Laminitis – A Lesson in Anatomy
In order to define laminitis, it is important to understand the internal structure of a horses hoof.
The last phalanx, or the coffin bone, is suspended within the hard hoof capsule by finger-like structures called laminae. One set of laminae arise from the inside of the hoof wall, and the other from the coffin bone itself. The two sets of laminae interdigitate with each other and act to spread out the forces from the skeleton of the horse as the horse moves.
Inflammation in this area can lead to a breakdown of the union between the hoof wall and the laminae, leading to rotation of the coffin bone. Any slight rotation of this bone causes the horse great pain and must be identified in order to be properly treated.
Causes of Laminitis
The most common causes of laminitis are grain overload, grazing of lush pasture grass, and excessive concussive forces on the feet. In addition, excessive use of certain steroid drugs, colic, and post parturient metritis (retained fetal membranes in a mare) can all be causative factors of laminitis.
Overweight and obese equids are also prone to laminitis because these ponies and horses tend to be insulin resistant, leading to consistently high circulating blood sugar content. Ponies and other hardy horses that have evolved to survive in harsh environments with only sparse grass tend to become more insulin resistant when fed the same feed as a light bodied horse. Insulin resistant horses may become laminitic from only small amounts of grain or high sugar grass.
Does My Horse Have Laminitis?
Although laminitis may certainly affect all four feet of the horse, it more commonly affects the front feet. Horses influenced by pain from laminitis will develop a typical “laminitic stance” with forelimbs stilted in front and their hind limbs underneath the body in order to take weight off the toes of the forefeet. The horse may also lie down for longer than usual and walk with a “pottery” gait to avoid keeping weight on only one forefoot at a time.
Other signs of pain include sweating, flared nostrils, and muscle tremors. A bounding pulse will be felt in the blood vessels at the back of the fetlock, indicating the inflammation present in the hoof.
In cases of laminitis which have been long standing, “laminitic rings” may be seen on the exterior of the hoof because laminitic changes within the hoof capsule lead to alterations in the growth pattern of the hoof wall.
If you suspect you horse may be suffering from laminitis, it is crucial that you inform your veterinary surgeon in the early stages of the disease so that a diagnosis can be made and treatment may be implemented.
If laminitis is suspected, your vet will take a simple set of x-rays of the feet to properly assess the degree of rotation, sole thickness, dorsal wall thickness, and sinking of the pedal bone. Based on the findings, a prognosis will be made. If laminitis is identified in the early stages and treatment is aggressive, there is usually a good prognosis and the horse may make a complete functional recovery. However, the prognosis gets worse if the laminitis is severe or is complicated by Metabolic Syndrome, Cushings disease, or is a result of toxins in the blood from other conditions. Based on the x-rays, if the horse has evidence of sinking as well as rotation of the pedal bone or solar penetration by the pedal bone, the prognosis is worsened.
In order to make your horse more comfortable, your vet may apply frog supports to take the weight off of the tip of the coffin bone and distribute the weight through the frog instead. This is a simple measure, and a rolled up bandage can be placed over the frog and secured with duct tape.
Remedial shoeing is also utilized in some cases, and is based on support of the frog as well as changing the break over point of the hoof to put less pressure on tip of the coffin bone. It is important that the vet and farrier work together to discuss therapeutic shoeing options.
Veterinary drugs such as Phenylbutazone (bute) or suxibuzone (Danilon) may be prescribed to painful horses, and will also act as a powerful anti-inflammatory. Vasodilators, such as acepromazine (ACP), can be given to improve laminar blood flow. ACP also has a sedative effect which reduces movement and therefore concussion on the hooves.
Cold hosing or applying ice packs to the hooves and coronary band may in some instances prevent worsening conditions by helping to relieve some inflammation, but is best in combination with medications and frog support.
Feeding the laminitic horse is a science. Ideally, feed a diet which is high in fiber, low in carbohydrates, has a good quality protein, and a supplement to ensure all nutrients are available. The Laminitis Trust is a wealth of information when trying to weed out the good feedstuffs from the bad, and their logo can be found on feeds which they have approved for laminitic horses and ponies.
To Treat or Not to Treat
Treatment can quickly get very expensive, and as an owner, finances must be taken into account when deciding on any treatment protocols. Animal welfare is also an important consideration, and although there are many drastic surgical and interventional approaches available, sometimes it is not correct or fair to put a horse through these things. Finally, discussing all of the options with your vet is vital to making a decision which is right for your horse.
Preventing Laminitis in Your Horse
Like many things, prevention is the key. There are a few management related things that you can do at home to ensure you take the steps to help prevent laminitis.
Maintaining your horse at a healthy weight through a reasonable diet and exercise routine is critical to prevent laminitis. About 80% of UK horse owners do not realize that their horses and ponies are overweight, because they do not know how to properly assess the bodyweight of their horses. You can learn to assess body fat cover with various charts and videos from World Horse Welfare and the Laminitis Trust, or you can ask your vet to body condition score your horse for you and recommend an appropriate diet based on your horses level of use.
Mechanical laminitis may occur in horses with long toes undergoing excessive concussion on hard surfaces, such as frozen ground or tarmac. Long toes cause a delayed break-over, causing mechanical separation of the laminae at the toe. Excessive concussion can be likened to hitting your thumb with a hammer, and resultant pain associated with a blood blister trapped underneath the nail. To prevent this, stick to light hacks while the ground is hard, or limit exercise to a school with soft footing.