Conditioning the Older Horse
What are the effects of advancing years on athletic performance? Are there special considerations in the conditioning and general care of older horses? Is regular exercise beneficial for older horses or, conversely, does the extra wear and tear on joints, tendons, and ligaments only hasten development of crippling lameness problems? Nowadays, these questions and others are asked frequently. In part, this is a reflection of the ever-changing role of horses in society. Demographic information suggests that older horses (more than 15-20 years of age) comprise a large proportion of the overall horse population. In fact, some surveys indicate that more than 15% of the horse population is over 20 years of age. More than ever, the horse is a treasured companion, and we strive to ensure that this rewarding relationship lasts for as long as is reasonably possible.
Our expectations for length of athletic career also are changing--in many athletic disciplines, there are numerous examples of horses remaining highly competitive until their late teens or beyond. Of course, not all horses will be able to compete at the top of their games at that age and, generally speaking, we should lower our expectations in terms of athletic performance as the horse ages. Nevertheless, with appropriate care and conditioning, there is no reason why the older horse cannot be used for pleasure riding, and perhaps more.
What Is Old?
Just what do we mean by old? There are no hard and fast rules--we do know that few horses survive into their 30s or 40s, but many horses do quite well until their late 20s. "Geriatric" and "senior" are terms frequently used to describe horses in this age bracket. However, geriatric really refers to old humans or animals with problems and diseases. Old, but otherwise heal-thy horses are just that--old.
The adage "you are only as old as you feel" also applies to horses. Some horses might begin to "slow down" in their late teens, while others can remain quite vigorous up into their mid-20s. The reason for this difference is unknown. As in humans, it is possible that genetics, diet, and exercise history play some role in determining vitality in old age, and ultimately, the life span of the horse.
Aging And Athletic Capacity
Before considering some aspects of the care of older horses, let's briefly examine what is known concerning the effects of age on athletic capacity. Although there has been very little research on the effects of aging in horses, we will examine the situation in humans to gain some insight and review what is known about the horse.
All measures of physical performance or "functional capacity" will decline with age. However, not all functions decline at the same rate, and there will be considerable variation between horses. In humans, it is known that the effects of aging are greatly influenced by regular exercise. Whether this is true of horses is not known.
In humans, the age-related decrease in exercise ability is explained by changes in the function of several body systems. Between the ages of 25 and 80 years, there typically is a 40-50% reduction in muscle mass, even in healthy individuals. This lost muscle mass tends to be replaced by fat. As a result, we experience a very large decline in muscular strength. The transfer of electrical impulses along nerves is slowed, contributing to a decrease in agility and speed. There also is a progressive decrease in maximum aerobic capacity (VO2max), due to a decline in the maximum exercise heart rate and a reduction in the capacity to deliver oxygen to the working muscles.
In short, we lose speed, strength, and endurance with advancing years. We also tend to be less tolerant of the heat, partly because of the decline in cardiovascular function. This means that the elderly have to be more careful when exercising in hot conditions.
Dr. Ken McKeever, PhD, MS, and col-leagues at Rutgers University have investigated some aspects of the effects of age on athletic performance in horses. In one study, the researchers compared exercise responses in two groups of six untrained mares (Thoroughbreds and Standardbreds), one "young" and one "old" (see McKeever and Malinowski 1997). The average age of the horses in the young and old groups was five and 22 years, respectively. Both groups of horses undertook an incremental exercise test on a treadmill to allow measurement of VO2max and endurance capacity. In this type of test, the horse starts at a trot, with a stepwise increase in speed every 60 seconds. The test is completed when the horse can no longer maintain the speed of the treadmill.
The VO2max of the young mares was considerably higher--approximately 25% higher than the older horses. In addition, maximum speed attained during the test and the total run time were, respectively, 24% and 52% higher in the younger compared to the older mares. So, as in older humans, it is likely that the aerobic capacity of horses declines with advancing years. As well, this reduction in VO2max contributes to decline in endurance capacity. In practical terms, this means that for any given running speed, the older horse will be working at a much higher percentage of their aerobic capacity (he/she is working much harder and will tire sooner).
What McKeever and his colleagues could not determine from their studies was whether the lowered exercise performance in the old mares was due to aging alone, or in part due to a prolonged period (years) of inactivity before the study. Studies in humans indicate that, among other factors such as genetics, activity pattern greatly influences the rate of decline in aerobic capacity.
On average, beyond 40 years of age, human VO2max decreases by 10% every decade. However, regular exercise through the 30s, 40s, and 50s will limit the decrease in aerobic capacity. A similar effect might occur in horses which are maintained in training throughout their teen years and beyond, allowing them to remain competitive during that period.
