With all the things we hear and read about cutting our carbs we automatically assume that these things apply to our horses too. When in fact, carbohydrates are a fundamental part of any horse's diet and therefore cannot be cut out of their ration. Carbs should make up anywhere from 55 to 75% of a horse's diet. So this means that we really need to understand the way carbs are broken-down and metabolism when making our horse’s ration.
Firstly, carbohydrate (CHO) is a chemical term that describes any compound that is composed of hydrogen, carbon and oxygen in the general formula - CH2O. The terminology of CHO can get very confusing: simple sugars, mono and disaccharides, simple and complex CHO, soluble and insoluble CHO, polysaccharides, starch, fibre and etc. Part of the confusion is because your digestive tract is very different from your horse’s, so, using the same human understandings, trends and definitions for CHO in relation to your equine companion usually doesn’t match up.
Basically speaking, CHO in your horse's ration can be grouped into two main groups:
1) Sugars and starches categorized as non-structural CHO (NSC)
2) Fibre known as structural CHO. (we’ll address fibre in Part 3)
Now this is going to get a little technical - starches and fibers and sugars in starches bond together differently. Sugars in starches are linked with alpha-1,4-glycosidic bonds, where as the sugars in fibre are held together by bata-1,4-glycosidic bonds. I know this is extremely boring and scientific, but, this small difference is fundamental in understanding the breakdown (digestion or fermentation) of these two separate types of CHO. Digestive enzymes produced by your horse can only break the alpha-bond, and only the microbial enzymes found in your horse’s hindgut are capable of cleaving the bata-bond. In other words, the major difference between these two groups is that starches are digested (generally) in the small intestines and fibre is fermented in the hindgut.
Simple sugars (mono & disaccharides) are the only form of CHO that can be absorbed in the small intestines. Starches (polysaccharides) must be broken down by your horse's digestive enzyme before being absorbed into the blood primarily as glucose. Preferably, most of the starches within your horse's diet should be absorbed within the small intestine. However, this is not always the case since your horse’s ability to digest starch is very limited.
Five factors have been identified to influence starch digestibility in the small intestine:
1. Source of starch
2. Processing of starch
3. Amount of starch intake per feeding
4. Time of hay feeding in conjunction to grain
5. Individual differences between horses
We'll take a closer look at these factors in next week's blog, Part 2.