There are a number of golden rules when feeding your horse, here are some of them and the reasons why...
Feed little and often; this is due to the horses evolutionary characteristics, the horse has evolved to be a "trickle feeder". It is a constant grazer and has a small stomach capacity of 8-15L, this should only be half full at any one time. The pyloric sphincter controls the food leaving the stomach and only lets food through slowly so the stomach gets full quickly if the horse has eaten a large meal. Concentrates should therefore be split into smaller meals. It is also important the horse has ad lib forage. If a large concentrate meal is fed that is high in starch it can lead to problems such as colic and laminitis.
Feed plenty of fibre; this will encourage peristalsis (the movement of the food through the gut). This will mean complete mixing with enzymes and microbes will take place. High levels of forage slows the passage of digesta through the small intestine compared to grain, as grains take 15 mins but forage can take 10 hours to pass through. This is the best place for food to be digested as it is slowly done by microbes. A horse on forage is less likely to have digestive problems as this is the feed their gut has adapted to digest. The small intestine is very long so the digesta has plenty of time to be digested and adsorbed here. Grains disturb the secretion of hormones such as insulin, this can be due to glucose peaks. Fibre causes a more consistent concentration. Insulin effects other hormones such as growth hormone and thyroid hormone. If a high grain diet is fed it can also have effects on the horses behaviour. Acid will rise in the stomach and can cause stomach ulcers. This has been linked to crib biting. The absolute minimum of fibre given to a horse is 50% of the feed, but 100% is the best.
Make changes gradually; this is done as sudden changes can lead to colic, especially a change in cereal: forage ratio. Changes should be made in over two weeks as they are more likely to get colic in this time period. More care has to be taken when dealing with a high levels of concentrate due to the starch. This is because the microbes in the gut play a large part in digestion and adapt to what the horse is eating. Therefore they will not be able to cope with a sudden change and will not be able to digest the food. This can lead to problems such as laminitis.
Provide a fresh, clean water supply; they should have access to as much water as they want. Water is by far the most important thing that a horse needs. If it isn't clean them some horses may chose not to drink it.
Do not ride immediately after feeding your horse; you should allow an hour after feeding before riding. This will give time for the food in the stomach to be digested before they are ridden. The blood supply will be rich in the stomach area whilst digesting foods but during exercise the blood will be diverted to the muscles.
All of these rules are important when feeding your horse. Trooper's diet is almost fully forage as he has hay and grass and in his feed he has Happy Hoof which is made up of chaff. He only has a small amount of Winergy Ventilate and a biotin supplement on top of this. Trooper does get fat very easily so he has to have a restricted amount of hay in the stable and has his hay nets double wrapped so it takes long for him to eat it!