Monday, October 30, 2000

Beating the Metabolic Pull. Part I - Hydration - Susan Garlinghouse

Reprinted from Endurance News, June 2000
Susan Garlinghouse, MS

My belief has always been that if a rider understands some of the why in nutrition and physiology, then it is much easier to understand the how in making well-informed decisions during and between rides. This article is the first in a three-part series explaining a little about the way things work in an exercising horse, along with suggestions on how to apply this knowledge for better metabolic integrity and performance.

Whether your goal is to race at FEI levels, top ten or just get back into base camp before the barbecue is all gone, the common denominator is that first you have to finish with a horse that is fit to continue. You do not need an advanced degree to recognize the metabolically fit horse---he has good gut sounds, is eating, drinking, is well hydrated, bright and alert. Most of us have also seen the other end of the scale---the deflated horse with an IV running into his neck, that the treatment vet is hovering over, that is on his way to a clinic. The difference between the fit to continue horse and the treated horse depends largely on three primary metabolic factors---hydration, gut motility and energy balance. The first two are so closely related as to be almost the same issue and are by far the most critical factors in maintaining metabolic integrity. The third factor, energy balance, has become a hot topic and can certainly make the difference between a win and a middle of the pack finish. However, the amount of rocket fuel on board is not going to help if your horse is dehydrated, colicking and already in trouble. If you remember anything from these articles, remember the order of priorities---hydration and motility first, and then energy balance. Assuming your horse is conditioned for the job at hand, and you have paid attention to maintaining hydration and motility during every stage of the ride, you will find your horse has better performance, recoveries and stamina, long before you start considering, "how do I increase his energy?"

This first article covers hydration, which is much more involved than just letting the horse drink at every water stop, and remembering to carry a sponge. What exactly does water do in the body, anyway? For the endurance horse, one of the most critical roles is the removal of excess heat during exercise. During a fifty-mile ride in ambient temperatures, the average horse will produce enough heat to melt a 150-pound block of ice, and then bring that water to a boil. If that heat is not removed, the internal body temperature will quickly rise high enough to literally cook the entire body. Evaporative cooling via sweat production and respiration accounts for the majority of heat dissipation during exercise. Horses that are dehydrated progressively lose their ability to produce sweat, a condition called anhidrosis, resulting in loss of cooling and a concurrent rise in body temperatures. As the body dehydrates and blood loses plasma volume and fluidity, the cardiovascular system becomes less efficient at transporting oxygen and other resources throughout the body. The heart rate increases to compensate, so that a horse that canters easily at 130 beats per minute when fully hydrated may have a heart rate of 20-30 beats higher when dehydrated, simply due to the extra work of pumping less fluid blood. Not only does this result in slower recoveries, but it also has a significant effect on the efficiency of muscle function. To maintain the same intensity of work, the horse will rely more and more heavily on anaerobic metabolism, contributing to faster fatigue and greater incidence of metabolic disease, such as colic or tying-up. As effort increases and efficiency decreases, the body responds as though to an emergency (which, in fact, it is), and begins to shunt blood flow away from less-vital organs, such as the gastroin testinal tract, in order to maintain maximum circulation to heart, lungs, muscles and central nervous system. As blood flow decreases to the digestive tract, gut motility slows and may stop entirely, leading to colic until blood flow and motility are restored.

Progressive dehydration also affects the normal functioning of the "thirst center" in the central nervous system. Thus, dehydrated horses badly in need of fluids may entirely lose interest in drinking voluntarily. If you know your horse has been working and sweating hard throughout the day, and yet is not drinking, do not assume he doesn`t need water. In fact, he may be approaching a metabolic crisis if not resolved quickly. Don`t make the mistake of thinking, "he knows best what he needs"---use your head to make the right decisions on his behalf.

During a hot and strenuous ride, horses can lose from 1.5 - 4 gallons of water per hour in the form of sweat. Over the course of a 50-mile ride, this can often add up to ten (or more) gallons of fluid lost solely through sweat production. Research conducted by Gary Carlson at UC Davis indicates that the average Tevis horse experiences a net loss of almost five gallons of fluid between the start and finish (equivalent to approximately 4% of body weight in a 900 - 1000 pound horse). Losses of over 12 gallons have been measured, representing 10% of the body weight. Keep in mind these numbers represent the fluids that remain unreplenished in the equine body, after the horse has presumably had ample opportunity to drink throughout the day. These results indicate that even under ideal circumstances, horses may not be able to drink enough water to replenish the fluids lost through sweat production, resulting in progressive dehydration.

