All About ... Carbohydrates

A while ago I wrote a blog about 'what is in our horses food' , I mentioned that carbohydrates provide the energy for all cell processes and basic functions and so should be the main source of energy for a horse.  

Carbohydrates come in several forms; sugar, starch and fibre - such as cellulose.

Monosaccharides are the simplest form of sugars, they are made up of just one unit so sometimes are called simple sugars.  Glucose, fructose, xylose and galactose are all monosaccharides.  Each gram of glucose gives approximately 16kj of energy when broken down during cellular respiration.

Disaccharides have 2 units of sugar which are bonded together, lactose, sucrose and maltose are all disaccharides.  Lactose is comprised of 1 unit of glucose and 1 unit of galactose, sucrose is 1 unit of glucose and 1 of fructose. Sucrose is the most common sugar in plants eg: grass.

Oligosaccharides are made up of between 3 and 10 units of sugar.

Polysaccharides  are made up of many more units and are also called complex carbohydrates.  This group includes cellulose and starch and they do not taste sweet and are not soluble in water, unlike glucose, sucrose etcetera.   Starch has to be broken down into glucose before it can be used for cellular respiration.  Fructans are made up of many fructose units.  Plants store their excess 'sugar' as fructans in the leaves and stems and as starch in the seeds.  

Carbohydrates, which a horse consumes in the form of forage or grain are mostly broken down in the small intestines.  Disaccharides and starch are broken down in to monosaccharides (glucose) before being absorbed into the blood stream to be taken around the body.  The glucose is then converted by the cells to energy they can use to perform their functions!  If a horse eats too much starch it cannot all be broken down by the enzymes in the small intestines.  Any undigested starch will therefore move into the large intestines, where the bacteria are not generally used to digesting starch. 

The structure of cellulose is so complex that it cannot be broken down in the small intestine, this travels on to the large intestine where it is partly digested by fermentation to produce volatile fatty acids which the horse can use to produce energy (see next week's blog).

Where to find them:

Lactose is the sugar found in milk, so a foal will receive this easily digestible form of carbohydrate from its mother's milk.

Starch is found in cereal grains such as: oats, barley, maize and molasses  (the seeds of the plant)- these are called 'concentrates' because they contain a concentrated amount of usable carbohydrate.

Forages such as: grass, hay, alfalfa and chaff - will contain some monosaccharides but are mostly made up of polysaccharides like cellulose.  This means that they contain far smaller amounts of usable carbohydrate.

However, these cellulose rich feeds are more important to a horses' health than cereal grains, because a horses'  digestive system has evolved to cope with grass and other sources of fibre.  High starch and/ simple sugar diets will cause increases in glucose in the blood which most horses are not able to cope with.   See my feeding blog for more about this and our horses food.

Did you see this week's video 'Getting colder'  on my You Tube channel?   
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Until next time!

Jo