Older Horses Part 4: Hoof and Joint Care
Routine hoof care is critical for your horse’s soundness and well-being. “A lot of times, when horses are on pasture, not in performance and not getting ridden very often, hoof problems arise due to longer intervals between care,” Tanner says. Whether a horse is barefoot or shod, “routine trimming by a skilled farrier,” is essential to reduce the possibility of laminitis, he adds.
Photo: Anne M. Eberhardt/The Horse
The aging process brings with it some inevitable changes in horses. As is often the case with humans, the horse's joints begin to "stiffen" as he gets older. Eventually, many horses are unable to meet the same performance standards that they did when younger, and we begin to wonder what we can do to help.
There are a great many horses that fit into this category. Some veterinarians have estimated that about 20% of the horse population is older than 15 years of age. It is believed that one year of a horse's life is equal to an average of three years of a human life. This would mean that a 15-year-old horse could be compared to a 45-year-old person.
In both cases, individuals of that age can remain healthy and lead useful lives, but issues like proper nutrition and attention to the joints are required when such needs surface. In some cases joint supplements might be called for, and if that doesn't get the job done, joint injection might be a treatment of choice. We'll concentrate on supplements in this article on older horses, leaving a discussion of joint injections for the actively competing horse.
One of the problems we face with our equine companions is that there are a lot of joints to deal with, and they have been subjected to a variety of stresses and pressures during the horse's lifetime of activity. These sometimes fragile joints have been given the task of absorbing shock, allowing for nearly frictionless movement and bearing the weight of a body that often is in the 1,200-pound to 1,500-pound range.
It is a given that the more arduous the activity, the more stress and pressure on the joints.
If the horse is gifted with good conformation, it often has been able to handle these stresses and still remain sound and strong. However, if the reverse is true, the wear and tear on joints has been exacerbated. The problem is further complicated by the fact that there are 205 bones in the horse's skeleton. Twenty of these bones are in each foreleg and 20 in each rear leg, for a grand total of 80 bones in the four equine legs. Each is connected or aligned with one or more other bones, allowing the horse to lift, bend, and flex its legs. This ability permits the horse to travel across the ground, absorbing concussion along the way.
The part of the horse's anatomy to strike the ground first in a given stride is the hoof. It starts the concussion absorption process while, at the same time, protecting the inner bones, joints, blood vessels, and nerves of the foot. Generally speaking, as a horse ages its hoof remains strong if it was properly conformed at birth and well-cared-for during the horse's lifetime.
The problem with hooves, more often than not as the horse ages, involves the care, or lack of it, that they receive. Often one of the first aspects of good care that is neglected when a horse reaches its retirement years is its feet. It is important to remember that a horse requires ongoing hoof care even when it is no longer working on a daily basis.
Some older horses might require regular shoeing as protection for the foot or to relieve pressure on soft tissues; many do better being barefoot.
However, the aging process will very likely take a heavier toll on the joints than on the feet. We'll launch this discussion on joints of the older horse with a brief review of material presented here in the past and with information taken from presentations by a variety of experts in the field.
Types of Joints
The spot where one bone joins another is the joint, and there are three basic types. They are:
Synovial joints These are the movable joints and the ones that tend to be at risk during the aging process. An example of a synovial joint is the knee, which actually contains three joints and multiple bones. In a manner of speaking the synovial joints are the horse's ball bearings. A synovial joint consists of two or more bone ends covered by articular cartilage. The cartilage within the joint is smooth and resilient, allowing for nearly frictionless movement. Each joint capsule also contains an inner lining called the synovial membrane, which secretes synovial fluid to lubricate the joints.
Cartilaginous joints These joints are slightly movable or immovable, depending on the bones involved. Cartilaginous joints are united by fibrocartilage, hyaline cartilage, or both. The connective tissues between vertebrae comprise a cartilaginous joint.
Fibrous joints These basically are immovable joints where the bones are bound by fibrous tissue that ossifies as the horse matures. An example is joints within the equine skull.
We must point out that most of the problems that develop in the joints of older horses involve synovial joints. The reason is quite obvious: They are the ones that sustain the most friction and stress and are called upon to absorb the most concussion.
Not all horses are born equal in joint structure, and not all suffer the same negative effects of aging. Each must be treated as an individual and, generally speaking, the advice and help of a veterinarian is required to help guide the average owner along the pathways of proper care and treatment when something goes wrong. The joints of some horses are so strong and healthy that they are capable of jumping, dressage, and other strenuous activities well into their 20s and beyond. Other horses will show signs of stiffness much earlier, compelling the handler to reduce stressful activity at a much earlier age and, perhaps, seek professional help to determine whether something more is needed.
One of the suggestions a veterinarian might proffer for the older horse with joint problems is a supplement, says Jeremy D. Hubert, BVSc, MRCVS, Dipl. ACVS, assistant professor in equine surgery at Louisiana State University. Some of the information he has presented publicly can be found at www.lsuequine.com. Information from Hubert for this article has been taken from his articles and from a personal interview.
It is difficult, he says, for the average horse owner to find his or her way through the maze of information and advertising concerning joint supplements and joint injection. Just what approach might be suggested, he says, will vary practitioner to practitioner and from case to case.
Most joint supplements, Hubert says, involve combinations of several substances, all of which are designed to assist in slowing joint degradation.
He describes joint degradation thusly: "Joint degradation refers to the inflammatory changes that occur and resultant breakdown of the articular cartilage in a joint and the subsequent changes that lead to development and progression of arthritis. By definition, arthritis simply means inflammation of a joint."
