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Here is one I had to copy and paste.  Sorry it is a little long, but good.

Cheryl Winter

Carbohydrates in Performance Horses

The substrates for athletic performance in the horse, the human, the rat,
and the elephant are all the same: carbohydrate-derived, protein-derived or
various forms of fat. That is to say, the horse is not from Mars. The horse
is a mammal, with mammalian energetics. In this regard, there is no need to
reinvent the known science to fit the horse.

The literature suggests that carbohydrate-derived muscle fuels are the
dominant factor in both power production and fatigue resistance, and this
has proven true in practical application, from high speed racehorses to
100-mile endurance horses--just as the literature from human exercise
science has predicted.

Here is an economic paradigm that is reflected, in substance if not scale,
throughout the world of performance horses: The Thoroughbred that
consistently delivers a racing mile in one minute and thirty-seven seconds
is a $30,000  horse. The Thoroughtbred that consistently delivers a 1:33
mile is worth many millions of dollars. In short, improved performance is a
tremendous economic lever in our world, as it is in every athletic endeavor.
Those of us involved in providing support services to the performance horse
world must focus primarily on performance, consistency, and longevity.
Proper use of carbohydrate in the diet can be an extremely productive tool.


Carbohydrate and Fatigue Resistance

In human athletes, muscular fatigue reduces performance in athletes
competing in events lasting from 10 seconds to several hours. The whole
thrust of training and nutritional protocols focuses on reducing or delaying
the onset of fatigue. In performance horses the problem is more severe
because not only does fatigue lose races, but it leads to injury. The
biomechanics of the horse are such that muscle fatigue results in changes in
gait and lower leg posture which in turn predispose the animal to a variety
of career-ending injuries, from bowed tendons and torn suspensories to chips
and fractures and joint deterioration.

For decades it has been thought that the primary culprit in the cause of
fatigue in race horses is lactic acid buildup. It was also thought that
lactic acid production was due to a lack of oxidation potential at the
muscle cell level. Academic research tended to support these conclusions
because elite athletes were shown to have higher lactic acid thresholds
(VLA4) than those with less training or inferior oxidative delivery/uptake.
For decades, then, training protocols and nutritional supplementation--and
even illegal drugging--focused on the oxidative side of the
equation--bigger, more efficient hearts, expanded plasma volume, expanded
capillarization, increased red cell production, increased mitochondrial
density. All of these factors could be manipulated  through sophisticated
conditioning routines and supportive nutrition.

Digging deeper into the substrate aspect of fatigue resistance, we've
recently seen a number of papers that come to similar conclusions as the
following paper.

T Reilly, V Woodbridge
Effects of moderate dietary manipulations on swim performance and on blood
lactate-swimming velocity curves
International Journal of Sports Medicine, 1999, Vol 20, Iss 2, pp 93-97Georg
Thieme Verlag, P O Box 30 11 20, D-70451 Stuttgart, Germany

The results indicate that a moderate reduction in CHO intake alters swimming
performance adversely whereas a moderate elevation in CHO intake above the
normal diet improves performance. The dietary manipulations affected the
response of blood lactate to both submaximal and maximal swimming
velocities. The observations highlight the limitations of applying lactate
response curves to swim training.

The investigators are concerned that a high carbohydrate diet interferes
with their testing for performance capabilities. The athletes fail the VLA4
test but perform better?a ³paradox² to these researchers.  This parallels
our experience on the racetrack with "glycogen loaded" horses.

Seven years ago, I was called in as a consultant to determine the cause of
bad racing performance in a horse named Acey Mack, racing in Portland
Oregon. For several races in a row, at 6 furlongs, this horse would come
around the turn in front only to stop so badly that the horses behind him
had to get out of his way as he backed through them. He'd finish last or
next to last.  An extremely complete diagnostic workup was performed,
including post-race blood analysis, to no avail. Nothing was wrong with this
horse--he wasn't bleeding, had no airway obstructions, no fractures, no
abnormal blood parameters, no heart problems. His immediate post race blood
lactate was 22 mmol and his post race CK was 350.

We ran the horse back one week later, but during that week, we "glycogen
loaded" him--a process that consisted of his normal ration supplemented with
a 4 ounce dose, 3 times a day, of a maltodextrin/chromium polynicotinate
powder over a period of four days, including the next race day. In this
race, he was second by a nose--an estimated performance improvement of 15
lengths according to Daily Racing Form charts. The next week he was second
by a nose again. Then he won four races in a row, racing weekly for the most
part. Blood was sampled immediately post race after the first glycogen
loaded race. CK was 250, lactic acid was "out the roof"--greater than 35
mmol. 

