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<p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif;"><i></i><em><span style="line-height: 115%;"><em>The article is written by Dr. Dag Austbø at the Norwegian University of Life Sciences institution. Dr. Dag Austbø and Dr. Knut Hove are two of the key people behind the development of PC-Horse. Their scientific work and international networks contribute to the continued development of PC-Horse and to secure that our calculations are based on established scientific data.</em></span></em></span></p>
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<p>&nbsp;The horse's ration consists either of roughage only (grass, hay or silage) or of a mixture of roughage and concentrates. A concentrate feed can consist solely of grains, such as oats and barley , or of concentrate mixtures that may contain several different ingredients such as oats , barley, corn, wheat (grain species) or other feeds such as beet pulp (with highly digestible fibre) , lucerne , soybean meal (a protein supplement) and vegetable oil (fat). Minerals and vitamins are commonly added to compound feeds.</p>
<p><img alt="Stärkelse havre" src="images-joomla/stories/seasons/Stärkelse_havre.jpg" height="392" width="550" /><br /><br />In a compound feed, the various raw materials (especially grains) may have undergone feed-technology treatments, which, in addition to grinding, include heat, pressure and moisture. For grains, this is done mainly to increase the digestibility of starch.<br /><br />The horse is by nature a grass eater that does not obtain much starch directly from the feed itself. Nevertheless, it does have enzymes (amylase) in its small intestine to digest starch. The activity of these enzymes is lower than in animals more adapted to rations with higher starch content.<br /><br />Starch consists of large molecules that are broken down into simple sugars (glucose) by enzymes in the equine small intestine. This causes the horse's blood sugar (glucose) to rise considerably after meals containing starch. Blood sugar is regulated in the horse, as in man and other animals, by the activity of insulin.<br /><br />If we compare the amylase activity in the small intestine of pigs and horses, horse values are less than 10 % of those found in pigs. This means that there are limits to the amount of starch a horse can digest enzymatically in the small intestine. Too much digestible starch absorbed in the small intestine can cause muscle stiffness (tying up) and, in the worst case, rhabdomyolysis . There are individual differences between horses in the amount of starch they can tolerate in their ration. In general, ponies tolerate less than riding horses, trotters and thoroughbreds.<br /><br />Starch that is not digested and absorbed in the small intestine enters the caecum where the gut microbiota converts it into short-chain fatty acids (mainly acetic and propionic acid) and lactic acid. If too much starch is delivered to the caecum, it can cause imbalance in the microbial populations, a decrease in the pH value of intestinal contents and an increased risk of diseases such as colic and laminitis.<br /><br />When considering the amount of starch in rations for horses, we must take into consideration that the starches from different types of grains have different levels of digestibility. Generally, starch from oats is easily digested by the enzymes in the small intestine. Starch from barley, wheat and corn are significantly harder to digest in the small intestine. To improve small intestinal digestion of these starches it is common to grind the feed and additionally treat it with heat, pressure and steam. In the modern feed industry, these methods are widely used.<br /><br />A typical content of starch in maize is about 670 grams per kg. In barley it is about 500 grams per kg and in oats about 350 grams per kg. In compound feeds it can vary from 380 to 200 grams per kg.<br />When assessing the effect of starch in horse rations, we must take into account several factors. First we need to consider the type of horse, pony or big horse. We also need to know if the feed has undergone feed-technology treatment that alters its starch digestibility.<br /><br />A reader of all this may conclude that it is dangerous to feed horses with starchy concentrates. Normally though, this is not the case. Throughout the whole of history, grains have always been included in horses' rations. Grains have given them the extra energy needed to serve man in agriculture, transport and especially in war. Today, activity in sports and competition means that horses must receive additional concentrates to meet their increased nutrient requirements.<br /><br />How should we feed the starch-containing concentrates to avoid a negative impact on the horse's health? The most important factor in this regard is to control how much starch the horse receives in each meal. A normal recommendation is that the amount of starch per meal should not exceed 1.5 grams per 100 kg body weight. This means that a horse of 500 kg body weight should not receive more than 750 grams of starch per meal. When using the PC–Horse program to set up your rations you get an overview of the total amount of starch in the actual ration. If you distribute the daily ration into meals (choose Meal Chart) the amount of starch per meal is calculated and you will be notified if this is too high. You must then either change the ration or increase the number of meals per day.<br /><br />If you always use PC -Horse to formulate your horse's rations you will be able to control roughage and concentrate quantities and ensure that amounts are in accordance with recommendations. This will ensure the most balanced and safest feeding for your horse(s).</p>
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<p><strong>What does this mean in practice?</strong><br />Daily intake of roughage varies based on feed quality, production classes, individual appetite and each individual's place in the herd hierarchy. This means that we must observe horses in a herd closely and make corrections to the feed offered each individual at night-time or early morning to avoid some individuals growing too fat or too thin.</p>
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