Published 8/93
Sarah L. Ralston, VMD, Ph.D., ACVN, Extension Specialist in Equine Nutrition Science
When Does an Old Horse Require Special Care?
As with humans, chronological age does not always match the aging process. By American Quarter Horse Association standards, a horse over 16 years old is “aged.” In studies by the author (Ralston, 1988, 1989) over 70% of horses over 20 years old had conditions which required special care though many were still serviceably sound. Indeed, many of these horses were still rideable or, in the case of stallions and mares, used for breeding. Age alone should not be a criterion for retirement or special management. However, if an aged horse has one or more of the problems in Table 1, it is a candidate for special care.
Management of Changes and Problems Associated with Aging in Horses
Arthritis
As with human athletes, years of stress, injuries, and general wear and tear can result in painful and crippling arthritic changes in the limbs of horses. Arthritis is a combination of inflammation and degeneration of the tissues associated with a joint which reduce the ability to flex or bear weight on the joint. Ringbone and spavin are examples of arthritic problems commonly seen in older horses. However, a little stiffness that the aged horse will warm out of fairly quickly should not be a cause for alarm or retirement.
To make the arthritic horse more comfortable, consult with your farrier and veterinarian regarding the optimal way to shoe or trim the horse. Keep the horse on soft footing or bedding (not too deep, it’s harder to move around in). Use anti-inflammatory drugs recommended by your veterinarian if the horse is in chronic pain. Don’t let the horse become obese, since extra weight will increase the stress on its legs.
Do not confine the horse to a stall unless absolutely necessary for medical reasons—if it can move about it will be less stiff. Ideally there should be free access to turnout, preferably with another compatible horse for company.
Weight Loss/Poor Condition
The most common causes of weight loss in aged horses are failure to keep up with deworming schedules, debilitating diseases, and/or poor dentition. However, an aged horse not suffering from any of these problems still may benefit from a change in diet. (Ralston et al., 1989) reported that horses over 20 years old had reduced digestion of fiber, protein, and phosphorous relative to young horses fed the same diet though many of the aged horses were still able to maintain good body condition on good quality hay rations. Malabsorption of nutrients in aged horses may be the consequence of chronic parasitic damage to the intestines or alterations in the digestive processes.
The diet of horses over 20 years old should have at least 12% protein and 0.3% phosphorus with calcium equal to or greater than the phosphorus content but less than 1% on a dry matter basis (Ralston, 1989). Digestibility of the concentrates should be maximized by processing (extrusion or pelleting). A typical ration might consist of top quality hay (preferably a grass/alfalfa mix unless there are kidney or liver problems—see below), highly digestible pellets or extruded feeds designed for weanlings or geriatric horses, plus the usual free choice water and salt. Soybean meal is an excellent protein supplement for the aged horse.
Older horses are more sensitive to severe weather, be it heat or cold. It is essential that adequate shelter be provided and that the higher energy needs in winter are met by providing increased feed in a more highly digestible form, such as pelleted or extruded feeds. Constipation/ impaction problems can be reduced by insuring free access to clean, fresh, unfrozen water in the winter. If the horse does not drink well, feeding water soaked feeds or mashes (at least 2 gallons of water per feeding) will help increase fluid intake. Addition of 1 to 2 ounces of salt to the feed may also encourage increased water intake but should be done only if the horse has unlimited access to water.
Inadequate Dentition/Tooth Loss
All horses require regular tooth care. Horse’s teeth grow continuously throughout their lives and frequently form sharp points on the outside of the upper molars and inside of the lower molars. These points make it painful to chew and cause the horse to dribble feed or partially chewed boluses of hay from its mouth (“quidding”). The teeth of horses fed dry hay and grain need more frequent attention than those on lush pasture. Tooth loss, especially molars or premolars, also reduces the ability to adequately prehend and chew feed. If an upper molar is lost, the opposing teeth will grow down into the space (wave mouth), making it difficult to chew. Inadequate dentition predisposes the horse to weight loss and/or choke.
