But each horse ages differently, and while these signs might be readily evident in some long-in-the-tooth steeds, they might be invisible in others. “The scientific community has defined the horse as physiologically showing signs of aging at 20 and older,” says Karyn Malinowski, PhD, professor at and founding director of the Rutgers Equine Science Center . However, she identified very few of these signs during a 12-week exercise-research trial involving horses over age 25 from the Center’s herd. “They were lining up at the gate to get on the Equi-cizer,” she recalls. “Turned out afterward, they bucked and kicked and reared, tails up in the air, running around the pastures. I firmly believe they felt better using those old joints.”
Similarly, Malinowski’s own horse, a former Standardbred racer named Magic, happily foxhuntined as a senior. “But if I X rayed his legs, I’d want to cry,” she says. “Irrespective of how old horses are, I think we do them the most good by keeping them moving—and, as much as possible, keeping them outside. They love to exercise, and outdoors they continue to exercise. If a healthy older horse is just standing in a box stall, we’re doing him no favors.”
Still, no matter how spritely your senior might seem, he continues to age, and he will fare better if you detect and respond appropriately to aging’s effects.
Establish a Base Line
If your horse’s normal TPR measurements (temperature, pulse, and respiration) are already posted where you and your veterinarian can find them easily, great. If not, now is a fine time to obtain and record them. Get an even more complete picture of his health by including two more numbers: weight (calculated using a weight tape, TheHorse.com/tools/horse-weight-calculator) and body condition score from 1-9. Also, photograph him from several angles and archive the photos where you’ll find them easily.
Now, instead of relying on memory alone, you can refer to a base line data set and images when you’re assessing your horse in the months and years ahead. Most age-related body changes happen too gradually to notice if you see your horse every day. But if you compare the starting and current numbers and appearance regularly—say the first of each month—you’re equipped to detect subtle differences. Consult your veterinarian about these shifts, and he or she might be able to help you slow or even counteract some of aging’s negative effects.
It’s imperative that senior horses get a thorough annual veterinary checkup—including a complete oral examination. Adult teeth, which continue to erupt slowly from the gum as they wear, normally last a lifetime, but very old horses might have so little of one or more teeth left that they’re no longer anchored in the gums. Loose, they interfere with chewing and cause pain. Such teeth need to come out; once they’re pulled, these horses will be much more comfortable.
As your horse ages, and especially if health problems develop, ask your veterinarian if more frequent checkups are advisable. Between visits, call whenever a question crops up.
If senior horses develop a condition that only surgery can correct, one natural but, perhaps, tough-to-ask question is whether benefits justify cost. For colic, we can look to research for guidance with the decision, says Amy Johnson, DVM, Dipl. ACVIM, assistant professor of Medicine and Neurology at the University of Pennsylvania and a staff member at Penn’s New Bolton Center (NBC) large animal hospital. She cites a 2010 study by her NBC colleague Louise Southwood, BVSc, PhD, Dipl. ACVS, ACVECC, showing that “older horses that have had colic surgery for certain conditions actually do as well as younger horses. People may be reluctant to pursue things like colic surgery with an older horse because they assume the animal won’t do as well afterward. Of course, there are other reasons not to pursue surgery. But the assumption that there’s a worse prognosis is not correct in many cases.”
Senior horses—like humans—tend to lose lean body muscle mass and replace it with body fat (adipose tissue), Malinowski says. This poses problems for two reasons:
First, most horses over 20 have at least some arthritis. Carrying extra weight exacerbates that discomfort. “As you know if you’re heavy yourself, the knees are the first things to go,” she says. “So a wonderful reason to keep your horse fit and keep his body condition score between 5 and 7 is to keep weight off those joints.”
Second, as the body ages, it becomes more resistant to insulin, a hormone that’s responsible for controlling blood sugar (glucose) levels by signaling fat, muscle, and liver cells to take up blood glucose and store it as glycogen; this reduced sensitivity to insulin diminishes the body’s ability to metabolize glucose. The condition, which is similar to Type 2 diabetes in humans, is also exacerbated by excessive body fat.
The healthy horse’s body responds to exercise by producing more of the hormone cortisol, which mobilizes glycogen stores, “producing more glucose and refueling working muscles so the equine athlete can recover quickly,” Malinowski explains. “It also acts as an anti-inflammatory agent.”
But researchers have shown that senior horses’ cortisol levels don’t rise as much after exercise as those of younger ones; thus, “the older horse isn’t as protected by those anti-inflammatory properties and also doesn’t get the glycogen-metabolism cycle kicking in as much,” she says. So recovery after exertion takes longer in these equine senior citizens.
Senior Staying Power
Despite the horse’s “wonderful innate ability to exercise,” Malinowski says aerobic performance decreases after age 20. Maximal heartbeat and stroke volume (the volume of blood the heart ejects during each heartbeat) both begin to decrease, so the total cardiac output (a combination of heart rate times stroke volume) of the horse over 20 is significantly lower than that of a younger horse.
For this reason, she says, it’s important to be careful when exercising senior horses in hot, humid weather. “His heart works harder and his inner core temperature reaches 105°F (40°C) sooner than his younger counterparts’,” she explains. “Even if the horse is sweating appropriately, he cannot go as long or as far.”
