Your Senior Horse – She Ain’t What She Used To Be
Dr. Phillip Johnson
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. A thick coat that doesn't shed out ("hirsutism")
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.
When Is a Horse Considered Old?
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 would 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.
When Is a Problem Life-Threatening?
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.
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 and 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 6 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:
Progressive weight loss
Excessive drinking and urinating
Sweating and unusual dampness of the coat
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 causes pain and interferes 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 expensive, to treatment locally with cryotherapy, surgery, and/or local injection of chemotherapeutic agents. Most of the time, however, cancer is a serious life-threatening disease in horses 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.