If you have been warned about too much starch in a meal, you should distribute the concentrates and grains in the ration throughout the planned meals, and introduce more meals if necessary. You can also try to replace some of the concentrates with roughage (hay, haylage, beet pulp) of good quality. You can read below more about starch and how this feed component is digested.
Starch is a carbohydrate found in plant seeds and roots, such as grains or potatoes, and is an energy reserve for the plant. For comparison, animals use fat as their energy reserve. Starch is the most energy-rich part of the grain. The content of starch in oats and barley is about 500 g per kg (50% of the weight), and there is slightly more starch in barley than in oats.
Digestion of starch in the horse
We want as much as possible of the starch to be digested and absorbed in the small intestine. Starch which is not digested in the small intestine will be passed on into the caecum, which is very large in the horse. Here, starch may create imbalances in the microbial flora and lead to a fall in pH and a reduced digestion of fibre.
The chemical and physical structure of starch varies between grain species. The starch in oats is more easily digested than starch from barley and maize. This has practical significance for the horse because the horse can digest more oat starch in the small intestine than starches from other cereal species. When barley and maize are treated with pressure and heat, as is common in the commercial production of feed mixtures, the starch becomes more easily digestible, and behaves more like oat starch in the digestive tract.
Glucose is produced when starch is cleaved by several enzymes in the small intestine, and is then absorbed into the blood. A meal of cereals will in just a few hours give the horse elevated blood glucose (blood sugar) concentrations. Blood levels of glucose are regulated by the hormone insulin. Increased secretion of insulin takes place after a meal, and the hormone promotes the storage of glucose in the form of glycogen in liver and muscles. Glycogen is an important energy store for the horse, and is mobilized quickly when needed, for example during strenuous exercise and competitions.
Horses are sensitive to variations in blood sugar. Some horses, especially ponies, may have trouble regulating blood sugar (a form of insulin resistance). Some horses may also become excited if the blood sugar concentration rises quickly (heating). It is therefore important, when planning feeding, to consider the amount of starch each horse will receive at every meal.
Because of its properties, starch is both an important source of energy in the horse's ration, and also a feed component that can cause adverse reactions in the digestive system. As mentioned earlier, we do not want too much undigested starch to arrive at the caecum. At the same time, we do not want the starch to be too easy to digest, since this will give rise to excessive increases in blood glucose levels. It is therefore important to have a good grasp of how a starch-rich ration affects your horse, and how you can achieve a digestion profile for the starch that balances the two effects mentioned above. With PC-Horse you have the means to ensure that the amount of starch contained in each meal is within the recommended limits.
In normal healthy horses, we recommend that a single meal should not contain more than 1,5 grams of starch per kg body weight. This means that a horse weighing 500 kg should not get more than about 750 grams of starch per meal. Since cereals and grain mixtures contain 400-500 grams of starch per kg, you should not give more than about 1,5 kg of grain or concentrate mix per meal. If your horse has a high energy requirement and receives a high proportion of grains and concentrates in its diet, we recommend increasing the number of meals per day, or changing the distribution of feed between meals if you become aware that the amount of starch per meal is too high.
In PC-Horse, you can distribute the horse's overall ration over individual meals. You will then be given a clear warning when the amount of starch in one or more of your meals exceeds the recommended limits. For horses that have trouble regulating blood sugar, or easily develop symptoms of "tying up", it will be beneficial to provide less starch per meal than the recommended 1,5 g/kg body weight. As an alternative you can feed vegetable oil (see below), thus reducing the amount of grain or concentrate mix in the ration, without depriving the horse of too much energy.