However, Rutgers researchers have also found that “10 minutes after exercise stops, there’s no difference in heart rate (compared to younger horses), and recovery is very quick (in both older and younger athletes),” Malinowski says. “The older horse’s cardiac output is sufficient to thermoregulate its body in the heat—the ability to just stand around sweating in hot weather is similar to younger counterparts’—but not to exercise and thermoregulate.”
Immunity Issues in Senior Horses
Also after age 20, Malinowski says, a horse’s “ability to respond to infection or disease is not what it was.” Fortunately, the senior horse’s risk of exposure to pathogens might be reduced because he’s not regularly trailering to shows, mingling with unfamiliar horses, and staying in strange barns. However, new arrivals at your home barn can carry infectious agents. Keep any unfamiliar horse well away from your older horse, both in the barn and on turnout, and never share equipment such as water buckets, tack, or blankets.
As for vaccinations, senior horses “do respond to a vaccine challenge (developing an antibody response) for things such as influenza, but not for as long as a younger horse and not to the degree of antibody production (that younger animals exhibit),” Malinowski says. “And a question we don’t yet know the answer to is: Can we make up for this deficit by giving a higher dose of the vaccine? Or giving it more often?”
Until researchers answer that question, she recommends giving senior horses “their routine vaccinations in the spring, with possibly a booster for things such as encephalitis (Eastern equine encephalomyelitis, West Nile virus, etc.) in the late summer to early fall as well, just as a preventive.”
Malinowski advocates deworming senior horses based first on whether it’s even needed and then on what type of parasite you’re seeing. “In 10°F weather, there aren’t any parasites crawling up blades of grass, so why would you deworm in the middle of winter?” she says. “With warm soil and wet conditions, yes, you do want to deworm. But do fecal egg counts first and identify the parasite that’s present, so you can determine which anthelmintic to use.”
Assuming he has some level of arthritis, how well the older horse moves and performs depends on how comfortable he is in his joints, Malinowski says. To stave off Magic’s possible aches, she administered a gram of phenylbutazone before leaving the farm to foxhunt and another gram upon returning. Overused, non-steroidal anti-inflammatory medications such as this can be hard on the stomach lining. “But if an old schoolhorse needs a gram of Bute a day to be comfortable, so be it,” she says.
Veterinarians report anecdotal success using joint health supplements such as glucosamine and chondroitin in horses with osteoarthritis. But Malinowski cautions that not all of these products have been tested in horses to the clinical standards required for drug approval. She notes, however, that regular mild exercise itself can, in some cases, ease aches. “Again, that’s why I love horses being outside: They’re constantly moving around,” she says. “As the old adage says, ‘Use it or lose it!’ ”
When keeping senior horses in stalls, make sure bedding is deep enough to be comfortable but not so deep that he can’t easily get up again. “And rubber mats are wonderful,” Malinowski adds.
Nutrition for Senior Horses
What’s appropriate for an aging horse’s diet depends on the individual, says Johnson. The state of the teeth is one consideration; what else is going on in his body is another. “Some horses can be maintained on whatever diet they’ve been on for their whole lives,” she says. “Horses with laminitis problems may need low-starch/low-sugar diets, including hay tested to make sure it’s not high in starch and sugar.”
Those with compromised dentition—usually evident as quidding (chewing and then dropping food, rather than swallowing), food dribbling out the side of the mouth, slower eating, and weight loss—might need their food processed into a gruel or slurry to make nutrients more accessible and prevent choking.
“For horses that have good teeth and that aren’t obese or prone to laminitis, the best food is by ‘Dr. Green Pasture,’ ” Malinowski says. “There’s no substitute for good-quality fiber—roughage—in the diet, no matter how old the horse. You may just have to accommodate, based on dentition, as to what type of fiber.”
“Geriatric horses with severe tooth problems need feed that’s essentially prechewed,” says Jack Easley, DVM, MS, Dipl. ABVP, who practices equine dentistry in Shelbyville, Kentucky. “That’s what ‘senior’ feeds are: hay, grain, minerals, and whatever else the horse needs, ground up and formed into pellets that dissolve in the mouth, with no need to be chewed any more. You can stretch the life span of a horse well beyond the point where he doesn’t have any teeth by feeding him correctly.”
As long as you feed your senior an appropriate diet, says Johnson, you probably don’t need to supplement vitamins and minerals; good forages and most supplemented grain diets include these. However, “a horse on a restricted-grain diet may need some kind of ration balancer to make sure he’s getting the recommended level of vitamins, particularly when hay quality is less than ideal,” she explains. Keep in mind that if you’re oversupplying vitamins and minerals, “the only thing you’re really doing is making very expensive urine—because horses eliminate what they don’t need.”
Visit with your veterinarian about the designing the best ration for your senior horse. Also, keep an eye on the feed bucket; if your horse is leaving food, you might need to change his diet.
Additionally, note how your older horse maintains body weight and condition in the chill of winter and the heat of summer. “Older horses are stressed more in both cold weather and hot weather,” Malinowski says. These extremes might dictate adding calories to senior horses’ diets.
Even the healthiest senior horses can’t live forever. But our sources say you’ll give yours the best chance of living comfortably for as long as possible if you keep track of how his body is changing, stay in contact with your veterinarian, and remain alert for signs of ADR: ain’t doin’ right.
“If horses are not their normal selves, that’s when to start looking for what’s going wrong,” Malinowski says. “They always tell you.”