Care must be taken when feeding cereals as the horse's digestive system can only handle so much starch at once. The stomach of the horse has a very limited capacity (the size of a rugby ball).

A small amount of starch digestion occurs here before the food enters the horse's small intestine where the majority of starch digestion occurs. Rate of passage through this, the foregut of the horse is fairly rapid (1-6 hours).

On top of this, the horse produces limited amounts of the enzyme that digests starch (amylase); in fact the horse only produces about 10% of the amount of amylase that a pig produces.

Essentially this means that the horse has a limited capacity for digesting cereals and should, therefore, not be fed large amounts of starch in any one meal.

The rule of thumb is that horses should be fed no more than 2kg of concentrate at any one time.

However, for some horses, this maximum meal size needs to be less and a good safe level would be to feed no more than 1.5kg in any one meal. Any overspill, due to overlarge meal sizes, means that undigested starch will pass into the large intestine where fermentation of it will occur by starch digesting bugs in the horse's hindgut. When this happens the pH drops and the good, fibre digesting bacteria population will be killed off, leading to the proliferation of bad bacteria and the production of toxins.

Ironically, this upset in the gut balance will mean that the horse is unable to digest and make use of much of the energy provided to it by its well meaning owner, as well as increasing the risk of colic, ulcers and other digestive problems.

Oats are the traditional cereal grain for horses and are the best choice for several reasons.

To begin with, oats are palatable and are the best nutrient-balanced grain, containing about 53% starch, 12% protein, 5% fat and 12% fibre. They have the highest fibre content and lowest energy of all the grains, making them the safest to feed.

More importantly, the starch in oats is easily digested (83%) by enzymes in the small intestine. Therefore, oat starch doesn't contribute to starch overload in the hindgut like maize and barley starches.

It's a commonly held belief that oats send all horses sky-high. In fact, as with any concentrates, if they are fed in proportion to the level of work actually being done, rather than anticipated, oats rarely cause a problem.

Many horses can eat large quantities of oats without any problems, while only a few who are sensitive will react in the ways we typically imagine.

It is starch that causes the 'heating' effect, as it is broken down rapidly into glycogen and then glucose. These sugars are absorbed very quickly, giving the horse a rush of energy.

While most horses are not affected, a few react by becoming excitable. This is as likely, if not more so, to occur with maize and barley (which are both higher in energy) as it is with oats.

Barley, which contains about 65% starch, has a hard kernel that horses cannot easily chew, so it is usually bruised.

However, even in bruised barley, when fed as a straight, the starch has a low pre-ceacal (pre-hindgut) digestibility (about 21%) in horses, which means that most of the starch enters the hindgut, leading to acidosis and possible problems with laminitis, ulcers and colic.

Therefore, as a straight feeding stuff, oats are a safer choice for horses than barley.

Simply cracking, rolling or bruising grains is essentially the same process as chewing and aims only to change the physical structure of the grain, breaking the seed coat and reducing the grains particle size to give the enzymes better access to the starch within the centre of the grain.

Physical processing results in only small improvements to starch digestion. Work conducted in horses showed that cracking maize only improved its digestibility in the small intestine of the horse by 1%.

Grains are cooked (eg micronized, extruded, cooked and flaked and during the pelleting process) using a combination of heat, moisture, pressure and some form of physical process like rolling or grinding.

Due to this processing the structure of the grain is entirely disrupted, which gives the horse's enzymes access to the grain starch so they can break down the starch into glucose, which the horse then absorbs from the small intestine into the body, where it is used for energy.

This processing reduces the chance of undigested starch entering the hindgut and causing the problems stated earlier. This is why all cereals, except oats, should be fed in the cooked form only.

Contact: Harbro Limited

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