Thanks to better nutrition, better veterinary care and perseverance on the part of owners who love their long-time companions, the health and athletic ability of older horses is much better today. If you want to optimize your horse's health as s/he ages, it is first important to know the problems that arise. The earlier you react to these issues, the more successful will be the outcome.
However, some problems are not treatable, and this can be a painful realization if it is sudden. So take a minute to familiarize yourself with the problems that are likely to develop with age, and understand a bit about those symptoms that are serious and possibly untreatable. This will prepare you to provide the best quality of life for your horse until the end.
Appearance of Old Age
Like people, some horses age at different rates than others. The appearance of old age could come as early as 15 to 20 years in some horses or as late as 20 to 35 years in others. Generally, however, most people regard horses as being relatively old after 20 years of age, when old age problems start to become prevalent. Twenty years in a horse corresponds to approximately 50 to 60 human years and 30 years would be around 80 to 90 human years. These estimates are based on the maximum expected longevity of the horse, which is thought to be 44 years.
Accounts of horses over 44 years have been difficult to verify. The average horse is healthier later in life, but the actual life span has probably not changed, and horses reaching their 30s and 40s are still rare. The actual life span may be difficult to improve because of the combination of problems that develop, and for now, the lack of resources to solve all of them, especially when multiple problems exist.
If there are problems that result in a significant loss of function of any body system, cause persistent pain that cannot be easily controlled, and/or there is a lack of response to aggressive treatment, the problem could be life-threatening. These issues involve quality of life, and you should discuss them with your veterinarian, family and friends.
Although it's hard to talk about your horse getting "old", it's going to happen. Every horse is different in the way he reacts and expresses pain and loss of function, so each horse has to be evaluated as an individual. A thorough evaluation should be performed, and if there is any question, you should work with your veterinarian to make your horse as comfortable as possible, yet decide what is reasonable to assure a good quality of life.
Dental problems often cause persistent pain and loss of function such as chewing difficulties and poor digestion. The horse's cheek teeth are continuously growing but at the same time they're being worn down by the action of chewing. This is one reason that horses can no longer cope in nature. As the cheek teeth wear down there is increased risk for other tooth problems such as tooth root abscesses, periodontal (soft tissue) disease and sinusitis, that can be very painful.
Dental care is important for aging horses, and you can reduce the risk of health problems due to dental disease with routine dental care and switching to a diet that does not require a significant amount of grinding action. Still, however, horses without teeth, even when fed purees, mashed carrots and tonics, have problems maintaining their body weight, and once they are drained of body fat and show the ribs, the process can be very difficult to reverse.
Horses that have lost weight to the point where their ribs or back are prominent, will take at least six months under ideal circumstances to return to weight on full feed. This can be extremely difficult to achieve without good teeth. In general, horses with serious lack of teeth that lose weight despite your best efforts to feed them, may have difficulty surviving any change in environment, stresses, or new demands.
Equine Cushing's Disease (ECD)
Cushing's disease causes loss of function of the hormonal system and may not respond to treatment. Many older horses develop ECD, which is caused by a growth on the pituitary gland located at the base of the brain. This very active growth releases a hormone that causes the adrenal gland to be hyperactive and to produce excessive amounts of steroid hormones. The resulting symptoms include:
This condition also leads to reduced ability to fight infections, so older horses with ECD are prone to infectious diseases such as EPM, tooth root infections, sinusitis and common respiratory infections. There are special tests to support the diagnosis and specific treatments, so it is well worth having a workup for this problem. If untreated, horses with ECD get progressively thinner, dehydrate, founder or suffer chronic infections that don't respond well to antibiotics.
In general, it is the complexity of secondary problems that may become untreatable. For example, severe laminitis, pneumonia or severe sinusitis, which cause pain and interfere with breathing and eating, are serious and possibly irreversible. Weight loss may also be too rapid to reverse. In some horses, the pituitary gets so large it actually puts pressure on the hypothalamus, that part of the brain that regulates "flight or fight" responses, emotions, thermoregulation and other hormonal functions. The horse cannot maintain his body temperature or he has seizures.
