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In grain founder, for instance, the starch in the grain creates a prime environment for overgrowth of bacteria in the gut, if the grain gets into the cecum and large colon before it is completely digested (and this is what happens if the horse eats too much). The fermentation and rapid multiplication of bacteria leads to production of endotoxins that can compromise the gut lining and leak into the bloodstream, where the toxins are carried to the horse's feet to damage the laminae and their blood supply. According to Dr. Rodney Belgrave, Equine Internal Medicine, Washington State University, the endotoxin itself is a component of gram-negative bacteria--their cell walls. When these bacteria multiply rapidly and then die off due to the increased acidity of the hindgut, the endotoxins have severe adverse effects on the cardiovascular system. Laminitis is still somewhat of a mystery as to the actual causes, and there are a multitude of treatments. Usually in veterinary medicine, whenever there is a disease that has a long list of treatments or potential treatments, this means we don't really know how to treat it (though some things may help). When it comes down to the bottom line, all cases are somewhat different and some treatments work for some horses and not for others. "This is often hard for people to understand," he said. "Veterinarians are also frustrated; when we try to treat horses with laminitis, some respond, and whether or not it's due to what we did, or to the fact they would have gotten better on their own, we don't always know. "Some treatments are recommended, just because in some cases the horse got better. I've used a treatment on a horse and it worked, and have used it on another and it didn't work. So all individual cases are different. This makes it very frustrating because there are so many different ways to deal with laminitis." The "something" in green grass which causes founder was recently discovered to be sugar. Grasses store energy in their seed heads as starch (the biggest starch-storers are the cereal grains) but researchers in Wales found that grasses also store energy in roots, leaves and stems as fructan, a type of sugar. Thus grass founder falls under the category of carbohydrate overload; lush, fast-growing grass serves as a source of highly digestible, high-energy feed. Whenever grass is growing rapidly, the plant may produce more energy than it needs, so it stores the excess as fructan (which can be converted back to growth energy at night or on cloudy days when the plant is short on energy). In the spring, or whenever the weather brings sunny days and cool nights, grass plants store large amounts of fructan in their lower stems (for use at night) and may create more than they use up at night. In summer the plant has less fructan reserves because most of the sugar produced by the plant during the day is used up each night. Thus horses are less apt to develop grass founder during summer. Eating excessive amounts of fructan can lead to laminitis, just as consumption of too much starch (in grain) can cause problems. Some of it passes through the small intestine undigested and is then fermented by the bacteria in the hindgut (cecum and large colon). This creates lactic acid and bacterial toxins that trigger the laminitis. Contents of the large hindgut become acidic due to excessive fermentation, resulting in death of large numbers of gram-negative bacteria and subsequent release of endotoxin. In part two we discuss prevention of grass founder.
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