It has been estimated that dehydration losses of as little as 3-4% (that is, 3-4% of body weight has been lost in the form of fluid) have an adverse effect on performance, even though outward clinical signs may not be readily apparent. Horses experiencing an 8% dehydration have a capillary refill time of 2-3 seconds, poor skin tenting, dry mucous membranes, dry feces (and, therefore, are at greater risk of colic) and generally a high, hanging heart rate. A horse at 10% dehydration is in serious trouble, requiring extreme veterinary intervention, and at 12%, the horse is close to imminent death. Skin tenting alone is a relatively inaccurate method of determining extent of dehydration, and often lags behind changes in true hydration status. Therefore, along with the ride veterinarian, you must consider all metabolic factors in evaluating your horse, including mucous membranes, gut motility, heart rate, capillary refill time, attitude and way of going.

What is the difference between a clinically normal horse with 4% dehydration and one in metabolic distress at 8% dehydration? Less than five gallons of fluid in the body can make the difference between completion and a metabolic crisis. So--- your horse is already drinking at every puddle and bucket, you have finally mastered that flying sponge trick, your crew is waiting with plenty of cool water for washing, and you dutifully clip his winter hair every year. What else can you do to improve his hydration status?

One of the easiest ways to prepare for good hydration on Saturday is to maximize forage intake the week before. Forages take several days to reach the hindgut, so that Thursday`s hay is in the cecum and large colon on Saturday. For reference, the foregut consists of (in order) the stomach and small intestine, while the hindgut consists of the cecum, colon and rectum. Fiber both encourages water intake and absorbs and holds water as it moves through the digestive tract. Although 90% of the water will have already been absorbed prior to reaching the hindgut, several gallons are still present and available as the hay moves through the system on Saturday. This provides a significant extra reservoir of fluid and electrolytes to draw upon during exercise-induced dehydration. Recent research has indicated that feeding one of the soluble "super-fibers", such as soaked beet pulp, along with hay, further increases this fluid reservoir. This extra water alone may make all the difference between Completion and Trouble. Make sure that the horse has hay available during the trailer ride to base camp, as well as immediately upon arriving and unloading. Adequate fiber intake the night before, as well as a dose of electrolytes, will trigger thirst responses and drinking throughout the night to ensure the horse starts fully hydrated.

The timing of meals fed before and during a ride also has an effect on hydration. Many horses are still provided with a large "breakfast" before the start, little or nothing until the lunch stop when another large meal is provided, and then little or nothing again until the finish. Studies have demonstrated that such feeding practices (more than 4-5 pounds of any type of feed, spaced more than 2-3 hours apart) results in a large fluid shift from the plasma volume (the fluid portion of blood) into the digestive tract. These fluids are used to provide saliva and other gastric juices needed to process the large meal. In a 1000-pound horse, these fluid shifts may equal 4-5 gallons of fluid, resulting in a 15-24% decrease in total plasma volume. Don`t worry about the exact numbers, just think which is easier for the heart to circulate---thin, fluid blood, or thick "sludge"? While this fluid moves back into the plasma volume within a few hours, the net result is a transient dehydration that can significantly affect performance until the condition corrects itself. In a backyard horse standing around doing nothing, the effect is relatively unimportant---to an endurance horse that covers many miles in those few hours, the effect can make a significant difference.

To avoid this fluid shift, simply avoid feeding large meals only at vet checks---help your horse be a "nibbler" instead of a "feast-eater" during endurance rides. The same amount of food, fed in small, frequent meals every hour or two---instead of intermittent feasts--- avoids these fluid shifts entirely, and yet still provides the same total nutrition. Make an effort to provide small amounts of food in between vet checks---a baggie of hay or grain in a cantle bag, or a few minutes of grazing along the trail. If you know you will be doing some footwork in the next few miles out of a vet check, carry along a thin flake of hay and hand it out as you jog along. Practicing eating along the trail at home will make it easier for your horse to do so during a ride---and there are few tricks your horse will learn faster than that you want him to eat along the trail! Although opportunity differs for every rider depending on the goals for the day, the point is to examine your riding plan and make an effort to provide small, frequent meals whenever possible, avoiding the intermittent feast. Those few extra minutes spent along the trail will be worth the effort in metabolic health and performance.

The rule of "small and frequent" also applies to anything provided in an oral syringe. While fluid shifts are not as large or dramatic, any concentrated source of salt or sugar draws fluid inward until the diluted solution is reabsorbed into the bloodstream a relatively short time later. To minimize the effect, any oral syringing should be broken up into smaller doses---better eight 2-ounce doses than two eight-ounce doses! Make every effort to only syringe after the horse has already had a drink (preferably immediately afterwards), as the less dilution required from plasma volume, the better. Not only will plasma volume be spared, but also absorption of the electrolytes into the system will be more efficient and thus more available during exercise. Pre-loading electrolytes several hours before the start and throughout the day not only avoids progressive electrolyte depletion, but also triggers a complex endocrine response in the kidneys and central nervous system to encourage early drinking. Once absorbed, the body does not store excess electrolytes, so pre-loading should be limited to the night before and several hours before the start. Pre-loading for days and days before a ride does no harm, but is simply a waste, as the kidneys have long since flushed the excess out in the urine as soon as current needs have been met. While salt does trigger a thirst response, and can be used to encourage drinking during a ride, the response is not an immediate one. Use this as an early strategy to maintain a metabolic edge throughout the day---if you wait until the horse is already dehydrated and in a crisis state, the best you can hope for is damage control. Recognize the difference between a horse that is not drinking because he doesn`t like what is being offered, and one in a metabolic emergency. In many instances, all the horse may need is a few extra minutes to recover, eat some green grass, hay or mash, and then will drink normally. If the horse is not drinking when you know he should be, is uninterested in food, recovering poorly, acts dull or colicky, or is otherwise exhibiting signs of exhausted horse syndrome, do not attempt to magically fix the situation with a large oral dose of electrolytes alone. At this point, it`s entirely possible to make the situation worse instead of better. Realize that the horse is in a crisis and seek veterinary help immediately---although correcting the electrolyte imbalance is an immediate priority, administration with fluids via intravenous or nasogastric tube into the stomach, rather than oral syringing, may be required to prevent further deterioration of the situation.

Although not as prevalent as in past years, it is still common to see endurance horses being fed rations which are well in excess of protein requirements, especially in the West, where good alfalfa is cheap and plentiful. While many horses have and do compete successfully on high-alfalfa rations, this too has an effect on hydration status and should be a consideration in your metabolic strategy plan. Horses that compete well on high-alfalfa rations are most likely doing well in spite of the high dietary protein, not because of it---undoubtedly a testament to the many other management, conditioning and riding factors that a smart owner puts into a successful ride. For every horse that wins a ride while consuming a high-alfalfa ration, there are undoubtedly many others that could have finished, placed higher, or earned better vet scores by simply decreasing the dietary protein consumed. This conclusion is supported by Dr. Sarah Ralston`s work at Rutgers University, which suggests the incidence of metabolic pulls increase as dietary protein levels significantly exceed requirements.

Mature performance horses only require 8-10% crude protein in their diet, and these needs do not significantly increase with the demands of endurance conditioning. Good-quality grass hay or pasture easily provides these protein requirements regardless of the level of performance. If you are in doubt about the quality of forage, a few pounds of a 12-14% grain mix from a reputable company ensures adequate protein without supplying excess. Supplying "extra" in the form of alfalfa or high-protein supplements, such as Calf-Manna, to "support muscle development", is neither required nor beneficial.

A high protein ration`s effect on hydration is based upon its inherent nitrogen content. Once protein requirements have been met, the body utilizes excess protein for energy production. The amino acid molecule is snipped apart and the carbon backbone sent into energy-producing pathways, while the remaining nitrogen atom is discarded. Nitrogen is first degraded to ammonia and then to urea, which is subsequently filtered out by the kidneys and excreted in the urine. Both ammonia and urea are toxic substances, therefore urine production to remove them from circulation takes priority over water conserving responses during exercise. The net effect is that horses consuming high-protein rations have increased urine production and higher water requirements simply to clear the body of an avoidable waste product. In horses living in box stalls (not uncommon in highly developed urban areas), the increased ammonia and urine production can lead to greater incidence of upper respiratory irritation, as well as poorer hoof wall and sole quality. During a ride, when water intake may already not be enough to keep up with loss, the additional loss of water through increased urination is an added contribution to potential dehydration.

While excess protein does contribute to energy production, the pathway is a relatively inefficient one, as protein metabolism produces 3-6 times more waste heat than does the utilization of an equivalent amount of carbohydrates or fat. In cold climates, this heat production from excess protein can be used to help maintain body temperature, especially during the off-season. However, during hot weather and prolonged exercise, this excess heat must be removed from the body via the same cooling mechanisms as heat from exercising muscles---sweat production and respiration. During intense exercise in hot or humid conditions, the net effect is a greater heat load to dissipate, increased fluid and electrolyte losses, and yet another contributing factor to potential dehydration. Does this mean you should not feed alfalfa at all during endurance rides? Not necessarily. Alfalfa contains high levels of both calcium and potassium, and small amounts throughout a ride can help offset electrolyte deficits. However, a few pounds at vet checks are sufficient, especially if you are otherwise providing electrolyte supplementation, and more alfalfa is not necessarily better! If your horse is being picky at a stop, and refuses anything but alfalfa at vet checks, better to let him eat more alfalfa than he really needs than to not eat anything at all. Ideally, however, provide limited amounts of alfalfa, while offering other lower protein feeds such as grass hay, beet pulp or grain-based mash. At home (if alfalfa is fed at all), limit intake to 25% of the forage ration, and never more than 50%. Again, while many horses continue to compete successfully on high-alfalfa rations, its effects on hydration status should be a consideration in your management plan.