Thus, the "paradox" of no fatigue with very high lactate numbers in the face
of greatly improved performance. We are led to the conclusion that 1) lactic
acid buildup has minimal impact on fatigue, 2) higher levels of stored
muscle glycogen will result in more glycogen being used in a race and result
in higher lactate production, 3) in spite of higher lactate levels, the
extra available substrate results in greatly improved racing performance.

Of course, Acey Mack represents "one-rat research". In the seven intervening
years, several thousand more "rats" have demonstrated decided benefits from
this "glycogen loading" protocol.



A Central Problem

In the early days of our "applied research" on the racetrack using glycogen
loaders we ran into a serious problem. For some reason, unknown to us at the
time, about 10% of the horses we glycogen loaded delivered the very worst
performance of their lives. They ran "flat". Our first guess as to the
etiology of this disastrous result was that something else that was being
given to the horses was reacting poorly with the glycogen loader. There was
no health threat--the horses would come out of their poor races happy and
healthy--and apparently "ready to race again, right now".

The story of how we eventually solved this problem is long and tedious and
full of trial and error--I'll cut to the chase: If, at post time, the
horse's blood glucose is either crashing or at a low point, he will race
"flat"--just not be capable of making competitive racing speeds. The
solution is to ensure that the animal's blood glucose is elevated, and not
crashing, at post time. Two pounds of grain, fed two hours out from post
time, completely eliminates this problem.

Why does this phenomenon occur? We know that it happens with non-glycogen
loaded horses as well. If a trainer's routine is that every horse gets fed
at 11 AM on raceday, and some horses race at 1:00 in the afternoon and
others race at 5 PM, about 10% of those racing later will suffer from the
same "flatness" as do the glycogen loaded horses. The trainer will say, "He
wasn't himself today", or "He just didn't fire". In some stables, this has
led to running glucose response curves on every horse in the stable in order
to determine precisely what the blood glucose will be at post time in the
individual horse. 

It is my unproven theory that at the time the rider pushes the "go" button,
coming out of the starting gate, and demanding a sudden 110% effort,  the
central nervous system takes a quick survey of available survival
fuel--blood glucose. If there is a CNS-perceived blood glucose crisis, then
the CNS inhibits muscle firings. We know that the CNS is capable of this
kind of inhibition--Guezennec (2000) elucidates at least one mechanism. The
factors that trigger this action are yet to be catalogued in the literature.


Loading Versus Supplementation

Some equine events require lower levels of muscular activity and increased
precision in skilled performance (dressage). Others combine skills with
tests of fitness (eventing). Still others demand relatively low level
muscular performance for extended periods of time (endurance). We have found
that a loading protocol used prior to skills competition typically does more
harm than good. The horse has too much energy and makes enthusiastic errors.
But in a 3 day event, beginning an abbreviated loading protocol immediately
after the dressage section should produce a beneficial result as long a
proper timing considerations are observed.

A similar problem is encountered when attempting to glycogen load for
endurance horse competition. In this case, if you begin a 100 mile race with
a very enthusiastic, bursting with energy horse, The horse either goes too
fast or spends a lot of effort fighting with the rider--you soon run into
elevated body temperatures and dehydration--this is the worst possible
scenario for the beginning of a 7 1?2 to 14 hour competition.

We are now supplementing fact-acting carbohydrates all along the way--4
ounces of the same glycogen loader formula mentioned above every 1 1?2 hours,
beginning with one dose 15 minutes before the start of each loop. (An
endurance race might consist of approximately 5 loops of, to round out the
numbers, 20 miles each, with rest periods and veterinary checks between
those loops). Water and electrolytes are also given periodically throughout
the ride. In these contests, a large percentage of the competitors is unable
to finish--many simply "run out of gas" and cannot press on; others run
headlong into severe metabolic distress and must be treated quickly with IV
fluids. Many of these latter are demonstrating very low blood glucose at the
time they are pulled from competition.

Those horses that are properly supplemented with carbohydrates (and
electrolytes and water, of course) tend to be enthusiastic performers to the
end of the contest and pass veterinary checks with ease--barring physical
injury. Those that are improperly supplemented with the loader formula
crash, often sooner than the others that wee not supplemented. Improper
supplementation occurs when the supplement is not fed frequently enough or
when it is stopped halfway through the race for one reason or another. Thus,
if you are going to supplement fast-acting carbohydrate during an endurance
contest, you have to do it frequently and you cannot stop until the contest
has finished. 

