by Lydia Miller, DVM, AAEP, Jill Beech, DVM, Dipl. ACVIM
Fortunately for our nation’s horse population, interest in equine geriatrics among veterinarians and researchers has been increasing. As a result, it has been found that not only do senior horses have different preventive care needs, but also that certain disease conditions become more common as horses age. Many of the conditions we associate with “old age” in the horse–like lameness, weight loss, or poor shedding–actually might be preventable or treatable.
Normal “wear and tear” plus any of these practices — long years of an irregular exercise program, poor riding, poor footing, and poor foot care — can set a horse up for lameness. One common cause of lameness in the senior horse, degenerative joint disease (DJD) or arthritis, may cause pain which not only affects the horse’s gait, but also makes proper foot care difficult. If a horse is unable to stand comfortably or bend its legs for hoof trimming or shoeing, inadequate foot care can result, making the original lameness worse. Some senior horses require pain-killers (analgesics) before their farrier’s appointment to make the procedure easier. Also, owners must remember that just because a horse is not being ridden, his or her feet cannot be ignored; they still require regular attention and trimming.
Horses experiencing pain from DJD may require analgesics, but treatment should be under the advice of a veterinarian. Various different non-steroidal medications may be used (most commonly phenylbutazone), but these may have serious side effects when given at high doses and/or over a long period of time. Stomach and colon ulcers as well as kidney damage are potential side effects that can be fatal. Various other substances have been professed to benefit horses with arthritis, but there is little scientific proof of their effectiveness. Acupuncture is also used with anecdotal reports of success. Older horses with endocrine disorders and altered immune function appear prone to laminitis and foot abscesses. These conditions especially require the combined expertise and skills of a veterinarian and a farrier.
Owners of older horses might find that it is becoming harder and harder for their horse to maintain their weight. Although this condition can have many causes, inadequate nutrition and poor teeth are probably the most common. In general, as horses become aged, they require foodstuffs that are calorie-rich, easily chewed and digested, and contain additional vitamins. Their mineral intake should be balanced. As horses’ teeth grow out with age, they can become loose or diseased, making effective chewing not only impossible, but painful. Tooth root abscess, which can lead to sinus infections, can produce a foul odor from the horse’s mouth or nostrils. If this occurs, a veterinarian should be contacted. After about the age of 15 years, most horses should have their teeth checked by a veterinarian at least every six months to help prevent such conditions. Also, just because a horse is advanced in years doesn’t mean he or she shouldn’t still be part of a well-rounded deworming program.
Although aged horses tend to develop adenomas (benign tumors) of the thyroid gland, these are nearly always nonfunctional, requiring no attention unless their size causes problems, such as with swallowing. Probably the most common endocrine disorder affecting the senior horse is hyperplasia (increased cell growth) of the pituitary gland, often referred to as a pituitary tumor or “Cushing’s Disease.” Despite the fact that not every horse with this condition will exhibit the “classic” signs of the disease, certain changes are considered to be hallmarks:
- hirsutism (excessive long, curly hair), delayed shedding/failure to shed the winter hair coat
- muscle wasting
- a "pot belly"
- cresty neck
- puffiness above the eyes
- laminitis or founder
- increased susceptibility to infections
The "classic" case probably does not require testing to confirm pituitary dysfunction, but the less obvious cases do. Various blood tests may be performed but one-time, baseline measurements are often not very useful in the diagnosis of this disease unless a value is extremely elevated or more than one value is abnormal. For example, consistently high blood sugar along with hallmark signs of the disease may be enough evidence to begin treatment. In other cases, a dexamethasone suppression test — where the horse’s natural steroid level is measured before and after giving this man-made steroid — may be a more useful indicator of pituitary function.
As horses age, other diseases and conditions become more common. Neoplasia or various types of cancer can affect older horses. Clinical signs, diagnosis and treatment depend upon the organ affected. Unless there is one, single, accessible tumor that can be removed, there might not be an effective treatment.
Senior horses also are more prone to certain types of colic than young horses. Obviously, poorly chewed food can be a problem. Lipomas tend to occur in middle-aged and older horses and can strangulate intestine, requiring surgery.
As horses age, they often develop cataracts and/or floating material in the fluid of the eye. Although these can result in impaired vision, horses seem to function quite well even with major changes in their eyes.
Although there are other conditions that affect the older horse, this overview covers the more common ones. Good, consistent care and an appropriate preventive health care program can do a great deal toward maintaining the well-being of our aged equine companions.
Lydia Miller, DVM, in conjunction with Jill Beech, DVM, Dipl. ACVIM, New Bolton Center, University of Pennsylvania College of Veterinary Medicine and AAEP member.
American Association of Equine Practitioners
4075 Iron Works Pike
Lexington, KY 40511