To summarize the main strategies included in this article:

# Maximize forage intake for several days before the ride, including the use of "super fibers", such as beet pulp.
# Pre-load with electrolytes the night before and several hours prior to the start.
# Provide small, frequent meals every hour or two along the trail by carrying along a few pounds of feed, or by intermittent grazing.
# Anything provided in a syringe should be provided in small doses at frequent intervals, preferably after a drink.
# Provide a ration adequate, but not excessive, in dietary protein by limiting alfalfa and other high protein feeds.

Beating the Metabolic Pull. Part III - Energy Balance - Susan Garlinghouse

In this final article in the series, we`ll discuss the possible ways to increase energy during a ride without jeopardizing the overall health of the horse. At the risk of becoming tiresome, remember the order of priorities in protecting metabolic integrity--- hydration, gut motility; and only then, look to increase energy balance. Luckily, these issues are often so closely interrelated that attending to one issue often benefits all three.

Before discussing specific strategies, it`s helpful to have a brief review of the energy substrates available to endurance horses (or any other equine athlete). There are essentially three "fuels" utilized during exercise; phosphocreatine, glucose and fats. All three function via different pathways to produce the same end product, adenosine triphosphate (ATP), the actual energy source that drives muscular contraction.

Of these three fuels, phosphocreatine is of the least importance to the endurance horse, and only worthy of brief mention. Think of PC as the "starter fuel" in the muscle cell---it is what will provide immediate energy for the first few seconds of exercise, until other fuel sources arrive in greater quantities for long-term exercise demands.

Glucose is intermediate in both its supply and speed of response during exercise. When molecules of readily-available glucose are stored in plant material, it is referred to as starch, and when stored in the animal body, as glycogen. Because the storage of glycogen in the body requires both water and space, relatively little is stored in the body. Fats, on the other hand, are far more efficiently stored and so can be accumulated almost without limit (as some of us have discovered after the holidays). The advantage of utilizing glucose as an energy source is that it is more quickly available than are fats, and while it is most efficiently metabolized in the presence of oxygen, it does not require oxygen to produce energy. During intense exercise, the cardiovascular system of heart and lungs may be unable to supply sufficient oxygen to individual muscle cells. Under those circumstances, energy can continue to be produced for a short period by utilizing those pathways that do not require oxygen. These pathways are referred to as anaerobic, and utilizing them during exercise is referred to as passing an anaerobic threshold. Utilizing these pathways results in the accumulation of the metabolic by-product lactic acid, and thus, the "burn" felt in overworked muscles. This pathway is not meant for long-term exercise, as the accumulation of lactic acid and rapid depletion of cellular glucose stores quickly contributes to muscular fatigue. Therefore, the primary advantage to glucose as an energy source is its versatility in either the presence or absence of oxygen, and its speed in being quickly available on demand.

Fats are the fuel of greatest importance to the endurance athlete. While their utilization absolutely requires the presence of oxygen, and is not as quickly available as glucose or phosphocreatine, its supply within the body is almost unlimited in any horse in reasonable body condition. It has been calculated that the average 1100 pound horse has only 45 calories available within body stores in the form of phosphocreatine; approximately 18,000 calories available in the form of glycogen; and approximately 153,000 in the form of fats. When you consider that an average horse carrying a lightweight rider will utilize more than 19,000 calories during a flat fifty-mile ride at an average speed of 8 mph, it becomes apparent that body stores of glycogen alone are insufficient to fuel the exercise demands of the day.

The disadvantages of fats as a fuel source are that they absolutely require the ongoing presence of oxygen within the cells to produce energy, and they are the slowest of the three sources to become available after the onset of exercise. A third feature, which may at times become a distinct disadvantage, is that while glycogen may be utilized by itself without any other substrate, fats require a small but critical amount of glycogen to produce energy---hence the saying, "fats burn on the flame of glycogen". To use an old analogy---think of glycogen as a smallish pile of fast-burning kindling, and fats as heavy, thick logs. While the logs will supply far more total heat, they cannot burn well without kindling. On the other hand, while kindling will burn rapidly and well, its relatively small supply will soon run out, leaving you without the wherewithal to burn the logs. Therefore, the key element in energy management is to rely on fats as the primary fuel source, and to conserve the limited supply of glycogen for "kindling" and for carefully planned spurts of anaerobic activity which may be necessary to reach your riding goals for the day.

Complex system that it is, the body is well adapted to utilizing the fuel most suited to the exercise at hand. At rest and during moderate exercise, with plenty of oxygen available, the body will utilize primarily fats, the fuel in greatest supply, with just enough glycogen being used as kindling to produce energy at its highest efficiency. As the intensity of exercise increases, as during a tough hill climb or a prolonged sprint, oxygen supplies may become insufficient and energy utilization shifts from the oxygen-using pathways, to those which do not require oxygen. Fats are utilized less and less, while glycogen becomes more and more important---so that at maximum intensity, the reliance on glycogen is approaching 100%. At this intensity of exercise, glycogen stores are rapidly depleted, and the accumulation of lactic acid greatly increased. As complete glycogen repletion may take several days, as well as the complete removal of accumulated lactic acid, an extreme exercise bout of this intensity is best left for either the flat-track racehorses, or if necessary, at the very end of an endurance ride. Once the system is pushed to this level of exhaustion, you had better be close to packing it in for the day!

Given the energetics of endurance horse metabolism, how do we put this to use during the riding season? One of the first ways is to utilize a high-fat diet. Although still the subject of research and heated debate, studies in exercising horses have demonstrated several clear metabolic benefits for endurance horses. Its most obvious benefit is that fats are the most concentrated source of calories available, and therefore of the most use in adding calories to an existing ration. Up to several cups of any type of good-quality vegetable oil (with the exception of linseed), or crystallized fat supplements such as FatPak, provide enough additional calories for most horses to maintain a good body condition.

Fats in the diet also have the benefit of decreasing heat production during digestion, thus lowering the heat which must be dissipated through sweat production by as much as 14%. Remember that proteins produce from 3-6 times the amount of metabolic waste heat as do carbohydrates or fats. By supplying calories in the form of fat, instead of protein, the amount of metabolic heat that must be dissipated is decreased, thereby helping to product hydration throughout the day.

A further benefit is that horses adapted to a high-fat ration over an eleven week period (and it appears to take this long to reap the full effect) demonstrate a glycogen-sparing effect. Essentially, the body becomes more efficient at utilizing the fuel source in greatest supply (fats), and therefore is able to conserve the fuel supply most likely to run out (glucose). By doing so, horses under laboratory conditions were able to exercise for a longer period of time at a lower heart rate, with less lactic acid accumulation, than did horses maintained on a strictly high-grain or high-protein ration.

Does this mean that fats should be fed during an endurance ride? Common sense would say yes, but in reality, the answer is no. Remember that a horse in good body condition---ribs easily felt but not seen, and without jutting hip or pinbones---already has a plentiful supply of body fats onboard to fuel the day`s work, even during 100-mile or multi-day rides. Remember also from lprevious discussions in this series that protecting gut motility is a higher priority than is energy balance, and providing bulkier feeds will maintain blood flow to the gut far better than will fats. Therefore, while adapting horses to a high fat ration between rides is an excellent strategy, withdraw the fats the night before in order to encourage forage intake. Utilize rice bran (which has a 20% fat content) as a condiment in mashes to increase palatability, rather than the majority of the meal. After the ride is over, return to including fats in the regular ration. Skipping fats for a few days during a multi-day will not put you back at ground zero in that eleven week adaptation period---simply start the fats again once you arrive back home.

Bottom line---strategies to maintain energy during a ride should be aimed towards protecting and maintaining an ample supply of glycogen, the kindling to burn all those available fats. At the risk of sounding preachy, one of the most obvious elements of your plan is to arrive with a well-conditioned horse. A large part of the physiological response to conditioning is the increase in efficiency of the muscular and cardiovascular system--- not only at delivering oxygen, but also storing glycogen and removing waste products. A horse with borderline conditioning is much more likely to slip over the anaerobic threshold, and use up available glycogen much more quickly than if he were truly fit for the job at hand.

In order to help protect glycogen stores, the first strategy is to start with a full load onboard. "Glycogen loading" has been explored and utilized in human marathon athletes, but seems to be relatively ineffective (and at times, risky) in horses, possibly because they are already evolved to store relatively large amounts of glycogen in muscle and liver tissue, compared to the inferior human athlete. Simply making sure that the glycogen stores are full, without attempting to overfill, is more than adequate. This can be done by slightly increasing the grain ration several days before the ride---an extra two or three pounds spread over several days is sufficient. If your horse is already consuming significant quantities of grain as part of his regular diet, then adding more is probably unnecessary. Decreasing the intensity of exercise for a day or two before the ride, as normally happens anyway, is enough. If it is part of your normal routine to go for a short ride after arriving at base camp, you can certainly continue to do so, but now is not the time to go haring off across the wilderness in a five mile sprint. An easy ride to loosen muscles will keep the glycogen stores where they belong in preparation for tomorrow.

Offering one more moderate meal of grain the evening before the start, along with plenty of free-choice hay and ideally, soaked beet pulp, will "top up" the onboard glycogen stores. Again, just a pound or two of grain will suffice---in order to protect hydration and motility first, the consumption of plenty of hay during the night will do more to produce a successful ride than will "just a little extra" grain.

Many riders are in the habit of providing a grain meal to their horses first thing in the morning, in order to have "plenty of energy during the day". Remember that wheat bran counts more as a grain than as a forage, although less so than do oats, corn or barley. The theory in feeding "breakfast" is that by maintaining high plasma glucose levels, glycogen stores will be spared for use later in the day. Again, common sense would say this is a good thing to do, but in reality, grain in the morning works against the production of energy. The starch content within grain is quickly broken down to simple sugars in the small intestine prior to absorption. As blood glucose rises, insulin is released from the pancreas to regulate and move the glucose into storage. The steeper the rise in glucose, the greater the insulin release and the more quickly glucose is moved from circulation and into storage. Plasma glucose levels quickly drop, not only back to baseline, but below previous levels. The net effect is that for several hours after a grain meal of several pounds or more, plasma glucose levels will quickly spike, and then decrease sharply, making glucose relatively unavailable as a fuel source until the system stabilizes. This phenomenon is called the hypoglycemic rebound effect.

At the same time, high plasma glucose and insulin levels have the effect of decreasing fat utilization, so that not only is glucose relatively unavailable, but so are fats. The result is a decrease in endurance and speed for several hours, directly opposite to the desired effect. By feeding the last grain meal no sooner than four to five hours before exercise begins, you are giving the body a chance to digest, absorb and stabilize glucose and insulin levels well before exercise demands begin. Not only will glucose be available in ample quantities, but so will fats very soon thereafter. Remember that excitement releases adrenaline, and adrenaline releases glucose. Most endurance horses will have no trouble whatsoever generating sufficient glucose during the first loop!

Can this hypoglycemic rebound effect occur during the ride as well? Absolutely. Research has indicated that any grain-based meal of several pounds or more, whether the grain consists of corn, barley, oats or sweet feed, has the same effect. Remember also from previous articles that large meals, spaced more than a few hours apart, also has a detrimental effect on fluid balance---a second reason to avoid large, sporadically spaced meals during ride day.

To avoid these effects, remember the rule of small and frequent---rather than grain only at vet checks, carry a small baggie or two of grain between vet checks to offer every hour or so. This not only will avoid swings in insulin and fluid balance, but will also provide a small, steady source of glucose throughout the day without decreasing the utilization of fats. The net effect is increased energy and better performance without jeopardizing the overall metabolic health of the horse. Remember that providing bulk as well throughout the day is the higher priority in maintaining hydration and motility, so include fresh green grass, hay or soaked beet pulp mash as well throughout the day as your ride plan allows.

A recent and controversial innovation is the use of carbohydrate supplements that can be syringed at intervals during a ride as a replacement or supplement for grain. To date, no published research studies have thoroughly investigated its use or effects on the endurance horse, and the only existing information is anecdotal. The theory behind its use is the same as that for grain, and the same caveats apply. Too much of any carbohydrate source at any one time can cause fluid shifts, hypoglycemic rebound, as well as the potential for colic or laminitis if greatly overused in a metabolically stressed horse. Poor results are by far most likely to result if carbohydrates are used as a replacement for proper and long-term conditioning, or in an effort to obtain performance beyond the current capabilities of the horse. Carbohydrates of any type will not only will not turn an exhausted, dehydrated horse into a winner, it can potentially turn a possible completion into a metabolic disaster if every other detail discussed in this series hasn`t first been seen to. Those who have done their conditioning homework and use carbohydrates thoughtfully in conjunction with a realistic and sensible ride plan, are by far to be most likely to garner a demonstrable benefit as "icing on the cake" without risk to the metabolic whole.

To summarize the main strategies in this article:

# Remember that glycogen is the fuel in shortest supply, and plan your ride strategy to conserve glycogen, staying primarily below the anaerobic threshold, while relying on fats as the primary fuel.
# Maintain your horse on a high-fat ration in between rides, but avoid feeding fats on ride day.
# Provide a "full tank" of glycogen by increasing the grain ration slightly for several days before the ride, with the last meal being no closer than 4-5 hours before the start.
# Provide small, frequent amounts of grain along the trail every hour or two, avoiding large, sporadic meals, along with bulkier forages.
# If used at all, utilize carbohydrate supplements as "icing on the cake", never as a replacement for doing your homework.

