Older horses, like older people, tend to have some health problems. As our equine preventative health care improves, the lives of our horses grow longer. Virtually any health issue can be seen with a senior horse, but some health problems are far more common than others. Here are three issues to prepare for as you work to maintain your older horses.
Arthritis is certainly not confined to older horses, but it typically gets worse with age and may even appear in an older horse that did not have problems at a younger age. Part of the problem is that the basic maintenance processes slow down as the horse ages. The cartilage proteoglycans-like chondroitin sulfate and hyaluronic acid-decrease in cartilage during the aging process.
Older horses also lose muscle mass and can be more prone to weaknesses in the tendons and ligaments. This, in turn, affects the joints because these tissues help to stabilize joints and prevent abnormal movements that can cause damage. Finally, older horses are often less active, which contributes to all the age-related changes above.
It used to be that the only advice you would get from your veterinarian for treating or managing an arthritic older horse was to put him on phenylbutazone. This drug is still useful, but we now know it can come with a price in terms of toxicity. Gastric ulcers, right dorsal colon ulcers, and kidney damage are all possible side effects of regularly using "bute" to treat arthritis symptoms. Because of this, it's better to reserve use of phenylbutazone for times when the horse has a very painful flare up. Even then, be wary of using it for more than a few days at a time and always use the lowest dose possible. If the horse needs longer-term pain relief, consider herbal alternatives such as Devil's Claw or the herbs with natural aspirin-like activity, like Meadowsweet and White Willow Bark.
Keeping the older horse in light work is actually beneficial for the joints, muscles, ligaments, and tendons. Light work can do a lot to prevent muscle loss in older horses and keeps the horse more limber. It is particularly beneficial for cartilage. Cartilage has no blood supply. It gets the nutrients it needs from the joint fluid. Cartilage is compressible, similar to a sponge. As the horse moves, fluid is forced out of the cartilage when the joint is loaded, and fresh fluid rushes in again when the weight is lifted.
Several nutrients are of particular importance to cartilage and other connective tissues. These include Vitamin C, B vitamins, copper, and zinc. Horses can make their own Vitamin C, but this capacity decreases with age in other species so it may also decrease in the horse as well. B vitamin supplies come predominantly from the hay and grass a horse eats, but they also come from microorganisms in the intestines. If the horse has any intestinal issues, supplementation may be wise. Finally, copper and zinc are two of the most common mineral deficiencies, and the effects of this deficiency are made worse if iron and manganese are high-as is often the case.
Perhaps the best thing ever to happen for older horses with arthritis was the introduction of joint supplements. Older horses often have dramatic responses to joint supplements, such as glucosamine and chondroitin. These supplements also stimulate production of better levels of proteoglycans in cartilage from older animals. Start with a basic glucosamine and chondroitin supplement. If your horse is prone to severe flare-ups of arthritis pain and inflammation with hot joints, try hyaluronic acid during those times. Although there are no equine studies yet, hydrolyzed collagen (also known as hydrolyzed gelatin) has been shown in older humans to help stem the tide of arthritis and also help maintain bone density.
For older horses whose joints are very stiff, consider Neoprene wraps for part of the day. These are available for hocks, knees, and fetlocks. They both trap heat and provide gentle support for the joint. Many horses are helped greatly by these wraps and they are not expensive. Some older horses also respond favorably to magnetic wraps.
Trouble Holding Weight
Maintaining a healthy weight is an extremely common problem in older horses. Dental problems are often the cause of weight loss (see the related article in Good Horsekeeping on page 18 of this issue). But this can occur even when the teeth don't appear to be an issue. Unrecognized dental pain-such as an abscess or jaw/temporomandibular pain-is sometimes the cause, but for many older horses no oral or dental issue is found.
Elderly humans can develop decreased saliva production, which commonly causes them to experience swallowing problems. Saliva is both an important lubricant and also a fluid and bicarbonate buffer for the intestinal tract. Older humans also may develop decreased production of stomach acid. This may sound like a good thing on the surface, but stomach acid is needed as the first step of protein digestion, and it also helps kill harmful bacteria before they can reach the intestinal tract. If both of these problems develop in older horses, they can easily lead to weight loss due to poor digestion and poor absorption of nutrients.
It's not unusual for older horses to have smaller populations of fermenting bacteria and protozoa in their colons. This can lead to an inefficient use of the fiber in their diets.
Older horses kept in a herd may not be competing effectively for available food. They also might be bullied by the younger horses, which can lead to stress and possible stomach ulcers. Finally, older horses often have poor resistance to internal parasites compared to younger adults, so they may need a special deworming schedule.
