The popular saying, " A horse is only as good as his feet and legs", has been around a long time. It still applies today. All of the varied uses man has for horses, even breeding, require a horse to move around with a reasonable degree of comfort. The horse has survived the centuries by running from danger. The three-legged ones didn't make it. So lameness is a serious problem.
One cause of lameness is founder or laminitis. The two terms are used interchangeably, although, to me they have different definitions. Laminitis means inflammation of the sensitive lamina of the foot. This is the tissue that connects the coffin bone to the hoof wall and sole. Founder implies some incident that can lead to laminitis, but also may involve the entire body in some cases. Eating too much grain, drinking too much water when hot, and allergies to various feed or drugs are examples of incidents, which can cause founder. These things can cause a horse to be generally sick as well as causing laminitis.
There may be no one in the world that totally understands what happens to the foot when a horse founders. It is a complicated disease condition and sometimes there may be no apparent cause.
A general simplified explanation might go like this. A horse eats or is exposed to some substance, which causes an allergic response. Part of the body's reaction is to release histamine into the circulation. Histamine in large enough doses causes different reactions in different parts of the body. In the lungs it can constrict the bronchioles and cause difficulty breathing as in a child with asthma. In the skin it can cause bumps referred to as hives. In the horses foot it can cause swelling of the sensitive lamina. The hoof wall on one side and the coffin bone on the other encase the problem here is there is no room for the lamina to swell since it. This results in a great deal of pain; the horse acts like it is walking on eggs. When the reaction is severe enough, the loss of blood supply caused by the swelling can result in laminar tissue dying which destroys the bond between the coffin bone and hoof wall. The tope of the coffin bone is anchored by its articulations with the second pastern bone and the deep flexor tendon exerts a constant backward pull on the coffin bone, which made it rotate down and back when the laminar bond between the bond and the hoof wall is destroyed by a founder incident.
The most common cause of laminitis is grass or pasture founder. It can be a sudden happening or it can come on over a period of weeks. It occurs in lots of hunting horses that are turned out to pasture in the off season. Most horses that have this problem are easy keepers. They tend to get fat just looking at feed and most have a big cresty neck. Green grass has estrogen, which causes fat deposits and adds to the problem by increasing body weight and causing histamine release resulting in laminitis. The typical picture is a big, fat, cresty horse with the hind legs tucked under to get the weight off the front feet. Most of the body weight is in front, so when the horse tries to move one foot the other hurts so bad he give the appearance of walking on eggs. The legs are not involved except that the flexor tendon sometimes can fatigue and may have some swelling.
Acute or sudden cases of founder, where there is a specific incident or just a sudden severe lameness, are emergency situations. Veterinary attention is necessary. If treatment can decrease the reaction in the foot to save the lamina, it may mean the difference between having a salvageable horse or one requiring euthanasia.
The more chronic or insidious pasture founder cases probably are not emergencies, but many of them require x-rays to determine coffin bone rotation and follow-up care with a horseshoer who understands the problem and who is up-to-date on proper trimming and shoeing techniques for laminitis.
Many foundered horses can be managed so they can again become useful, but many also end up chronically lame and some are affected to the degree they must be humanely destroyed.
Some of those big, fat, easy keepers, just cannot be on pasture. Some will founder just eating the weeds and grass they can reach through the corral fences. The other thing to remember is - all things in moderation. Too much grain is not good. Oats are the best when feeding grain. If a horse is hot, cool him out and water him gradually. Horse sense "should prevail". Just think of your horse before you think of yourself.
We would like to take this opportunity to thank HARRIS VETERINARY CLINIC, in Grand Junction, Colorado for providing us with this information.
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