I often hear owners use the terms laminitis and founder interchangeably. But though the two ailments are certainly related, they are entirely separate in action and severity. It is important that we distinguish the two properly, when reacting to and treating our horses for sensitivity and lameness.
First, a quick lesson in internal structures of hoof:
Most of us know that the hoof capsule contains three bones; the coffin bone, the navicular bone, and the distal short pastern bone. Our focus with founder is in regards to the coffin bone, which serves to protect nerves and blood vessels, while providing an attachment for the deep digital flexor tendon. The corium is a vascular network that supplies blood flow to the hoof and surrounds the coffin bone. Along the dorsal side of the corium, we find it surrounded with a beautiful layer of sensitive laminae, which is itself surrounded by the insensitive laminae. The insensitive laminae continues outward to form the inside of the hoof wall. The two laminae are both made up of primary epidermal laminae and secondary epidermal laminae, and the vascular tissues are interlaced so strongly that they are quite difficult to pull apart! Together, they work to support the coffin bone and also the weight of the horse. Their health and integrity is essential to the hoof form and function!
I consider laminitis a symptom of disease and a precursor to founder. By common definition, laminitis is an inflammation of the sensitive laminae tissue inside of the horse’s hoof. But the Merck Veterinary Manual now describes laminitis as “a transient ischemia associated with coagulopathy that leads to breakdown and degeneration of the union between the horny and sensitive laminae.” Either way, the result is the same: the enter-laminae bonds become compromised and weaken, causing constriction of blood flow and a great deal of pain to the horse. In cases that are not managed or allowed to correct, these bonds can be completely destroyed and now the horse has foundered, causing the coffin bone to drop within the hoof. Founder is a mechanical event and a severe one, but it did not happen suddenly to the horse and it is rare that we see it take place in healthy, unrestricted hooves.
As a hoof care professional, I see evidence of laminitis more often than most owners want to acknowledge. While we should never ignore the signs of laminitis in our horses’ hooves and they vary in degrees of severity from extremely mild to very severe, I do believe we need to start looking at laminitis more calmly and with a better understanding of how common an occurance it is. From that composed and aware state of mind, we can analyze the general husbandry of our horses and start making appropriate changes for the betterment of their overall health.
Symptoms range from a fairly benign tenderness of the hoof to a more pronounced unwillingness of the horse to walk on its own or an insistence to stand in a way that shifts the weight off of their front hooves. In my experience, most owners entirely miss the mild symptoms of laminitis and this is unfortunate because here is your best moment to modify your horses’ husbandry before any further damage is done. Acute laminitis brought on by sudden climate or feed variations may last a few days or even a few weeks before subsiding, assuming the cause is eliminated or easily balanced. In healthy hooves, which belong to horses that are allowed the freedom to seek what they require (eg. standing at length in water, increased or decreased movement, change of terrain, change of diet) short periods of laminitis may come and go relatively unobserved and without lasting damage. I think of it as a fever of the hoof! The problem is that most of our domestic horses are not afforded those choices and so, problems increase in severity if we are not listening and making approprite adjustments. Chronic laminitis has been existing in the hoof for quite some time and the evidence is displayed in the hoof, whether or not the horse reacted strongly to it occurring. A hoof care professional can observe certain pathologies such as heels growing quicker than toes, divergent hoof rings which are wider or lower at the heel than at the toe, a straight hairline at the coronary band, and a stretched white line of the hoof. An owner may tell me “this horse has never taken a lame step”, but I can always see the truth displayed in the hoof. I usually see chronic laminitis when trimming obese horses, horses permitted only a very limited opportunity for movement, and horses consistently stabled in unvaried and static conditions. These horses are often in more trouble than the former and even without dramatic rotation of the coffin bone, their hooves will take more than a few cycles to rehabilitate.
What about wild horses? Many of us often look to the wild horse when considering how to better balance the health of our domestic horses. Do wild horses also suffer laminitis? The answer is yes!
In 2011, Brian Hampson, PHD, released a joint paper with Professor Chris Pollitt, documenting their extensive study of the feral horses throughout Australia. They gathered 100 horses from five distinct environments (20 horses from each) and collared them with GPS tracking devices after which a histopathology was conducted for several months, documenting by visual and radiograph, the left forefoot. Although the feral horses of Australia are not considered as a perfect model of the healthy horse, because they are not a native species and they must survive in environmental extremes where they did not evolve to exist, the team still came up with some interesting findings! In addition to the adaptability of the hoof to its environment and the profound effect each environment had on the hooves, they discovered that the incidence of chronic laminitis ranged from 40% and 93% (Hampson and Pollitt. Nov 2011. Improving the Foot Health of the Domestic Horse; The Relevance of the Feral Horse Foot Model.). Broken down by environment, the statistics look like this:
67% of the 15 rocky terrain horses were diagnosed with laminitis
40% of 15 sandy desert horses were diagnosed with laminitis
93% of 15 prime grazing terrain horses were diagnosed with laminitis
40% of 56 Kaimanawa region (New Zealand) were diagnosed with laminitis.
These horses were still thriving as much as they would have, considering the circumstances of their environment. Interesting to note that the horses living on the most lush vegetation have the highest percentage of laminitis. Horses did not adapt to live off of abundant amounts of rich feeds! Even still, the wild horses are generaly allowed the freedom to seek out what they require to heal and that is a significant difference between them and their domestic relations. Wild horses are certainly not on “stall rest” and they are not medicated, except by their choices of available vegetation. Their hooves, though they vary drastically from horse to horse and do not all represent what we think when we think of ideal barefoot hooves, remain unrestricted by shoes and are able to expand and contract upon weight bearing. They go through episodes of laminitis, but they are clearly able to manage and they are not foundering all over the range. Why? Choices, increased movement, unrestricted hooves.
In closing, I want to reiterate that laminitis while common, is still an alert to a greater problem that requires our attention! While some owners despair, I think we’re lucky the horse sends us an alarm! We then get our chance to look calmly at what might have spurred the incident (stress factors, toxins, change of feed, change of habitat, inappropriate feed, illness, etc.) and we get a chance to very likely fix the issue—not mask it, but fix it. Your horse is sending you a message. Accept it, keep your composure, build your team of equine professionals, and get to work solving the husbandry issues that are causing disease.
*When suspecting laminitis and evaluating your horse, don’t put so much trust in the common advice heat in the hooves being a diagnostic indicator. For one thing, barefoot horses are known to be more consistently warm in their hooves because their hooves are functioning as intended and the laminae are distributing energy actively and evenly. Blood flow can still be constricted in an incorrect trim or rehabilitating hoof, but usually the hoof is still performing better than it would be with shoes. In addition, so many environmental factors and activity levels can change the temperature of the hooves throughout the day. Using hoof wall heat as a diagnostic indicator will only be useful if you are aware of your horses’ normal average.
*You should only be using a digital pulse rate as a marker if you are already attune to your horses’ individual norm, at rest and at work. Horses vary. When we say a “increased digital pulse” is often an indication of laminitis, we are not referring to speed. We are referring to the strength and force of the pulse. This information doesn’t mean much unless you are already familiar with your horses’ pulse rate. Start practicing. They can be hard to find in a healthy horse with healthy hooves because the blood flow is not constricted! This site is excellent for teaching you how to find your horses’ digital pulse: http://www.ironfreehoof.com/equine-digital-pulses.html