Older horses, especially those known to have missing molars, should have their teeth checked at least twice a year. If chewing is difficult, “soups” of pelleted feeds may be fed. Only “complete” pelleted feeds which are designed to be fed without hay should be used since many pelleted feeds are only grain substitutes and do not contain the proper mineral balance to be used as the major or sole source of nutrition for the horse. Enough water should be added to the pellets to make a soupy consistency (at least 1/2 gallon of water per lb feed) to prevent choke. Hay can still be fed if choke is not a problem, even if most of it is wasted. Access to good pasture is desirable.
However, if front incisors are missing (as in cribbers) or badly aligned, do not rely on pasture for nutrition. These horses must be fed complete feeds or loose hay and/or hay cubes since they can not graze effectively.
Pituitary/Thyroid Tumors
In a study of geriatric horses (Ralston et al., 1989), over 70% of the horses over the age of 20 had at least subclinical signs (altered glucose and cortisol metabolism) of pituitary/thyroid tumors. Mares appeared to be predisposed to pituitary tumors whereas thyroid tumors were more common in geldings. Thyroid tumors usually are considered to be benign but can increase the incidence of obesity and founder. Old mares with pituitary tumors, even in the early pre-clinical stages, had lower blood vitamin C than did unaffected or younger mares. This may explain in part the increased susceptibility to viral infections. Both types of tumor cause relative glucose intolerance, in which the horse becomes less sensitive to the action of insulin. After a high sugar or starch meal (such as sweet feed or processed grains) blood levels of both glucose and insulin become abnormally high, resulting in increased thirst and urination. Studies by the author have shown that pelleted or extruded feeds, especially those formulated to be “complete,” result in more moderate glucose and insulin responses after feeding and may help control this problem (Ralston, unpublished data).
Treatment is available for thyroid tumors. The horse may be placed on thyroid hormone replacement therapy if shown to be hypothyroid through blood tests. Pharmacologic treatment for pituitary tumors is experimental at this time.
Due to the liability risks of extralabel drug use and expense of pharmacologic treatment, most veterinarians elect to treat only the clinical symptoms of pituitary tumors. If properly managed, horses with these tumors can live for years after appearance of the clinical signs.
Management of the clinical problems associated with tumors is fairly easy. It is essential that all older horses be maintained on regular vaccination and deworming schedules. Since plasma levels of vitamin C are reduced in aged horses with pituitary tumors, 5 to 10 gm of ascorbic acid in the feed per day may be beneficial. If water intake and urine output are increased, fresh, clean water should be available free choice. If chronic founder is a problem, the horse’s access to fresh grass and grain must be restricted and sudden dietary changes avoided at all costs. The thick hair coat should be clipped in the summer, in addition to providing shelter from the sun to keep the horse comfortable on hot summer days.
Altered Kidney/Liver Function
Chronic kidney or liver failure is not as common in aged horses as it is in cats and dogs, but still can occur. The degeneration of the kidney and liver ability to function is progressive and irreversible but can be slowed and the clinical signs managed to a degree with diet.
Reduced kidney function will result in renal stones (calculi), bladder stones, weight loss, loss of appetite, and potentially death. Horses are unique in that they excrete excess dietary calcium through their urine instead of their feces as do other animals. As a result, if kidney function is reduced, renal and bladder “stones” of calcium oxalate are more likely to occur as well as an increase (potentially lethal) in blood calcium. Horses with kidney failure should be put on low calcium diets (<0.45% calcium on a dry matter basis). Based on data from other species, protein and phosphorus also should be restricted to less than 10% and 0.30% respectively. Good quality grass hay and corn or a complete pelleted ration for mature horses (10% protein) are the feeds of choice. Avoid legumes (alfalfa and clover), wheat bran, and beet pulp due to high calcium (legumes, beet pulp) or phosphorus (wheat bran) content.
Liver failure results in weight loss, lethargy, jaundice (yellow mucous membranes and sclera [whites of the eyes]), loss of appetite, and intolerance of fat and protein in the diet. If severe, the horse may show behavioral changes such as irritability, aimless wandering or circling, or pressing its head against objects. Affected horses require increased sugar sources to maintain their blood glucose levels and are intolerant of high protein or fat in the diet. Legumes should not be fed due to the high protein content. The diet should emphasize starch intake (grains or concentrates) though fiber sources (hay, beet pulp) are still necessary to avoid gastrointestinal dysfunction. Grass hay, low protein sweet feeds, corn, and milo are recommended components of the ration. Wheat bran and beet pulp are acceptable supplements in these cases. Since the liver is the site of B-vitamin (especially niacin) and vitamin C synthesis in the horse, daily oral supplementation with B-complex and ascorbic acid may be beneficial.