So, 4 ounces (128 gm) of maltodextrin/chromium  fed every 1.5 hours (perhaps
as much as 40 ounces in a 100 mile event) is ergogenic in 750 to 1000 lb
horses exercising for hour after hour at heartrates typically ranging
between 115 and 145. Dehydration and hyperthermia are not problems that
these supplemented horses face--again, given proper electrolyte and water
maintenance (hyperhydration in the days leading up to the event also appears
productive). 

Those are the well-documented results from the "coaches and athletes" in the
field. But can we explain why, scientifically? Does the literature offer a
hint as to why a primarily aerobic and fat-based substrate metabolism would
be enhanced by frequent carbohydrate supplementation?

The first thing we see in the literature are numerous studies supporting
both glycogen loading prior to endurance competition and frequent "sports
drink" (water, glucose and electrolytes) intake during competition in human
athletes. These protocols are clearly ergogenic.

Let's look at the available substrates. Muscle glycogen, liver glycogen,
stored intramuscular di- and triglycerides, blood glucose, protein, and
adipose tissue in addition to gut contents of fiber. In comparison to the
energy available from these sources, even 40 ounces of "loader" or lesser
amounts of "sports drink" glucose in human athletes, seems insignificant as
a working substrate. Something else is happening.

One thing we know is happening because of field studies is that the rate and
quantity of loader dosage will maintain an elevated blood glucose throughout
these endurance races. In fact, some tests have shown a continuous rise in
blood glucose as the event grinds on. From the science we know that elevated
glucose means elevated insulin and that in turn results in a decided
inhibition of lipolysis. So, with carbohydrate supplementation, adipose
tissue becomes a less important player in the working substrate mix.

However, the stored muscle fats, the di- and triglycerides, are always
readily available and probably contribute greatly to the exercise energy
pool at these low intensities. And recent science is hinting that these
"fats" are somewhat hybrid in form--not quite true fats, not quite sugars.
But fast-acting, nevertheless.  And I'm old enough to remember the old adage
"fat burns on the flame of glycogen". Meaning that once muscle glycogen is
depleted, the performance is over, no matter how much fat is still
available. And, once blood glucose is gone, the Central Nervous System dies.
Before that happens, though, the CNS will shut down the activities of all
the other organs to preserve fuel for itself--starting with the working
muscles. So the glucose-depleted athlete comes to a near standstill.

We know, too, that part of the ergogenic effect of carbohydrate
supplementation in human athletes is the beneficial effect on "perceived
exertion". That is, the athlete feels better with an elevated blood glucose.
In fact, there is evidence from the higher intensity middle distance events,
5K and 10K runners, that "hitting the wall" of fatigue occurs as
carbohydrate-based substrates are depleted to the extent that the body makes
a concerted attempt to switch substrate metabolism toward fats in an attempt
to allow glycogen/glucose sparing and give the liver time to regenerate
glucose through gluconeogenesis and protein catabolism (blood ammonia levels
track well with this type of fatigue).

Given adequate water and electrolyte intake, if we can maintain elevated
blood glucose during an extended endurance race, we can prevent a "crash" in
performance by maintaining a carbohydrate-driven metabolism.


Safety in Feeding Carbohydrates

To date we have experienced no adverse reactions to sometimes very large
carbohydrate supplementations. No tying up, no colic, no laminitis, no
induced diabetes. We use a longer chain maltodextrin in order to smooth out
the glucose response curves from doses of glycogen loaders. We add chromium
so as to help avoid overloading the insulin system.

We advise our clients to feed normal balanced rations, spread out over
several feedings a day and consisting of a 50-50 concentrate/forage
intake--primarily grass hays for the forage. The highest grain intake I've
observed was 26 pounds of mixed grains a day, spread over five feedings, in
a mare named Stanerra, who won the Japan Cup, among other Grade I stakes.
She consumed a like amount of hay. Her workload was strenuous--up to 15
miles a day.

Our generalized rule as far as daily carbohydrate feeding is concerned is to
"feed the work".  But the daily intake remains constant, with no half-feed
days and full-feed days. We avoid days off, where the horse performs no
exercise, particularly with racing-fit horses. We try to ensure that the
horse either gains or maintains body weight throughout the conditioning and
competition processes. In some stables, the horses are weighed every day.
The recovery/supercompensation  cycle tracks with body weight fluctuations.




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