Strategies for Managing Weight Issues
The first step is to have your veterinarian rule out any underlying disease or dental problem. Also watch your horse carefully when he's eating. If he chews very slowly and takes a long time to eat, he may be experiencing pain or difficulty in swallowing.
If all correctable causes have been ruled out, the horse needs a diet change. Senior diets were devised to meet the special needs of older horses, and they do a very good job, too. However, they may be too expensive for some owners. One strategy for cost control if this is an issue is to copy down the analysis figures from a bag of senior feed and shop around for a regular complete feed that is similar. A horse that is having serious weight issues is going to need most, if not all, of his diet to come from processed feeds.
The major advantage of processed complete or senior feeds is that they are more digestible. Because of the small particle size, they are essentially pre-chewed. Processing of the grain portion in these feeds-e.g., extrusion, pelletizing-also increases the digestibility of the starch. Fortification with vitamins and amino acids helps make up for shortcomings in the digestive tract function. Use of easily fermented fiber sources like alfalfa and beet pulp gives the feed a prebiotic effect.
If the commercial feeds are still too pricey, you can make your own senior diet using alfalfa pellets or meal, beet pulp, processed grains (e.g., steamed oats) and things like wheat bran. You'll need help from your veterinarian or an equine nutritionist to make sure the diet is properly balanced and fortified.
Feeding wet meals can make a huge difference with an older horse. Whether this helps them swallow, replaces fluid from decreased saliva production, or simply supplies water when the horse is not drinking enough (water is critical for good digestion) is not clear-but it works! You should also guarantee the horse is getting the minimum daily salt requirement by dividing it up between meals. This will keep water consumption up. A probiotic or prebiotic bacterial fermentation product helps some older horses. Finally, make absolutely sure that the older horse has sufficient time to finish meals and is not having his food taken by other horses.
Cushing's Disease is the common name for pituitary pars intermedia dysfunction, or PPID. It has been said that any horse that lives long enough will develop this hormonal problem, and that's probably true.
PPID is caused by oxidative stress to particularly vulnerable neurons in the brain, the nerves that produce the brain chemical dopamine. Without normal levels of dopamine, the brain overproduces several hormones. Overproduction of prolactin can cause the udders of mares with PPID to swell and even drip milk. Overproduction of ACTH causes elevated levels of cortisol, which causes problems with muscle loss, insulin resistance, laminitis, increased drinking and urination, increased risk of tendon/ligament injury, and a weakened immune system. Allergies, skin problems, and sweating abnormalities may develop. The hormonal shifts also cause the horse to develop an abnormally long coat that may be wavy or curly. The coat changes are the "classic" symptom of PPID, but laminitis and insulin resistance may develop years before this occurs. An unexplained fall laminitis in an older horse that has never had this problem is a red flag warning of early PPID.
Dealing with PPID
There is no cure (yet) for PPID, but it can be controlled. When they are properly treated, horses with PPID can live out their lives and die of totally unrelated causes. However, this is one condition where you don't want to experiment or fool around with questionable treatments. The consequences for the horse are too severe. Laminitis is one of the most painful things that can happen to a horse. Inadequately treated horses can also develop fatal infections in their head, mouth, or lungs.
The most reliable therapy is to use the drug pergolide. For best results, your veterinarian may follow the horse's ACTH hormone level and adjust dose until this measurement is back to normal levels. Checking this level once a year after that is adequate. Fall is the best time to check, since this is when hormone levels are the most difficult to control.
The herb Vitex agnus-castus-Chastetree berry-works well for some PPID horses, but it is not as reliable as pergolide. If you try it, it is very important to follow hormone levels. There are also many horses that respond well to it initially but eventually have to be switched to pergolide.
For some horses, pergolide is all they need to control their symptoms. For others, the laminitis and insulin resistance will not come under good control with pergolide alone. These horses also need a special diet that is very low in starch and sugar. Many feeds claim to be safe and low or reduced starch/sugar but they often are not low enough. A diet of plain (no molasses) beet pulp and hay or hay cubes/pellets with a combined sugar and starch level of 10% or lower is usually required. Vitamin E should be supplemented, along with minerals as needed to balance the diet and avoid deficiencies. For more details on managing the horse with PPID and insulin resistance, visit the Equine Cushing's and Insulin Resistance group at http://pets.groups. yahoo.com/group/EquineCushings.
While older horses do have some special health needs, many of the issues associated with arthritis, weight loss, and Cushing's Disease can be managed so that you can enjoy many more special years. Those of us who have had the pleasure of knowing and loving an older horse also know that any extra work is worth it!