Summary
A horse should not be treated differently just because it has reached a certain chronological age. However, if problems related to aging are present, changes in management and medications may be needed to keep the older horse comfortable. Aged horses that do not have reduced kidney or liver function will benefit from a diet more similar to that recommended for weanlings than that for normal adult maintenance. Calcium and protein, however, will need to be restricted if the horse has kidney failure.
Teeth should be checked every 6 months, or even more frequently if premolars or molars are missing. If teeth are a problem, soups can be made out of complete pelleted feed. Vaccinations and deworming schedules should be carefully maintained.
Pituitary and thyroid tumors are very common in aged horses. Late signs are failure to shed out in the summer, increased drinking and urination, and chronic founder. There are pharmacologic treatments that can help, but the best one is expensive and is not currently approved for use in horses.
Adequate shelter is a must for older horses, especially in the winter. However confining a slightly arthritic horse to a stall is not doing it any favors. A well-built run-in shed and heavy blanket would be better in most cases.
Table 1: Conditions requiring special attention in aged horses. See text for more details.
|
Condition |
Clinical Signs |
Management Considerations |
|
Arthritis |
Chronic lameness Bone deformity around joints Inflexible joints |
Shoeing/trimming Bedding Avoid obesity Anti-inflammatory therapy |
|
Weight loss |
Inability to maintain good body condition despite good teeth, and a ration that is adequate for mature horses. |
Teeth Diet* Shelter Deworming Liver or kidney failure Tumors Malabsorption |
|
Inadequate dentition |
Sharp points on molars Loss of teeth Inability to chew feed “Quidding” of hay |
Regular tooth care Diet* |
|
Pituitary/thyroid tumors |
Failure to shed winter coat in the summer Recurrent viral infections Chronic founder (laminitis) Increased water intake and urination Excessive weight loss (pituitary tumors) or gain (thyroid tumors) |
Grooming Diet* Vaccination Water access |
|
Kidney/liver failure |
Weight loss Lethargy Poor appetite Difficult or frequent urination (kidney) |
Diet* Supplements |
|
Grey hair appearing around ears, eyes and forehead |
This is not a problem, merely a sign of aging |
*See Diet Recommendations in Table 2.
Table 2: Dietary management of conditions associated with aging in horses
|
Condition |
Recommended Diet Feeds/ Supplements |
Characteristics |
|
Weight loss not due to liver or kidney failure |
12 to 14% protein 7 to 10% fat High digestibility Easily chewed |
Grass/legume mix hay Complete pelleted or extruded feeds Good quality pasture 1/4 to 1 cup vegetable oil/day Beet pulp (soaked) Soybean meal (1/4 to 1/2 lb per day) Avoid poor quality or high fiber hay |
|
Inadequate dentition |
Easily chewed |
“Soups” of complete pelleted or extruded feeds Soaked hay cubes or beet pulp Avoid coarse hay and dry pelleted feed |
|
Pituitary/thyroid tumors |
Reduced starch Highly digestible fiber Increased vitamin C |
Complete pelleted or extruded feeds Good quality hay or pasture (if not foundered) 5 mg vitamin C daily Avoid sweet feeds |
|
Kidney failure |
Restricted calcium protein phosphorus |
Grass hay Corn milo Complete feeds designed for maintenance horses Avoid legumes, wheat bran, beet pulp |
|
Liver failure |
Restricted protein Increased starch Increased B-vitamins Increased vitamin C |
Grass hay corn, milo Sweet feeds designed for maintenance B-complex supplement 10 gm vitamin C daily Avoid legumes, high fat rations |
References
Ralston, S. L. 1989. Digestive alterations in aged horses. J. Eq. Vet. Sci. 9:203-205.
Ralston, S. L. et al., 1988. Differences in diagnostic test results and hematologic data between aged and young horses. Am. J. Vet. Res. 49:1387-1392.
Ralston, SL. 1990-1993. Unpublished data.