Nutritional supplements have been designed specifically to boost equine performance-but the jury is still out as to their overall effectivenessFood is fuel. No one questions that without good feed in sufficient quantity, a Thoroughbred athlete cannot achieve full potential. But beyond the basics of calories and protein levels, horsemen search for ways to give their horses an extra edge.
Several nutritional supplements currently on the market purport to boost performance by making energy production more efficient at the cellular level. The theory is that if you can delay the point at which the horse's cells switch from producing energy aerobically (with oxygen) to producing it anaerobically (without oxygen), the horse should be able to run longer at top speed.

A short course in biochem
In very simple terms, energy is produced at the cellular level by chemical processes which take apart molecules of glucose or fat, then kick the end products into an ongoing chain of energy-producing reactions known as the Krebs cycle. Various vitamins, enzymes, and fatty acids assist along the way.
The Krebs cycle produces energy, carbon dioxide, and water. When the horse's muscles do not have enough oxygen, the Krebs cycle does not work. Instead, the end products of fat and glucose breakdown go into a fermentation cycle that produces energy and lactic acid.
Lactic acid buildup in muscles produces fatigue and soreness, so the horse slows down instead of driving for the wire. The old-fashioned way to delay the onset of fatigue is to condition the horse's heart, lungs, and muscles to work more efficiently through a specific training program. Can nutritional changes speed up or enhance that process?

Booster rockets
The thinking behind several supplements said to improve athletic performance is that the nutrients they supply somehow give a boost to the Krebs cycle and therefore delay the point at which the horse switches from aerobic to anaerobic energy production.
Some of these supplements were first used by human athletes before being touted as stamina-builders for Thoroughbreds. In the 1960s, the Russians reported that a formula they called "calcium pangamate" enhanced athletic performance. Earlier researchers had called a similar substance "vitamin B-15" or "pangamic acid."
FoodScience Corporation of Essex Junction, Vermont, studied this Russian product in the early 1970s and concluded that the ingredient that gave an athletic boost was N (N-dimethylglycine or DMG), a substance found naturally in small amounts in grains and other foods. FoodScience first began selling a DMG formula for the human market. After an FDA challenge in the late 1970s determined that if DMG was mixed with other substances it would be classified as an unapproved food additive, FoodScience began selling a pure form of DMG for food use. DMG for equine use is sold by FoodScience subsidiary Vetri-Science Laboratories.
Human athletes first flocked to buy DMG when Dr. Thomas Pipes at the Institute of Human Fitness reported that a double-blind comparison of 12 male track athletes showed that those receiving DMG could run 24% longer before reaching the point of exhaustion. Later, studies by Dr. Jerzy Meduski at the University of California indicated that DMG reduced lactic acid buildup in laboratory animals under stress.
Research studies on how DMG affects equine performance provide a mixed picture. A study of of 20 racing Standardbreds using a Vetri-Science product (no longer marketed) that combined DMG with other vitamins and minerals indicated that the horses had lower blood lactate levels and appeared to their trainers to be more "aggressive." Another study by Texas researchers concluded that when a group of six Thoroughbreds was fed DMG, they ran faster with reduced blood lactate levels compared to their performance at the same heart rate without DMG supplementation. However, Australian researchers reporting in Veterinary Record found DMG produced no significant affect on lactic acid production in horses when they conducted a treadmill test.
Vita-Flex Nutrition Company of Staten Island, New York, produces the supplement Lactanase, which combines a number of B vitamins with several fatty acids. Vita-Flex literature notes that these nutrients are necessary to help bridge the gap between glucose and fat breakdown processes and the Krebs cycle. The assumption is that additional amounts of these nutrients will help delay lactic acid production.
To test that assumption, Dr. Joe Pagan and associates of Kentucky Equine Research in Versailles, Kentucky, conducted a treadmill test using four conditioned Thoroughbreds who were already receiving diets with adequate amounts of B vitamins. The test was done in a "switchback" pattern so that all horses were both test horses and control horses at some point in the study to eliminate any training effect. They found no difference in the onset of blood lactate levels between the control and test horses.
Like DMG, coenzyme Q10 came on the equine sports scene after being discovered by human athletes. And like DMG, it occurs naturally in some foods, including cereals, and is involved in energy production at the cellular level. Human athletes have taken it to enhance cardiovascular function and to increase their energy level, but a study of 16 Thoroughbreds by researchers from Washington State University and San Luis Rey Equine Clinic to see if coenzyme Q10 affected blood lactate levels or heart rates during treadmill tests concluded there was no significant affect.
Manufacturers admit that the primary evidence that these nutritional supplements can boost horse performance remains anecdotal. While some horsemen dismiss them, others swear by them.

What's going on?
Dr. Pagan notes that relying on anecdotal evidence rather than controlled scientific experiments is inconclusive since it is hard to determine the exact relationship between cause and effect. The positive effects claimed from feeding a nutritional supplement may be due to the fact that it supplies some vitamin, enzyme, or other nutrient element that the horse lacked without necessarily exhibiting symptoms of deficiency.
The observed effects also may be due to a simultaneous change in the horse's environment or training regime rather than the change in the feed tub. Even controlled scientific studies must be carefully designed to eliminate the possibility of a "training effect" on the horses in the study, Pagan points out.
Pagan also notes that great care must be taken in extrapolating data. Blood lactate levels, for example, are not the same as lactic acid levels in the muscles. Treadmill tests do not precisely simulate racing conditions.
Other researchers are cautious about making inferences about potential effects of oral supplements on horses from information based on human subjects and many laboratory animals. The differences in the digestive tracts, they say, make direct comparisons somewhat invalid.
There may also be biochemical interactions going on that are still not understood. One biochemical interaction, for example, that can clearly affect performance is the practice (largely illegal) of administering large doses of highly alkaline sodium bicarbonate to horses before racing. By raising the horse's blood pH, the "milkshake" draws lactic acid out of the muscles as the horse's body struggles to bring its fluids back to a neutral state. There may be other chemical interactions occurring which are simply not recognized yet.

Putting fat on the fire
One area which offers promise as a nutritive way to boost performance is feeding fat. While fat may be anathema to human athletes, Pagan and others are finding that it may be good for performance horses. Horses whose diets have a higher ratio of fat to carbohydrate than horses who have traditionally been fed appear to become more efficient at completely using up their glucose stores before lactic acid production begins.
Texas A & M nutritionist Dr. Gary Potter has found that when up to 10% of a horse's carbohydrate grain ration is replaced with fat, the horse uses the fat for energy first and builds up reserves of glycogen to call upon when anaerobic energy production kicks in. Potter's work leads him to believe that lactic acid buildup may not be the only factor in muscle fatigue-a lack of glycogen stores may be responsible as well.
The bottom line is that, biochemically speaking, there are still more questions than answers when it comes to feeding for speed. As equine researchers continue to probe for definitive scientific data on how modifications in traditional equine diets can improve athletic performance, the best bet is still to start with a quality animal, then condition it to maximize its aerobic performance at the combination of speed and distance the trainer feels is ideal for that animal.
Put another way, no one is yet selling a feed product that substitutes for a good horseman's good judgment.