Although some decline in aerobic capacity is an inevitable consequence of aging, it is important to emphasize that even people in their 70s and 80s can benefit from physical conditioning--a combination of aerobic (e.g. jogging or swimming) and resistance (weight) training leads to improvement in VO2max and muscle strength and, as a result, an overall improvement in the quality of life. While this is likely to be true of older horses, more research is required to determine just how much exercise is necessary to produce beneficial responses. Meanwhile, it is prudent to adopt a conservative approach when developing conditioning programs for older horses.
As mentioned, we know very little about methods for conditioning the older horse. Perhaps some of you are concerned about the safety of exercising the older horse. However, provided the horse is free from major lameness problems and is in good general health, there is no reason not to undertake a moderate conditioning program. Having said that, it is difficult to make "blanket" recommendations regarding the type of conditioning that will work for all horses. Each horse is different, and you (possibly with the help of your veterinarian) are going to be the best judge of what your horse can and cannot handle.
The type and extent of conditioning primarily will depend on several factors, including the age of the horse, training history, body condition, and the main goal of the conditioning program. For example, the amount of training that is reasonable for a 15-year-old horse will likely be considerably greater than for a horse in his mid-20s. However, regardless of age, we need to consider the horse's training history carefully. There are many eventers, show jumpers, and endurance horses which have sustained a high level of fitness throughout their teen years--those horses appear capable of training and competing at a level not far below that of a much younger horse. However, because they are well-schooled in their respective events, these seasoned campaigners often can remain competitive with a lower training volume. This helps reduce excessive wear and tear on the musculoskeletal system.
The situation will be much different for the middle-aged and older horse which has received little exercise for a number of years. A much more cautious approach to conditioning is required. As well, there is an impression among riders and trainers that those horses take more time to attain fitness compared to the youngsters. Therefore, you must start out very gradually, be patient, and closely monitor your horse for signs that indicate you are overdoing it. For horses of any age, injury and lameness can occur when the training volume is increased rapidly. Carefully palpate tendons and ligaments of the lower limbs for signs of heat, swelling, and pain.
Obviously, the level of training also will depend on whether or not you are aiming to compete your horse. This is a reasonable goal for the teenager, but (in most cases) less reasonable for the horse in his mid-20s. More realistic is a program of regular light exercise that helps maintain body condition and muscle tone, and allows the horse to be used for trail riding or similar tasks. This is a win-win situation--regular exercise will help prevent or even reverse some of the age-related changes in muscle mass and strength, and will also improve your horse's quality of life. Daily turnout is another way to ensure that the horse receives regular exercise, and is certainly important for maintaining good spirits.
Here are some points to bear in mind.
First, preserving soundness is a very important consideration. If your horse has chronic lameness, it will limit the amount of work that can be undertaken--meaning that your horse might not be sound for riding, and that horse cannot gain the health benefits associated with extensive physical conditioning. Unfortunately, the years of wear and tear inevitably take their toll, and some level of aches and pains is the norm rather than the exception.
It's a good idea to ask your veterinarian to examine your older horse before putting the previously idle horse back into work. Lameness associated with foot pain (e.g. navicular syndrome, see page 117) is common in older horses, and some medication as well as special shoes might be necessary. Pain associated with degenerative joint disease is common; again your veterinarian will be able to identify these problems and make recommendations concerning pain relief and exercise programs.
It is advisable to schedule regular veterinary check-ups, particularly for horses in their 20s. Keep a close eye on the joints, tendons, and ligaments of the legs--any stiffness or swelling might signal the recurrence of an old problem and the need to moderate the conditioning program.
Start out slow and err on the side of caution. As a guide, do not increase the weekly training distance by more than 5%. Three 10-15 minute sessions per week on the longe line or under saddle might be an appropriate place to begin--the length of these workouts can be increased over the next month. Then, you can add another weekly session and/or begin to increase the intensity of the workouts gradually by inserting some low-speed cantering. Try to vary the workouts as much as possible to maintain the horse's interest. If possible, include a little hill training--this will help muscles strengthen.
Be cautious during the hot summer months, particularly when beginning training during the summer. Older humans and animals are often less able to lose body heat during exercise, in part because of a decline in cardiovascular performance and a reduction in sweat gland function. For that reason, it is wise to limit exercise on very hot days--either shorten the duration of work or reduce the intensity of exercise. In hot weather, actively cool the horse after exercise by applying cold water over the neck and body. Also allow him to drink a moderate amount of water after exercise to replace fluid losses due to sweating.
