestimate the roughage you are giving, especially if you feed by volume rather than weight.
There are limitations to an all-roughage diet. The most important is that it is low in energy and may not give enough calories for a horse that is working. Hay can distend the underline, giving the horse a 'hay-belly' or 'pot-belly'. Hay-belly can be reduced by mixing a pelleted complete food or a concentrate with the roughage.
Horses are often fed grain. Grain is a concentrated form of food and some caution is needed. If too much grain is fed, a condition called laminitis or founder can result. Laminitis is a condition of the hoof in which the tissues supporting the bones inside the hoof deteriorate. This allows the bone inside the hoof to rotate or move into the wrong position. It is very painful and can disable the horse permanently. Adding chaff to grain will slow the intake of the concentrate and reduce the chance of laminitis.
Grain should not make up more than 50 percent of the daily ration fed to a horse and it is better to feed the horse a small amount of hay before the grain is given. Most grains are processed by cracking or steam-rolling. This opens the seed so that it can be digested more easily.
However, oats are an exception to this rule. Oats are by far the most common grain fed to horses because of it is relatively safe, not costly, and the fact that there is no need for further processing.
Lastly, if your horse is in poor condition, look in its mouth. Teeth that have developed sharp edges or that have grown to uneven lengths will prevent the horse from grinding the food properly. In turn, this will lead to a drop in body condition. Poor condition of the teeth is suggested if the horse is lean despite being fed good quality food, and if its manure shows undigested grains. Many horses with bad teeth will also drop food from their mouths and will slobber as they are eating.
To correct this problem, the teeth can be filed by a veterinarian.
Horse nutrition is a complicated topic. If you have any nagging doubts about the adequacy of the diet you are feeding your horse, consult your veterinarian.