Feeding Older Horses: Cuisine For The Golden Years
Is your horse old enough to vote? Then he's an equine senior citizen by some standards. These days that's not so rare; more and more horses are living into their 20s and 30s, and even beyond. This is a direct result of the improved level of veterinary care we've been able to provide for the last 30 years or so. In particular, the availability of modern deworming medications, such as ivermectin, is widely considered the biggest single contributing factor to our horse's newfound longevity.
Nutrition plays a role as well. Horses which have been correctly fed all their lives are far more likely to live to a ripe old age than those which have been starved or those which have struggled with obesity and its frequent partner, laminitis. That, too, should come as no surprise; the same is true of humans. Diet affects the function of virtually every system in the horse's body -- from the firing of his muscles (fueled by dietary energy sources like carbohydrates and fats) to the formation of new tissues (facilitated by the "building blocks" in protein called amino acids) to the function of his every chemical system (which requires trace minerals such as magnesium, sulfur, and cobalt to help form enzymes, hormones, and other influential "messengers" for the cells).
As your horse ages, however, all of his systems slow down a little. He begins to need more fuel to do the same tasks. His eyesight and hearing might become a little less acute, his legs move a little less swiftly. His gastrointestinal tract can become less efficient at extracting the nutrients he needs from his food. At the same time, his body's ability to thermoregulate (maintain an even body temperature) gradually decreases, so he might need extra dietary energy to help him stay warm in winter, and assist him in coping with heat and humidity in summer.
Compounding his dietary difficulties is the likelihood that his dental health isn't what it used to be. Equine teeth continue to grow throughout a horse's life, and it's not uncommon for older horses to run out of teeth before they run out of life. As the length of the reserve crowns on his molars dwindles, the teeth become less stable within the jawbone, and more susceptible to dental disease and loss. Or, if they do stay put, they simply can wear down until there is very little grinding surface left. Without the ability to properly chew the tough, fibrous pasture and hay his diet is built on, an aged horse is at risk of serious malnutrition.
Faced with these challenges, it's no wonder older horses tend to lose weight and muscle tone and begin to look like hat racks. Fortunately, there's quite a bit we can do to help a horse receive correct nutrition through his golden years. It just takes a little extra TLC.
The prospect of dentures for horses is still somewhere off in the distant future, but there are a number of strategies we can use to help him make the most of the teeth he has left.
Not every older horse has poor dentition, of course -- my own 29-year-old pony, Pokey, has excellent choppers for his age, and (so far) has no difficulty chewing hay or whole grains. But if you notice your senior citizen "quidding" (dropping large mouthfuls of half-chewed hay out of his mouth), or see long stems of forage and lots of whole grains in his manure, those are indications that he's experiencing some difficulty. First, call your veterinarian out -- it's possible your horse just is overdue to have his teeth floated, rather than suffering a dental dead-end. Older horses might need more frequent dental care than their younger kin, so it's a good idea to have them checked at least once every six months.
If it's clear, however, that your guy just doesn't have much left to grind with, you will have to do some of the grinding for him. That way, the nutrition in the feed will be more available to his digestive system, and you'll lower the risk of choking and colic that he'll run if he continues to struggle with long-stemmed hay and whole grains.
Start by offering him softer, more palatable hay; a switch from a mature grass hay to a hay cut at an earlier stage of growth. If he still can't manage, consider purchasing a heavy-duty leaf shredder and chop his hay before every meal. The shorter stems (a couple of inches in length) will be far easier for him to chew and swallow. If you chop his hay, though, remember to weigh it beforehand to make sure you're offering him a comparable amount to what he was eating before. Once the hay is chopped, it gets very fluffy, so it will be difficult to estimate how much you're giving him. However, using hay cubes is easier than chopping it yourself. There are timothy/alfalfa or whole plant alfalfa cubes that are available.
You also might want to avail yourself of other forms of highly digestible fiber to help boost your horse's overall intake, especially if you notice that he has trouble grazing; you won't be able to depend on pasture to help him maintain his weight anymore. Soaked sugar beet pulp is one excellent solution. It's soft and easy to chew, and equally easy for the gut to process. You also might investigate feeding hay cubes, which are compressed rectangles of chopped forage. (The cubes are a better choice than roughage chunks or pellets, in which the fiber pretty much is pulverized.) Indigestible fiber, the portion of the plants that gives the stems rigidity, still serves a purpose in the equine diet -- it aids in gut motility (the ability of the digestive tract to keep everything moving along nicely). Hay cubes, in which the fiber is chopped into pieces an inch or two in length, retain some of this "scratch factor."