Failure of The Immune System
One reason old horses do not respond to conventional treatments is failure of the immune system brought about by old age. Treatment of infections in older horses must be aggressive and often requires a combination of antibiotics, which can be expensive. While it's always worth treating an infection, a lack of response is a cardinal sign that the "back-stop" function of the immune system is failing.
Like people, older horses are prone cancer, which causes pain, loss of function and lack of response to conventional treatments. Old gray horses invariably develop melanoma of the skin. Other common cancers include lymphosarcoma, squamous cell carcinoma ("cancer eye"), and fibrosarcomas. At the present time, there are not many options for treating cancers in horses, since radiation and chemotherapy are extremely expensive or not feasible because of the size of the animals.
If the cancer is localized to one area, there are possibilities, although they may be expensive, of local treatment with cryotherapy, surgery, and/or local injection of chemotherapeutic agents. Most of the time, however, cancer is a life-threatening disease without many options. Tumors often cause extensive local damage making organs dysfunctional such as the loss of swallowing ability (mouth, tongue and esophageal tumors), interference with breathing (nasal, tracheal or lung tumors), digestion (intestinal tumors), urination (bladder, genital tumors), defecation (melanomas of the tail), or even walking (spinal tumors). If any of these areas are affected to the point where the horse is in constant pain, experiences serious weight loss or organ system failure, the condition may not be treatable.
Inefficient Intestinal System
Along with the relative decrease in the effectiveness of the aged horse's cheek teeth, the intestines of older horses appears to be less efficient at digesting their food. This is why some horses appear to be dropping weight slowly, despite feeding them more. Before assuming this is the problem, the intestinal absorption of the horse should be tested, and a complete blood chemistry panel and hormone analysis performed.
The problem of age-related poor intestinal digestion may not be hopeless, in that diets higher in proteins and calories can offset the eventual progression of weight loss. If there are other coexisting causes of weight loss (e.g. dental disease or kidney failure), this can be serious, because you just will not be able to get enough food into the horse to keep up. If despite your efforts to push the feed, the horse continues to lose weight, this could become very serious once the horse is ribby, especially for maintaining body temperature in the winter, and fighting off any stresses or infections that are encountered from time to time.
Arthritis and Navicular Disease
Pain and function (mobility) are the big issues that determine quality of life. Although certain joints sustain the greatest wear and tear throughout the life of a horse, it is not always these "obvious" sore joints that act up later in life.
Horses with arthritis are generally stiff, especially in the morning after they have lain motionless for a period of time. The problem gets even worse in cold or wet weather. The stiffness worsens over time, and eventually the horse is so painful that he doesn't want to move, and may even groan. Arthritis in the legs is more obvious, in that the horse's mobility has declined, and there is a progressive "crouching" stance or actual limping. However, neck arthritis can also be a big problem, although more subtle. In this case, the horse exhibits difficulty reaching the ground. Pain and loss of function (immobility) add up in the arthritic horse.
There are many options for treating arthritis. For the horse with single joint problems that can be pinpointed, local treatments are available. However, most old horses have multiple joints with arthritis all at once, often in inaccessible regions such as the hip, or neck.
The best option is the judicious use of pain killers or anti-inflammatories. Examples include phenylbutazone, Banamine® (flunixin meglumine) and ketoprofen. Eventually it becomes difficult to get enough of these painkillers into the horse without causing side effects, including loss of appetite, gastric ulcers, weight loss and diarrhea. You should talk to your veterinarian about a schedule of treatments to soften that possibility. Cartilage protective agents should also be considered at this point, for example chondroitin sulfate and polysulfated glucosaminoglycans (PSGAGs), which are available as supplements or injections.
