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Digestion

There is a saying that “you can kill with kindness”, and it is very true when we talk about how some people feed, overfeed or feed the wrong things to their horses.

It is not that they mean to hurt them, in fact, in most cases the opposite is true. Knowledge about horses’ digestive system is absolutely necessary if you are to make the right decisions about how much to feed and what to feed.

DigestiveTract

Remember, horses have evolved over 55 million years to eat and digest large amounts of cellulose fibre in growing plants. This provides the majority of their energy needs. Also, a horse’s natural diet in the wild has very little starch (found in cereals such as oats, corn and barley) and protein (found in clover and lucerne) so we need to be careful how much starch and protein we feed if we want to avoid major health problems. (If you wish to find out some do’s and dont’s of horse feeding go to ‘Feed & Pasture)

The beginning of the digestive system starts with the lips and ends with the anus and in between there are a number of stages. The sole purpose of this journey from the front end to the back end is to extract all the nutrients: carbohydrates, protein, fats, vitamins and minerals, which a horse needs to live and remain healthy.

Digestive Process

Let’s start at the beginning with the lips: If you have ever fed a horse from your hand you will know how flexible, sensitive and persistent their lips can be. They can brush aside unappealing food and delicately pick out the bits they like from their feed bin or select only the short green tips of grass while leaving the older stalks behind. The lips are a very well adapted instrument.

chewingOnce past the lips the front incisor teeth nip off the grass and the tongue pushes it back to the molars (cheek teeth). The food, having entered the mouth, is now at the first stage of the digestion process. The molars cut and grind food into smaller particles, using a side-to-side movement. A horse cannot grind its food sufficiently if it has a problem with its teeth so good tooth care is essential to good digestion. (See ‘Tooth Care’ for more information).

At the same time, lots of saliva (mainly water and mucus) is added to make it moist and slippery, making it easier to swallow. Saliva is only produced when a horse has food in its mouth, unlike humans who can produce saliva just by thinking about their favourite food! (See ‘Feed & Pasture for information about the relationship between saliva, dehydration and water consumption.)

When food enters a horse’s mouth it will need to move through about 30 metres of digestive tract before it emerges again as droppings. If you want to get an idea of how long that is, watch this video:

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This process can take up to 90 hours (usually 3 to 4 days) from beginning to end and at any one time, your horse can be digesting and processing around 170 litres of food. To find out what happens during that process, take a look at the videos on the digestive system at the bottom of this article.

What does all this tell us?

Horses must grind their food very well to help with digestion and the absorption of nutrient, so regular tooth care by an equine dentist or veterinarian is essential.

Large amounts of water are required every day so that the horse can produce enough saliva to swallow; the food material is wet enough to move easily along the digestive tract; water and electrolytes (salts) can be absorbed back into the cells so that the horse does not become dehydrated. Horses must have a continuous, adequate supply of fresh, clean water, 24 hours a day.

Horses are continuous feeders with a small stomach, so they need to be fed smaller amounts frequently (3 to 4 times per day if they are stabled with limited or no pasture time) rather than 1 or 2 large meals.

Horse’s stomachs are highly acidic and if left empty for long periods of time the acid will burn the stomach lining leading to very painful gastric ulcers.

The bulk of a horses diet should be made up of roughage from pasture or hay. Even horses in hard work, such as endurance, eventing and racing, should still have roughage making up at least 30% of their diet.

Great care should be taken when feeding grains (for example oats, barley and corn), or lucerne hay, or when allowing horses unrestricted grazing on spring pastures with high clover content. Excess starches and proteins may not be digested in the small intestine leaving them to ferment in the large intestine (hindgut).
This can lead to acidiosis and laminitis as well a variety of intestinal problems.

 

If you would like even more information about feeding horses we would recommend ‘Feeding Horses in Australia’ by John Kohnke BVSc (Hons) RDA (Hons), Dr Frank Kelleher BScAgr (Hons) PhD and Dr Penny Trevor-Jones BScAgr (Hon) PhD, published by RIRDC. Even though this book is for Australian conditions it is purchased all over the world as a universal text on horse nutrition.


Digestion Videos: