- Aug 1, 2005
The first concern when analyzing a performance horse's ration is making sure there are enough calories for basic maintenance needs as well as the added energy requirements of high-level exercise, explains Amy Gill, PhD. An independent nutrition consultant based in Frankfort, Ky., Gill has worked with such equine feed companies as Cargill Animal Nutrition (Nutrena) and Alltech, Inc., as well as individual farms.
For horses, calorie intake is measured in megacalories (Mcals) of digestible energy. Digestible energy (DE) is literally the amount of energy in the diet that is absorbed by the horse, says Joe Pagan, PhD. Pagan is president of Kentucky Equine Research, which was recently named the official nutritionist of the U.S. Equestrian Federation and which has supplied equine feed to the last two Olympics.
"The driving force behind performance is the conversion of chemically bound energy from feed into mechanical energy for muscular movement," says Pagan. In short, as the level or intensity of performance increases, so does the horse's energy requirement. (See The National Research Council's recommendations for daily caloric intake based on performance intensity on page 66.)
How does that translate to actual feed amounts? That depends on the energy content of the horse's ration. For instance, a horse eating only good-quality grass hay with a DE content of 0.85 Mcal per pound would need more than 19 pounds of hay per day to fulfill his maintenance requirement of 16.4 Mcal per day. A horse in high-intensity work would need almost 40 pounds of that hay to meet his DE requirement of 32.8 Mcal per day--a quantity not even the most eager eater is likely to pack away.
So, while forage should always be the basic foundation of any given horse's diet, it's obvious that, as Pagan says, "Forage alone is too dilute to meet the high- performance horse's calorie requirements. You need something with more calories per pound."
It Takes a Variety
To meet that need, says Gill, you need to complement the horse's grass and hay intake with a concentrate. Pagan recommends products containing a mixture of energy sources, a strategy increasingly followed by today's feed manufacturers. Starch, fat, and fermentable (or soluble) fiber are the sources typically used.
Starch--Traditionally, horse owners and feed manufacturers have used starch-rich cereal grains, such as oats and corn, to provide added calories, says Pagan. But that practice has increasingly fallen into disfavor as research has shown that too much starch can cause health problems. In a worst-case scenario, the small intestine can be overloaded, ultimately leading to the release of endotoxins into the bloodstream and potentially colic or laminitis, says Pagan. In addition, notes Gill, some horses have intense reactions to starch, as the digestion process creates a spike in blood glucose and insulin levels that can lead to excitability.
Fat--Over the past decade, fat has taken the spotlight as a way to add calories without the problems of starch. "Fat is extremely well-digested by the horse, and it doesn't cause the rise in blood glucose," says Gill. Fat is also an energy-dense nutrient, with one pound packing as many calories as three pounds of oats or five to six pounds of hay. However, too much dietary fat (more than 1 gram per kilogram of body weight) can actually inhibit the storage of muscle glycogen, a primary fuel for the horse during strenuous exercise, explains Pagan. Typical performance horses need between 7-10% fat in their diets.
Fermentable fiber--The most recent development in providing energy to the equine athlete tosses fermentable fiber into the blend. Fermentable fibers include beet pulp and soy hulls, both of which, says Pagan, are considered "super fibers" because they are higher in energy density than hay and can provide the horse with 90% of the calories he'd get from grain, without the starch-related drawbacks.
"Fermentable fibers are lower in energy density than grain, but fat is higher," explains Pagan. "When you mix the two, you essentially get the same calories as from the grain you withdrew. It's about balance."
Besides exercise intensity, the type of exercise also affects an equine athlete's dietary needs. Equine performance events fall into two general categories: Aerobic and anaerobic.
Aerobic events involve moderate levels of exertion and relatively slow speeds over extended periods of time. Endurance riding is a perfect example. Aerobic exercise primarily uses oxygen to convert stored fuel into energy in a process called oxidation. Body fat, which can only be metabolized aerobically, is used efficiently during aerobic exercise, says Pagan. However, he adds, horses participating in aerobic activities also can convert muscle glycogen for energy, particularly during faster or more intense segments of exercise when fat mobilization is too slow to meet energy demands.
Anaerobic events involve high rates of speed for shorter durations, such as sprint racing. Instead of oxidation, anaerobic exercise primarily uses glycolysis to convert muscle glycogen (from carbohydrates) into energy in a process called oxidation. However, the horse cannot rely on glycolysis for too long, because the process leads to accumulation of lactic acid, which in turn leads to fatigue, explains Pagan.