Beating the Metabolic Pull. Part II - Gut Motility - Susan Garlinghouse

Reprinted from Endurance News, July 2000
Susan Garlinghouse, MS

In the second article of this series, factors affecting gut motility and how they help maintain metabolic integrity will be discussed. Remember that last month`s article introduced a list of priorities in avoiding a metabolic crisis during an endurance ride---first, pay attention to hydration; second, to gut motility, a very closely related issue; and as a distant third, attend to maintaining energy balance. Maintaining the first two factors exerts such a positive effect on the metabolic whole that overall performance and recovery will be improved even before energy balance is addressed. Later strategies to increase energy throughout the ride then become icing on the cake, while still maintaining strong metabolic scores during vet checks.

The term "gut motility" refers to the normal sounds of digestion audible via stethoscope through the abdominal wall, and provides a good indication of the stress level being experienced by the horse. Under normal circumstances, the gastrointestinal tract of the horse generally maintains a slow, constant churning (or peristalsis) as food is digested and moves through the system. Horses and other herbivores evolved to a diet of forages maintain this churning action not only after a meal, but continuously over hours and days as the high fiber portions are fermented and slowly broken down and absorbed into the bloodstream. Control of the digestive process is maintained by circulating hormones, and is subject to a priority system when the body is under stress, as during strenous exercise. As the exertion level increases beyond that which is easily maintained, the body assumes that the animal is under attack and is fleeing for its life---physiologically, it does not make the distinction between a life-threatening emergency and simply a prolonged, over-enthusiastic gallop. Complex hormonal signals adjust the distribution of blood flow to maximally support the cardiovascular and muscular systems to continue its "escape"; maintain support to the vital organs such as heart and brain; and temporarily diverts blood flow away from those systems uninvolved in the "fight or flight" response, such as the digestive tract. As a result, blood flow to the hind gut gradually decreases as stress and the intensity of exercise increases, and motility concurrently slows or stops. If motility is decreased for long enough, colic eventually results as gas and fluids begin to accumulate, causing distention and pain. Although there are many causes of colic, slow gut sounds at a vet check are almost always related to decreased blood flow to the intestinal tract, which in turn is almost always related to the body being pushed beyond it current capacity and into a state of physiological emergency.

Remember from the previous article that dehydration has a profound effect on efficiency of the cardiovascular system. As plasma volume decreases, blood thickens and becomes less fluid, requiring the heart to work harder to transport oxygen and other resources throughout the body. Likewise, as plasma electrolyte supplies become depleted, the efficiency of cellular function, including muscle, also decreases. The net result is that a dehydrated horse`s body more readily goes into a physiological state of emergency, diverting blood flow away from the digestive tract, than does one that is fully hydrated. A vicious cycle is created in that dehydration and electrolyte imbalance directly causes a decrease in intestinal motility, while the loss in motility impairs the horse`s ability to absorb the fluid and electrolytes needed to correct the situation. A critical point to understand that even though a ride`s terrain, temperature and speed may not differ greatly from training rides at home, minor variations in conditions can cause a cascade of physiological effects that have a significant impact on the metabolic well-being of the horse. Never make the mistake of thinking that because your horse easily exercises at a certain speed at home without turning a hair, that he will automatically do just as well at that speed during competition. He might, but then he might not! Sometimes even such minor details as level of excitement (of both horse and rider) can affect the body`s response to fatigue and stress. Especially in relatively inexperienced endurance horses, continually assess your horse and adjust to meet the change.

As with many other issues in endurance riding, there are many shades of gray in determining the degree of metabolic trouble. Few riders take the time to check gut sounds out on the trail, but carrying a stethoscope just in case is always a good idea. Changes in attitude, lack of interest in eating or drinking and signs of dehydration warrant a quick check in all four quadrants on both sides. While fully accurate interpretation of gut sounds is not easily learned without veterinary training, simply being familiar with your horse`s normal frequency and characteristics will help you identify brewing trouble out on the trail if a veterinarian is not readily available.