Inflammation leads to the breakdown of articular cartilage in the joint (usually associated with inflammation) that leads to development or progression of arthritis, notes Wayne McIlwraith, BVSc, PhD, FRCVS, DSc, DrMed Vet (hc), Dipl. ACVS, Barbara Cox Anthony Chair and director of Orthopedic Research at Colorado State University.
"Inflammation of the synovial membrane and joint capsule is common with athletic horses with repeated trauma," says McIlwraith. "This inflammtion leads to an inflammatory cascade, which in turn leads to further damage to the cartilage matrix."
Hubert adds, "Ultimately, (this cascade) changes the cartilage with respect to its ability to (handle) its normal functions," he continues. "The (clinical) changes noticed early may be as simple as just a warm joint with mild effusion (increased amount of joint fluid). If the joint is not rested and the cycle of inflammation is not broken or stopped, then continued damage can occur. This could result in a thinning of the cartilage; thus its ability to resist concussive forces becomes diminished. At this point there is the potential that the bone directly beneath the cartilage (subchondral bone) can become damaged. Bony changes may start as the bone becomes remodeled in response to trauma or concussion that is not absorbed by normal healthy cartilage."
"The term osteoarthritis is generally used for progressive degradation of the cartilage, which is an irreversible condition," notes McIlwraith. "These degenerative changes are accompanied by inflammation, but the process becomes more chronic. The term degenerative joint disease (DJD) is used interchangeably with osteoarthritis (OA)."
When Supplements Are Useful
There are three basic scenarios where joint supplements might be helpful for treating joint disease, Hubert believes. They include:
- The older arthritic horse.
- The horse convalescing from an orthopedic injury.
- The hard-working, competing horse with no sign of joint injury.
While there are a myriad of different commercially available products that supporters claim will prevent and resolve joint problems and injuries, there is limited scientific data in horses to support their efficacy, notes McIlwraith. "However, the two most common ingredients used are glucosamine and chondroitin sulfate."
Here, in abbreviated form, is how the products can be described.
Glucosamine This is a type of sugar that is found concentrated in joint cartilage. It acts as a precursor for the building block units found within articular cartilage. These building blocks have special biomolecular properties that enable the cartilage to absorb large quantities of water, giving it a spongelike characteristic. Glucosamine is a small water-soluble molecule that is absorbed easily if taken orally and has been shown to be nontoxic. Cartilage cells themselves synthesize gluocosamine from glucose, but when available, glucosamine is preferred over glucose as a food source. When administered orally, glucosamine hydrochloride yields greater quantities of the active form of glucosamine than glucosamine sulfate. It is the active form of glucosamine that directly determines how readily the glucosamine supplement is made available to the body.
The question before the house when a discussion of supplements arises often involves the amount of the supplement that actually goes through the digestive process and winds up in the joints to carry out its therapeutic work. With glucosamine hydrochloride, this might not be a problem in the horse, providing that it works as it has in experiments involving rats, dogs, and humans. In those experiments, according to Hubert, 95% of orally administered glucosamine hydrochloride was absorbed and made available to the body for use by the articular cartilage. (Other studies have shown that the compound's bioavailability in the horse is only about 5.9%.)
Hubert says if your average 1,000-pound horse has an oral intake of 10,000 mg of glucosamine hydrochloride on a daily basis, it will slow down the degeneration of cartilage and even help repair in conjunction with other traditional therapies. Glucosamine has been shown to have anti-inflammatory effects as well as being a precursor molecule for the cartilage matrix."
Other veterinarians take a more cautious approach and say the efficacy of glucosamine hydrochloride is largely unsubstantiated. Scientific studies on glucosamine question significant absorption in the horse, notes McIlwraith. But there appear to be no negative side effects when using this medication, therefore there isn't a strong reason to avoid them. Antonio Cruz, DVM, MVM, MSc, DrMedVet, Dipl. ACVS, ECVS, associate professor of large animal surgery in the Comparative Orthopaedics Research Laboratory at the University of Guelph's Ontario Veterinary College, says, "It (the decision to use joint supplements) is a hard issue, and one that polarizes people. Bottom line is that it is a largely unregulated industry and there is no good scientific evidence of treatment efficacy ... but lots of people are making lots of money."
Chondroitin sulfate (CS) Hubert says this is the predominant glycosaminoglycan found in adult articular cartilage. In vitro (in the lab) studies have demonstrated it is effective in inhibiting the enzymes associated with inflammation and tissue destruction. However, Hubert adds, there is a downside, as studies also have shown that the absorption of CS has been only in the 15% range for man, dogs, and rats.
Studies of absorption in the horse support absorption of chondroitin sulfate, at least the lower molecular weight form that is a component of Cosequin, says McIlwraith.
In addition to glucosamine and chondroitin sulfate products, neutraceuticals containing omega-3 fatty acids and avocado/ soy combinations have been developed. The latter combination has recently been shown in a controlled study at Colorado State University to have chondroprotective effects in osteoarthritis, with decreased amounts of articular cartilage degredation in the horse, says McIlwraith.
That raises the question of whether adding vitamin and mineral supplements will improve joint problems. If the horse is on a balanced diet, Hubert says, adding vitamins and minerals might be unnecessary.
The take-home message appears to be that if a horse does develop joint problems in its senior years, the first steps taken should be to ensure that it is on an appropriate diet and that it can masticate (chew) and digest the food ingested. It should also be involved in an appropriate regimen of exercise and rest. If additional relief from arthritis is required, the use of an oral supplement might be beneficial, but there is still a need for more scientific validation of these types of products.
About the Author
Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.
POLL: Rehabbing the Injured Horse