Instead of whole grains, your older horse probably will do better with concentrates that have undergone some processing to make their nutrients more available to him. Cracked, flaked, or rolled grains have had their seed coats broken so that they're easier to chew. Because some nutrients, especially vitamins, break down rapidly when exposed to the air, it's important to buy small quantities of grains processed this way, and to feed them as fresh as possible. Dust might also be a consideration with rolled or cracked grains, something to keep in mind if your older horse has respiratory problems.
Pelleted feeds are made with grains that are ground and held together with a binding agent, and they're another good choice for the geriatric horse. You can even soak them in warm water, or a mix of water and molasses, to make a gruel for a really toothless animal. (The same is true of hay cubes, by the way.) Some older horses thrive on extruded feeds, which are cooked under steam pressure to gelatinize the starches in the grains and make them more available for absorption in the gut. (More on extruded feeds next month.) The kibble-sized nuggets of an extruded feed might be difficult for a toothless horse to handle, but for many geriatrics who aren't quite that far gone, the nuggets make an inviting feed; manufacturers claim they are low-density, gentle on teeth, and can be soaked like pellets to further soften them. Horses which tend to be a bit thin often do well on extruded feeds because the carbohydrates in these rations are more easily absorbed.
Goings-On In The Gut
Providing a feed that is "pre-masticated" can be a great help to an older horse, but it doesn't really address the other major digestive problem he may face -- impaired digestive efficiency. Because his gut doesn't function as well as it used to, it doesn't always scavenge and absorb all the nutrients from his feed. That can lead to weight loss and dietary deficiencies. As a result, you might have to provide an older horse with more feed and higher levels of nutrients than he used to receive just to help him maintain condition. Sarah Ralston, VMD, PhD, ACVN, an equine nutritionist, has said that the nutrient requirements of older horses are more like those of a yearling than they are like those of mature horses based on research she has done on older horses.
It has been estimated that horses in their 20s and up may suffer about a 20% reduction in the ability to digest and absorb certain nutrients, although of course that varies from individual to individual. Most of the loss of function seems to occur in the fermentation vat of the large intestine, rather than the small intestine (where car-bohydrates tend to be digested). Studies with other monogastric (one-stomached) mammals suggest that older horses probably experience a decrease in stomach acid and en-zymes, as well as overall decreased motility in the digestive tract.
We don't know everything about how gut function changes with age, but it has been fairly well established that three nutrients, in particular, are not digested as well -- fiber, protein, and phosphorus. Ralston, who has done several studies on geriatric horses, first noted this effect with a herd of horses aged 20-plus she studied in the 1980s. However, she says that when she re-examined the issue in 1996 with another herd of mares over 20, she found that their ability to absorb protein and phosphorus was less compromised than in the previous herd. "Old horses foaled after the advent of (the deworming medication) ivermectin -- which was introduced in the 1970s -- don't seem to be as bad with respect to the absorption of protein and phosphorus," she says. "My hypothesis is that use of more effective deworming medications means that these horses have less gut damage."
Ralston still recommends that horses over 20 which are not able to maintain their weight on their regular rations and do no have other medical problems be given a diet with a slightly increased level of protein -- about 14%, compared to 10%-12% for younger, mature horses. She also suggests that you decrease the level of indigestible fiber in the diet, and ensure that the ration contains about 0.45% phosphorus. The calcium level in the ration should be between 0.6% and 1.0%, the lower the better, but always higher than the phosphorus.
Interestingly, calcium absorption is not affected by age -- calcium is absorbed in the small intestine, while phosphorus is absorbed in the large intestine. That can make ration balancing a little tricky, since calcium and phosphorus often are found in supplements together. This is one instance where the addition of a high-phosphorus feed, such as wheat or rice bran, might be useful if you're providing a lot of calcium already, however alfalfa hay should not be fed to an aged horse. The rule of thumb about calcium:phosphorus ratios in younger horses holds true for older horses -- you want to provide at least as much calcium as phosphorus, never the other way around. In the case of an equine senior citizen, you want to watch that phosphorus levels don't drop too low.
One way to provide all of these dietary changes is to switch to a commercial grain ration designed specifically for "senior" horses. Now widely available, the main difference in these feeds relative to non-"senior" feeds, according to Ralston, is higher levels of protein and phosphorus and better digestibility. Most are pelleted for easy digestibility, and some are formulated with a softer-than-usual texture, which makes chewing less arduous. "If your horses are doing okay on a regular feed, don't bother switching," Ralston says. "But if they're losing weight, it's time to consider it."
