We know that laminitis is a disease of domesticated horses. Horses in the wild that do get laminitis develop it more as a "concussion founder" from the stress and strain of walking over miles of rough terrain that can damage the hoof tissue, but in domesticated horses, we see laminitis due to other reasons.
Basically laminitis in domesticated horses relates to insulin, usually from feeding a genetically predisposed horse a diet too high in sugar and starch. But it is more than that: It has to do with the fact that the domesticated horses are subjected to things that they don’t have to experience in the wild. They are subjected to confinement, they’re subjected to stress—all kinds of stress, performance stress and travel stress--and then we put them on pastures that are generally one type of grass, oftentimes improved pastures. Or they stand for hours and hours on end, whether in a stall or in a small paddock, and this, too, can contribute to laminitis.
Regardless of the contributing factors, when we talk about laminitis, what we are talking about is inflammation of the laminae (the suffix I-T-I-S means inflammation). However, laminitis doesn’t start in the foot; laminitis starts elsewhere in the body; it’s a result of something going wrong someplace else.
Elevated insulin is probably the most critical and common cause of laminitis. The fact is that our horses typically eat too much sugar and starch, and they become too heavy and in many cases, they are also too sedentary. This may be difficult to accept, and yet it’s almost good news because if we know why it happens, we are able to fix it.
The second cause of laminitis, which is also very critical, is a systemic sepsis or poisoning due to the dying off of hind gut microbial population. Usually the bacterium involved for the most part is Streptococcus bovus, and this is generally caused by a grain overload where the starch bypasses the small intestine and ends up in the hind gut where the bacteria that live there will ferment it into lactic acid and that destroys the beneficial bacteria, leading to cecal acidosis.
Systemic sepsis can also happen from too much fructan in the hay or pasture. Fructan is a nonstructural carbohydrate. It is made of many fructose molecules that are linked together, but the horse does not have the digestive enzymes needed to digest it down to fructose for the most part and so most of that fructan then ends up in the hind gut where it, too, can be fermented. When these endotoxins reach the hoof, they themselves don’t really cause the problem; what happens instead is that they cause an overactivity in specific enzymes called matrix metalloproteinases (or MMP for short). These enzymes are important for normal tissue growth and repair, but when they become overactive, they can become destructive. That’s a major consequence of systemic sepsis.
Laminitis is complex and there are other factors that can lead to a laminitic episode: injury, infection, retained placenta, trauma, sustained physical demands on the feet, emotional stress from a non-injury accident, hospitalization. Even overloading certain nutrients and minerals, such as selenium and iron can also lead to laminitis.
Regardless of the cause, however, inflammation is always present in laminitis. The materials below will help you gain a better understand of this painful condition, how to prevent it, and how to manage it if your horse is prone toward developing it.