Sugar content in horse feed
How does one define sugar?
Sugar, like starch, is a carbohydrate. The carbohydrates found in nature are mainly of plant origin and form a major component of the food of many animals.
Sugar is commonly understood to mean monosaccharides and disaccharides such as glucose (dextrose) and fructose (fructose). Monosaccharides, disaccharides and polysaccharides can be combined in a variety of ways. Carbohydrates are also divided into structural and non-structural carbohydrates. Non-structural carbohydrates, for example monosaccharides and starches, are absorbed by the body more quickly, and thus can cause rapid increases in blood sugar levels. Structural carbohydrates include hemicellulose, cellulose and pectin. These are found in the cell walls of plants and serve as “frame builders”. Sugar occurs naturally in plants through photosynthesis (the conversion of sunlight to energy in plants).
Starch is an important reserve carbohydrate in plants. Starch is found primarily in grains, potatoes and maize. But fructans also serve as intermediate energy storage for plants in temperate climate zones. Fructans are mainly stored in plant stems. Short grass can be quite rich in fructan. Because the plant grows less at low temperatures and temporarily stores more energy, it expends fewer fructans. The fructan content of the plants is highest in sunny, cold weather which caused generation of much fructan with hardly any of it expended. The fructan content of the plant is also subject to fluctuations depending on the time of day, due to varying temperatures, light intensities and reserves of fructan from the previous day. Fructan content also varies according to the type of grass. Grasses which have low fructan content include cock’s foot and timothy grass.
Fructans are considered a primary cause of laminitis. They are not broken down until they reach the horse’s large intestine and can there lead to imbalances to intestinal flora, with toxic consequences for the entire organism. Another fructan is inulin, found in the bulbs of Jerusalem artichoke, which is used in some animal feeds. Care should be taken that such feeds are not given to horses susceptible to laminitis.
Sugar content in roughage
Hay, too, also contains sugars. The amount of sugar in grass (and also later in hay) depends on the variety of grass, the time it was cut and environmental conditions during its growth. Such environmental conditions include temperature, light intensity and the availability of water and nutrients. Sugar levels will also depend on the species of grass and when it was harvested. High-performance grasses grown for livestock are unsuitable for feeding horses. These grasses are low in crude fibre and contain not only more protein and energy, they also have a substantially higher proportion of sugar, which is unsuitable for good doers and especially for horses susceptible to laminitis.
A sugar content of 10% is not uncommon in hay – on the contrary. Studies in Switzerland confirm this. In the canton of Valais, hay from the first cutting was analysed at different time periods (http://www.feed-alp.admin.ch/#). In hay from the first cut, sugar values were measured on average at around 100 g per kg of dry matter. The highest level was 180 g/kg of dry matter. It should however be noted that the sugar content was recorded with regard to dry matter – hay – and not the original substance (including its water content). This should be taken into account when different analysis values are compared to one another. Dr Romanazzi, in her own independent studies, has found similar results (http://www.offenstallkonzepte.com/versuche_zuckergehalt.htm). Here, values of even 150-200 g total sugar (including fructan) per kg of dry matter were measured.
What happens to carbohydrates in a horse’s body?
In animals, carbohydrates are transported as glucose and and stored as glycogen. Glucose in the blood allows for a steady supply of energy for the body. The hormone insulin forms in the pancreas in order to regulate blood sugar levels.
Monosaccharides like glucose and fructose need not be further broken down in the horse’s digestive tract, since they can be absorbed directly by the intestinal wall. Starch is most often the primary component of cereal-rich feed supplements. Starch is digested in the horse’s small intestine by amylase, an enzyme in the body. For instance, over 80 percent of the fine-grained starch in oats is digested in the small intestine. The digestion of course-grained starches like those found in maize and barley, however, takes place to a lesser extent there. By crushing or applying heat, however, starch's digestibility in the small intestine can be sustainably increased.
If the horse eats easily digestible carbohydrates such as high-starch concentrated feed, the blood sugar level will rise within a short time. This leads to a rapid release of insulin, which causes liver cells, muscle cells and fat cells to take up the sugar in the blood and store it as glycogen. If starch is not completely broken down in the small intestine, what remains is passed on to the large intestine. This starch will then be broken down in the large intestine by microbes. However, the feed as a high amount of starch, critical changes to the composition of the microbes will occur in the intestine (dysbiosis). These microbial changes can lead to serious digestive disorders and metabolic ailments.
Structure-forming carbohydrates such as cellulose, hemicellulose and pectins pass through the small intestine largely unchanged. These are then digested by microbes in the large intestine, resulting in volatile (short-chain) fatty acids which in turn are absorbed through the intestinal wall and supply the horse with energy. The horse's digestive system is designed for digestion of these plant nutrients through microbes in the large intestine. Horse feed containing crude fibre, which is low in easily-digestible carbohydrates, will cause the blood sugar level rise more slowly than a feed that is rich in starch and sugar.
A feed rich in starch and sugar leads to a high flooding of glucose and insulin in the body, which can lead to insulin resistance. This means that the tissue has a reduced reaction to insulin with the intake of glucose. Therefore, much more insulin must be released before it will have an effect. Regulation of the blood sugar is no longer fully functional long-term, leading to excessive sugar levels. This has consequences for the entire body. For example, horses with EMS are resistant to insulin.
Sugar in Agrobs Products
We at Agrobs indicate the starch, sugar and fructan contents of almost all of our products for horses, even though as feed producers we are not required to do so. For us it is only natural to provide an appropriate feed especially for horses with metabolic ailments.
Dr. med. vet. Katharina Boes
August 2016; AGROBS GmbH
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(* The references refer to the technical content of the text and not to the product recommendations.)