In reality, says Gill, "All types of exercise have at least some aerobic component, even if it's just warm up and warm down. So it makes good sense to have high-level performance horses well adapted to fat, so utilization of this substrate is preferential when the potential to use it is an option."
The longer the horse can use fat as an energy source, Gill adds, the more glycogen he can reserve, so the longer he'll be able to perform before fatigue sets in. The good news is that fat is considered the horse's largest "fuel tank," adds Pagan, since it can be stored easily in large quantities.
After fat, muscle glycogen is the horse's next-largest fuel tank, followed by blood glucose. Another byproduct of starch digestion, blood glucose can be stored as glycogen in the liver, and the muscles can use it as a source of energy, says Pagan. However, he adds, there isn't much of it, and the horse's nervous system relies on it for proper function. So tapping this tank for energy can lead to neural fatigue.
The bottom line in feeding is to fill all of the horse's gas tanks using a mix of energy sources so the horse has plentiful reserves to pull from during exercise. In particular, you want to top off the fuels he'll use most efficiently based on the intensity and duration of exercise he'll face, says Pagan. And that's where your particular feeding program will need to be personalized for your horse's activity.
Protein Pros and Pitfalls
Often, human athletes pour on the protein for a performance boost, but for horses, it's far less of a concern. As Pagan explains, "The predominant role of protein is as a building block for more protein, such as muscle. In a performance horse, the end product is locomotion." For that, you need energy, and protein is an inefficient source.
Protein is considered an "expensive" energy source because the conversion process taxes the horse's system. Excess protein can lead to high levels of urea, which, when excreted in the urine, is converted to ammonia by bacteria in the stall bedding and floor. Too much protein also causes the horse to drink more water. Combined, these factors mean that a horse on a high-protein diet will urinate more, creating more ammonia in his environment. For a stabled horse, that can spell respiratory distress.
That said, a high-performance horse does need more protein than a lower-level
competitor. But while his caloric requirement might double over maintenance levels, his protein needs go up just 30%, notes Pagan. And that's a figure typically met by the increase in overall feed (calorie) intake.
Pagan also notes that total grams of protein are what count, not percent or concentration. For instance, he explains, if you use a 10% protein feed, and you go from feeding five pounds per day to feeding 10 pounds, you've doubled the horse's total protein intake without changing the percent of protein in his diet. It's that total figure you need to evaluate to make sure you're not overdoing protein portions.
In addition, Gill points out that a protein's amino acid profile makes a difference. "You can actually feed a very low-protein feed and still have good performance if you add limiting amino acids--lysine, methionine, threonine--to the ration," she says.
E is for Antioxidant
Once you've met your horse's energy and protein needs, you need to ensure he gets a balanced ration of essential vitamins and minerals, says Gill. "They play a role in every biochemical reaction in the horse," she says.
Most of today's concentrates handle that balancing task for you. Still, for a high-performance horse, you might want to supplement with antioxidants, such as vitamin E, selenium, and vitamin C.
"When an animal has aerobic metabolism, a lot of times there are end products of this oxidation, called free radicals, that damage cell membranes. Those are kept in check by antioxidants," Pagan explains.
Electrolytes--sodium, chloride, and potassium--are also a consideration for horses in hard work. Horses lose significant amounts of electrolytes, particularly salt, in their sweat, and they sweat a lot. Pagan notes that data collected from the top three eventing teams during the Atlanta Olympics showed that, on average, horses lost more than 15 liters of sweat on speed-and-endurance day alone.
"Because sweat loss isn't necessarily the same for every intensity of work, you can't add electrolytes to the feed," says Pagan. Instead, you'll need to replace lost electrolytes on an as-needed basis, except, of course, for providing free access to salt.
Many other extras come blended into feeds or available as additives, notes Gill. These can range from limiting amino acids to probiotics to joint supplements. Of the latter, Gill says, "In high-level performance horses, joint wear and tear is inevitable. Therefore, using the supplements for joint lubrication is just good maintenance."
Another class of additives is known as ergogenic aids and includes creatine and dimethylglycine. "They are supposed to make the horse generate more energy or generate energy more efficiently," Pagan explains. "Most of those have not stood up to scientific scrutiny."
Part of the reason, he explains, is that these products, which come largely from human nutrition, must address a bottleneck in the energy-generation process. Horses and humans don't face the same bottlenecks, so the same products might not assist both species. What's more, adds Pagan, horses are already highly efficient at generating energy, so these aids don't give them an added edge.