One nutrient that seems to be absorbed just fine by older horses is fat, and that's a major plus, because fat provides a lot of dietary energy (pound for pound, fat provides almost 2 1/2 times as much digestible energy as carbohydrates). What's more, the liquid format of vegetable oils provides no chewing challenges for a geriatric horse; you can even top-dress oil (up to about 1 1/2 cups a day for an average-sized horse) on a pelleted ration to soften the pellets and provide concentrated energy at the same time. If you substitute fat for a good portion of your horse's grain intake, keep in mind that you'll no longer be providing the same level of protein that the grain would have provided. In that case, you might need to add a higher-protein legume hay to the diet, or an easily chewed protein supplement such as soybean meal, to achieve that overall level of 14% protein.
With regard to trace minerals, such as manganese, zinc, copper, iron, iodine, cobalt, and selenium, we don't really know much about what goes on in the gut of an older horse.
"The bottom line is that no work has been done on the absorption of trace minerals (in geriatrics)," says Ralston.
Nor are we clear on all the details of the levels of absorption of macrominerals -- sulfur, potassium, and magnesium, in particular.
We do know a little bit about vitamin absorption in older horses, and it looks like supplemental levels of the B vitamins and vitamin C might help. Ordinarily, horses get all the B vitamins they need from the beneficial fiber-digesting bacteria that inhabit their guts; these microscopic allies manufacture B vitamins as a byproduct of their metabolism. In a horse with compromised digestive function, it's likely that the "gut bugs" aren't working at peak efficiency either. Since B vitamins are involved in the chemical pathways that help the horse process proteins, carbohydrates, and fats, it's helpful to add some to the diet of a geriatric in the hope of boosting his overall digestive function. One of the simplest ways to do that is to feed a probiotic, such as yeast culture, which is a good source of B vitamins.
As for vitamin C, it's ordinarily manufactured in the liver (humans are actually one of the only species that needs to extract vitamin C from the diet). As Ralston notes, "We found that old horses frequently have low levels of vitamin C in the bloodstream. It's often associated with pituitary dysfunction (Cushing's disease), a fairly common condition in geriatrics. Horses over 20 that have had pituitary dysfunction and reduced indices of immunity seemed to produce a better immune response to vaccinations when they were given 10 grams of ascorbic acid powder (vitamin C) twice a day; that's for an average 1,000 pound horse. It also seems useful for horses with chronic infections, and those undergoing periods of stress. It's one of those things that won't hurt, and might help."
If your horse suffers from one of the not uncommon ailments of old age, his dietary concerns might be quite different than we've just discussed. For instance, if he suffers from liver failure (characterized by weight loss, loss of appetite, lethargy, irritability, and jaundice -- a yellowing of the mucous membranes and the whites of the eyes), he won't be able to tolerate high levels of either fat or protein in his diet. He'll need increased levels of carbohydrates in his diet to help him maintain healthy blood glucose levels, and because his liver won't be synthesizing vitamins B and C, he'll need supplemental levels of those nutrients, too. A low-protein grass hay, possibly supplemented with beet pulp, is the best choice for fiber.
In contrast, a horse with kidney failure has a low tolerance for calcium. Unlike most animals, horses excrete excess calcium in their urine, not their manure. When the kidneys cease to function properly, that mineral can build up and cause painful kidney or bladder stones. So, if your horse has kidney problems, he should be placed on a diet with no more than 0.45% calcium -- which means you should avoid legume hays and beet pulp. Protein and phosphorus should be reduced, contrary to the usual recommendations for older horses.
Of course, with older horses often leading surprisingly active lives, you'll also want to take into account the amount of work your horse is doing when you formulate his ration. If he's still in moderate or heavy work, he'll need an increased amount of calories to fuel his performance. If he (or she) is being used for breeding, that will affect your formulations, too. Older mares which are nursing foals, in particular, will need an energy-dense diet so that they don't waste away in the process of raising a foal. Your own careful scrutiny of your horse's condition will be your best indicator of whether his diet is appropriate.
Since your older horse is probably a long-time friend, you should notice changes quickly. Work closely with your veterinarian to monitor his health. You can't keep him going forever, but chances are, he'll have many happy years yet, aided by proper nutrition.
About the Author
Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.
POLL: Tack Shopping Choices