Founder or Laminitis is one of the most common causes of lameness in horses that we see as vets. It is a complicated disease process. For whatever reason that physiology of horses does not see blood supply to the hoof as a high priority, so when demands are made on the blood supply, e.g. for pregnancy or illness or stress, blood tends to be directed to these organs and away from the hooves. In summary, founder results when blood supply to the hoof is impaired, this leads to a breakdown of bond between the sensitive and non-sensitive part of the hoof (a bit like our nail quick), once this bond id damaged the bone at the tip of the leg can be forced through the sole of the hoof. In its worst form this pedal bone can be seen when you left up the hoof, the animal is in constant pain, will never recover and has to be destroyed.
The usual cause of founder in the horse is dietary overload. It is most common in fat ponies on good pasture or after any horse engorges on grain. This is why we vets take so seriously the case of the horses that have just broken in to the grain shed or discovered a grain spill. Firstly they could die of acute colic, should they survive this founder is a very common consequence. These horses to be treated very aggressively with paraffin oil to dilute the grain, drugs to “keep the heat out of the feet” and other treatments to stop colic, rehydrate them and so on. Signs of grain founder usually do not appear for 12 to 18 hours after ingestion. Death can rarely occur due to acute founder and in severe founder the hoof can slough off.
There are many causes of founder besides diet, for example a mare can founder within hours of retaining an afterbirth (unlike cows this problem in horses should be treated as an emergency), a horse can get “road founder” due to galloping on hard ground, indeed any severe illness can interrupt the blood supply to the hooves and cause founder.
Animals that have acute founder will be lame, epically in both front legs as these are invariable worse affected than the back legs, reluctant to move, stand leaning backwards and walk on their heels. This is because the worst pain in the foot is in the sole over the toe region, where the pedal bone is pushing down. The horse will keep shifting its weight from foot to foot, may lift its feet or lie down a lot. People often mistake the signs for arthritis. As the condition becomes chronic hoof growth is often affected. The constant pressure brought by the walking on the heels will make them grow faster than the toe and a “slipper hoof” will start to form, in its worst form these can overgrow in a big curl like a ram’s horn. If the pedal bone starts pushing through the sole a bulge becomes obvious in the toe region of the sole.
Time is the essence in treating acute founder, the sooner the better.
Treatment during the acute phase of laminitis is aimed at removing the cause e.g. reducing weight, removing grain in diet, removing afterbirth and remaining the blood circulation to the hooves. The hooves of a horse act as pumps to send blood back up the legs to the body. They are spongy and as they strike the ground the blood is pumped out. With founder the blood does not find its way into the millions of tiny vessels, this starves the hoof- soft tissue bond of blood and it breaks down. Because the blood is not going into these vessels during acute founder the digital arteries at the side if the pastern having bounding pulse and the feet will be warm to touch. Pain plays a big role in the founder disease process; if we can relieve the pain of acute founder then the circulation to the hooves will improve. Remember the horse’s blood system does not see the hooves as a priority so when they have colic or a retained afterbirth or etc., their body tends to redirect the blood from the hooves to the organs. Whether or not the horse should be forced to exercise is a common question. Some exercise is good to keep the blood flowing in the hooves, but too much could force the pedal bone to rotate and increase the amount of pain with all its consequences. It is considered beneficial to provide short periods of exercise, IE 10 minutes per hour. Other things like standing the horse in cold water are of questionable benefit. Putting the horse in a stable filled with soft sand has been found to work well.
Hoof care is important in treating founder. There are special shoes called heart bar shoes or alternatively rubber ‘lily pads’ that can be applied to the hoof. Both these aim to take the animals weight more on the heels and frog rather than the toe and sole.
There are many secondary effects to founder. Slipper- hoof has already been mentioned. Foundered horses or horses prone to founder need attention of a well-qualified farrier if you are going to continue to use them. They tend to develop hard brittle hooves that are shelly and crack easily. You can often see where an episode of founder has occurred by a “ring” on the hoof like the rings a tree develops during drought. The sole of a foundered horse will often become chalky and weak, the white line which marks the boundary between sensitive and non-sensitive hoof will often break and spread after foundering. This allows mud and dirt to be packed up into gap, smelly thrush- like infections can occur, this is called “seedy toe”; in its worst form the whole hoof or sole can be completely under run by infection, sometimes sections need to be cut out of the hoof to allow drainage and antibiotics may be required.
The combination of bone rotation and hoof changes in a foundered horse can be frustrating lameness that comes and goes, epically at a trot and on hard ground. The horse can be having problems many months after the incidence of founder. Treatments like Biotin and methionine supplementation and hoof ointments as well as farriery can help. It may be best to have x-rays take to evaluate the degree of pedal bone rotation, allowing a better prognosis and long term approach to therapy.
Prevention of founder is obviously best. Keep those fat ponies not so fat, start locking them up when they are obviously overweight and their crest is getting big, by the time it is “lumpy” they have probably foundered. Be cruel to be kind. Founderguard is an antibiotic granule that can be fed to horses to stop founder from professional vet care as soon as possible, it is one of the worst diseases of the horse.
Summary of treatment
- Visit the vet as soon as possible to diagnose the problem, possibly x-ray and investigate course of treatment
- Diet and Founderguard. NB get vet advice before starving a pony
- Painkillers e.g. “bute” sachets
- Exercise, graded as recommended
- Farriery. Possibly heart bar shoes or lily pads. Needs on going care
- Biotin and other hoof supplements to improve the health of new hoof growth
- Hoof dressings such as hoof- aid and iodine soaks. Keep soles cleaned out
- Other treatment e.g. antibiotics for “seedy toe” recommended
- Revisit reassesses & checks no permanent damage