Bottom Line: Focus on Forage
When it comes to mixing, measuring, and formulating an ideal feed for performance horses, says Gill, "There is no recipe for optimum." Pagan agrees, noting that past studies have indicated huge variations between individual horses performing at the same level of the same discipline. KER, he adds, will be conducting its own study of the seven USEF high-performance disciplines to see what competitors are actually feeding their horses and if there are any notable commonalities.
Meanwhile, Gill and Pagan advise owners of equine athletes to put money first into good-quality forage, the bedrock of a sound feeding program. Then supplement with a concentrate that provides a mixture of energy sources and is fortified to meet vitamin and mineral needs. Supplement with electrolytes as needed and with other products designed for your horse's individual issues (such as poor hoof quality, ulcers, or joint issues).
"Then," sums up Pagan, "you're probably there."
NRC Daily Digestible Energy (DE) Recommendations
|Maintenance||Not in work||0%||16.4 Mcal|
|Light||Pleasure or equitation||25%||20.5 Mcal|
|Moderate||Reining, cutting, jumping||50%||24.6 Mcal|
|Intense||Polo, racing, eventing||100%||32.8 Mcal|
SOURCE: NUTRIENT REQUIREMENTS OF HORSES, NATIONAL RESEARCH COUNCIL, 1989.
WEIGHT WORRIES: Is the Plan Working?
One way to assess whether your feeding plan is working is to watch your horse's weight. Amy Gill, PhD, an independent nutrition consultant based in Frankfort, Ky., and Joe Pagan, PhD, president of Kentucky Equine Research, both recommend assessing an equine athlete's body condition every two weeks. Use the standard body scoring scale (The Ohio State University offers an explanation at http://ohioline.osu.edu/b762/b762_2.html) and a weight tape or a livestock scale. "Know how the horse looks when he's right, so that if he gains 50 pounds or loses 50 pounds, you know you're headed in a bad direction," says Gill.
If you need to adjust your horse's diet to counter unwanted weight loss, Gill advises first increasing forage (she prefers a legume-grass hay mix). Start by adding about two pounds per day, which equals about 3,500 calories. If you don't see signs of improvement in about two weeks, consider increasing concentrate by about a pound per day.
If your horse has weight to lose, cut back on concentrate quantities. "You can go to a protein, vitamin, and mineral concentrate if your horse truly needs to limit all calories from carbohydrates and fat," says Gill. Remember to make all feed changes gradually so you don't upset your horse's delicate digestive system.
In addition, notes Gill, consider your management strategies any time your horse loses weight. Stress is a prime contributor to weight loss, she notes, but something as simple as daily turnout can counter it.
"I have seen many a fine horse fed the greatest feed in the world, but they're mismanaged and stressed, and they look terrible," she says. "And I've seen horses on mediocre feed, and they look great because they're under good management and not feeling stress."--Sushil Dulai Wenholz
WHEN YOU FEED IS IMPORTANT: Time to Eat
For equine athletes, the timing of meals matters for two reasons:
Glucose spikes--Feeding carbohydrates causes an increase in blood glucose, which triggers insulin to activate and store the glucose, says Joe Pagan, PhD, president of Kentucky Equine Research. During this storage mode, insulin will also inhibit the conversion of fat to energy. If you exercise your horse at this time, he'll rely largely on blood glucose--the smallest fuel tank--for energy.
"The studies we've done show that if you wait four to five hours after feeding, the horse is more efficient at burning fat," says Pagan. However, he adds, endurance riders who feed during a ride--say, at a vet stop--can avoid insulin interference if they begin exercising again within 30 minutes of feeding. "The worst case is if you feed, wait two hours, and exercise while the insulin is at peak level," Pagan says.
Ballast--A heavy meal can literally weigh your horse down, hampering his performance ability, says Amy Gill, PhD, an independent nutrition consultant based in Frankfort, Ky. She recommends feeding smaller amounts at a time on performance day, and particularly as competition time approaches. She advises against skipping a meal entirely, since this can lead to ulcers and might leave the horse distracted by hunger and not focused on the task at hand.
About the Author
Sushil Dulai Wenholz is a free-lance writer based in Lakewood, Colo. Her work appears in a number of leading equine publications, and she has earned awards from the American Horse Publications and the Western Fairs Association.
POLL: Managing Working Horses