Medications, Diet, And Routine Care
By now, most of you are quite familiar with the myriad of supplements and medications available for management of joint ailments. Horses with confirmed degenerative arthritis in one or more joints might benefit from intra-articular injections of hyaluronic acid or polysulfated glycosaminoglycans (PSGAGS)--treatments that are believed to slow the progression of joint inflammation. Nutraceutical compounds containing glucosamine and chondroitin sulfate also offer some promise in the management of joint ailments. In either case, a decision regarding the need for these treatments is best made by your veterinarian. (For more information on joint supplements, see "Joint Supplements" in the November 2000 issue of The Horse or go to http://www.thehorse.com/ViewArticle.aspx?ID=100.)
In some parts of the world there has been interest in the effects of hormone treatments in older horses. Specifically, a synthetic form of equine growth hormone is available for use in horses, but is not licensed in the United States or Canada--the following information is for your interest only (also see the papers by Malinowski et al. 1997 and McKeever et al. 1998).
Growth hormone (GH) is an important stimulus for protein synthesis and tissue growth throughout the body. We also know that GH levels decline with age. Therefore, a relative deficiency in GH might contribute to the loss of muscle mass and strength observed in older humans and animals.
In one study, old mares (20-26 years) were treated with equine GH for six weeks. Feed intake, body weight, body condition score, and muscle condition were monitored during treatment. Neither feed intake, body weight, nor body condition scores were altered during the period of GH treatment. Subjectively, however, muscle definition was improved in the GH-treated mares.
These researchers also studied the effects on GH treatment on aerobic capacity and exercise performance in this group of unfit mares. They found that three months of GH treatment did not affect aerobic capacity or other measures of exercise performance. So far, it appears that GH treatment is not a "magic bullet" for the reversal of age-related decreases in function; a program of regular exercise is likely to be considerably more beneficial.
You also should pay close attention to diet. In the last couple of years, there have been excellent articles in The Horse concerning the nutritional requirements of "senior" horses; for example, see "Cuisine for the Golden Years" in the May 2000 issue of The Horse, or go to http://www.thehorse.com/ViewArticle.aspx?ID=179. As with younger horses, forage (grass and hay) and other fiber sources should form the foundation of any diet for the older horse. These fiber sources provide a lot of energy and are vitally important for maintaining the health of the large intestine. Grass (except for horses prone to episodes of laminitis) and early cut grass hay (such as timothy) are good sources of fiber. A good alternative, particularly for horses in moderate work, is beet pulp--this highly digestible fiber provides as much energy as oats. (See "Feeding Beet Pulp" of the May 1999 issue of The Horse or go to http://www.thehorse.com/ViewArticle.aspx?ID=314)
Some older horses have difficulty maintaining body weight, particularly in the winter months in cooler climates. Adding energy-dense, digestible fats and oils (e.g. corn oil or rice bran) to the diet can help maintain body condition in these horses. To simplify feeding programs, an alternative approach is to use a commercially available "senior" feed. However, according to Sarah Ralston, VMD, PhD, Dipl. ACVN, of Rutgers University, you should have blood drawn and tested before putting a horse on a "senior" ration to check for pre-existing hepatic or renal dysfunction, since the typical "senior" formulation might aggravate these conditions.
Senior feeds come in two forms--a concentrate that is to be fed with hay, and a "complete" feed that contains adequate fiber when fed alone. These diets are formulated to meet the nutrient requirements of older horses and are highly digestible. The complete diet form is particularly useful in horses with dental problems (e.g. overly worn teeth, tooth loss, or wave mouth). Those horses can suffer digestive problems and weight loss when fed standard diets because of difficulty in properly chewing their food.
With input from your veterinarian and equine nutritionist, you can design an exercise program tailored to your horse's needs that will help improve his quality of life and his life expectancy.
Holland, Robert E. Understanding the Older Horse 1999.
Malinowski, K.; Christensen, R.A.; Konopka, A.; Scanes, C.G.; Hafs, H.D. Feed intake, body weight, body composition score, musculation, and immunocompetence in aged mares given equine somatotropin. Journal of Animal Science 1997; 75: 755-760.
McKeever, K.H.; Malinowski, K. Exercise capacity in young and old mares. American Journal of Veterinary Research 1997; 58: 1468-1472.
McKeever, K.H.; Malinowski, K.; Christensen, R.A.; Hafs, H.D. Chronic recombinant equine somatotropin (eST) administration does not affect aerobic capacity or exercise performance in geriatric mares. The Veterinary Journal 1998; 1: 19-25.
McKeever, K.H., Malinowski, K. Endocrine responses to exercise in young and old horses. Equine Veterinary Journal 1999; Supplement 30: 561-566.
About the Author
Ray Geor, BVSc, PhD, Dipl. ACVIM, is professor and chairperson of Large Animal Clinical Sciences at the College of Veterinary Medicine at Michigan State University
POLL: University Equine Hospitals