This causes obvious signs of heel pain, and is easily managed early in life with corrective shoeing and oral medications, or in some cases, by surgery ("neurectomy"). The choice to perform neurectomy (to "nerve") an old horse depends on what other problems exist, and must not be done without serious consideration of potential complications.
Orthopedic (arthritis, navicular) problems are untreatable:
Economics obviously plays a role here as well, since anti-inflammatory and cartilage protective agents, if used, can be expensive. Determining when arthritis is a consideration for euthanasia is most difficult, because the problems are long-standing, so get another opinion and step back.
Heart Valve Disease
Heart murmurs are a dime a dozen in old horses, but they are mostly benign. However, with the procession of years, the heart valves start to "wear out." The valves most commonly affected include the aortic and mitral valves, because they are under the most stress. They function to control blood flow through and out of the left ventricle, the part of the heart that pumps blood to every place in the body except the lungs.
When these valves become leaky, you can see back flow of blood within the heart on ultrasound, which ultimately causes the heart to fail due to inadequate delivery of blood, and therefore oxygen, to tissues. This is one reason that it is common to detect heart murmurs in old horses, although many are inconsequential and do not require further attention.
An ultrasound examination ("echocardiogram") provides information that will forewarn you if the murmur is serious. If a loud murmur should arise, it should be checked then rechecked at no more than 6 month intervals. If it gets louder or there are signs of poor heart function (poor pulses, lethargy, dark mucous membranes, increasing breathing rate), it should be treated. If the heart is rechecked by ultrasound, the cardiologist can see how fast the problem is progressing, and help you prepare for a downturn in quality of life if that seems imminent.
Symptoms of heart failure include: a horse with a loud murmur that is lethargic, dropping weight, reluctant to move, stocking up, accumulating edema on the belly, disinterested in food, exhibiting frequent restlessness. Also, poor pulses, visible pulses in the neck, bluish or dark mucous membranes, increased breathing effort, or froth from the nostrils are present. These symptoms need to be addressed right away, and may be treatable for a period of time, usually no more than a few days to weeks.
Kidney failure is a problem that most horses face if they live long enough, and it is a major cause of unexplained weight loss. The disease can be recognized by the following symptoms:
A urinalysis, ultrasound of the kidney and perhaps a biopsy should be pursued to evaluate the extent of the problem. As you can see, there are many causes of weight loss in the older horse, so a thorough evaluation is necessary in every case.
"Broken wind, COPD" is extremely common in the older horse. Up to 20 percent of horses get heaves, and it can be highly debilitating and even cause sudden death. Fortunately, there are great options for the horse today, including hypo-allergenic hay, pelleted feeds to replace hay (since these horses are ultra-sensitive to mold found in hay), and oral and inhaled medications. If the environment can be managed diligently, and the horse put on medications without side effects, horses rarely die from heaves today. They may, on the other hand, not be used for riding.
One company, Trudell Medical International (London, Ontario) makes an inhaler for horses that allows delivery of steroids or bronchodilators directly to the lung, allowing for control of the disease for years, without side effects. The steroid keeps the airway inflammation (the basis for heaves) in check, and prevents attacks. The bronchodilator markedly reduces the work of breathing. Clenbuterol is an oral bronchodilator that reduces the symptoms of heaves in a high a percentage of cases.
Without any treatment, the breathing problems in these horses worsen, and they can die from either this problem or heart failure. Make certain they are not exposed to hay; if you are diligent, it's possible for them to live a long happy life without attacks of heaves. In some cases, however, even the most diligent environmental management does not prevent heaves, because there are so many things in the environment that cause it.
Horses with heaves that do not respond to medications and being taken off hay, have constant difficult breathing (increased abdominal effort, nasal flaring), are weak, or have progressive weight loss, are candidates for euthanasia.
Of note, unlike people, horses do not appear to be affected by hardening of the arteries, heart attack (MI), stroke, senile dementia or Alzheimer's disease.