What to do if faced with potential colic either at or between vet checks? Recognize that poor gut sounds are an indication that the horse is exercising beyond his current capacity, creating a progressive state of physiological stress. If you are out on the trail and moving towards a vet check, the obvious first answer is to slow down. Decreasing the demand on the cardiovascular and muscular systems will allow the body to recover and reduce the emergency status it is responding to. As the body moves back towards recovery, blood diversion away from the digestive tract will eventually begin to reverse itself and intestinal activity will improve as blood flow returns. Helping the horse to recover does not necessarily mean stopping entirely to rest. In fact, gut activity will be improved if you keep moving steadily. Research has indicated that blood flow to the digestive system, and therefore maximum efficiency of the digestive process, occurs when the horse is exercising at approximately 20% of his maximum aerobic capacity. For most fit horses carrying a rider, this is usually somewhere between a brisk walk and an easy jog. As an added bonus, continuing low-level exercise flushes waste products such as lactic acid from the muscles more efficiently than occurs at rest, so the entire body benefits and recovers more quickly, while still maintaining forward progress towards a check and veterinary help.

By adding bulk to a slow digestive tract, additional hormonal signals are released that move the digestive tract higher on the priority list in line for blood flow, thereby increasing intestinal activity. While the GI system `s demands will not displace those of the cardiovascular or muscular system during strenuous exercise, once the body recovers from emergency status, blood flow and motility will more rapidly return if feed is in the stomach. The bulkier the food item, the more the stomach walls are stretched, and the more motilin (a hormone which triggers peristalsis) is released. Therefore, whether at a check or out on the trail, encourage continuous eating, preferably of moist, bulky forages such as green grass, wet hay or soaked beet pulp. Avoid concentrates such as grain, which can exacerbate colic and laminitis if the problem persists beyond a temporary situation. Remember from last month that even before a crisis state is reached, allowing for small, frequent meals along the trail benefits hydration status as well. Since gut motility is so closely related to hydration, continuous nibbling along the trail therefore provide advantages in both areas.

It is a common misconception that wheat bran mashes possess laxative qualities to provide bulk and avoid impaction during endurance rides. They do---for the rider! Humans and horses have vastly different digestive systems and while bran (of any type) is poorly digested by the monogastric species such as humans, dogs and pigs, thereby providing bulk as it passes through the GI tract, this is not the case with herbivores, such as horse, cattle or sheep. Horses are able to easily digest the fiber in bran via microbial fermentation in the cecum and large colon, and thus little or no additional bulk is produced to promote motility. Clinical research has demonstrated that horses fed almost 50% of their total ration in the form of wheat bran did not produce greater quantities of fecal material, or produce feces of greater moisture content. So while sloppy bran mashes are an acceptable feed at rides, and a good way to introduce electrolytes, additional moisture and other feeds during a stop, they should be viewed as a grain product, not as a significant source of fiber to promote motility.

In the interest of providing feed with maximum bulk to promote motility, pay attention to particle size of ride-day forages. Remember that motility factors are triggered as the result of stretching stomach walls, and that maximum stretch yields maximum motility. A pound of long-stem hay yields the same total nutrition as a pound of pelleted hay, but the volume of long-stem hay is significantly greater and therefore it`s potential ability to stretch stomach walls, even after chewing. Even if you normally feed pelleted hay at home (and it is recommended that at least 50% of the hay ration be in the form of pasture or long-stem hay to maintain gut integrity), always provide long-stem hay at rides. Due to the relatively slow digestive process of horses, always provide plenty of hay for several days before the ride, including free-choice hay throughout the night before. If you provide wet mashes at stops, consider soaked beet pulp mashes instead of wheat bran. Beet pulp absorbs tremendous amounts of water during soaking and provides significant moisture as well as bulk. Additional grain products such as wheat bran, sweet feed or other concoctions can be added to increase palatability and provide additional energy.

Although added fat as an energy source seems like a good common-sense idea during rides, you`re probably better off not providing significant fats on ride day. Fats do indeed provide the primary source of energy during endurance exercise, but if the horse is in reasonable body condition---fit and muscular without staring ribs or hipbones---then he already has sufficient body fats on board to provide sufficient fatty acids throughout the day. Adding additional fats during the ride, therefore, is providing a fuel source already in good supply, at the expense of attending to other critical issues. Because fat is such a concentrated energy source, a meal high in fats tends to decrease total intake, thereby decreasing the total bulk needed to maintain gut motility. For this reason, vegetable oil should not be added to ride-day mashes, and any added rice bran to increase palatability should be provided as a condiment, rather than the majority of the meal. Focus on green grass, long-stem hay and well-soaked beet pulp to provide bulk throughout the day, with additional grain sources to provide energy only if motility is being maintained.

To summarize the main strategies in this article:

Recognize that poor motility is an indication of blood flow diversion away from the digestive tract as the result of stress, and reduce the intensity of exercise to allow blood flow to return. Maximum blood flow to the GI tract occurs at approximately 20% of maximum aerobic capacity. Remember the strong relationship between hydration and motility, and maintain the latter by protecting the former. Move the GI tract higher on the blood flow priority list by adding bulk to the stomach to trigger release of endocrine motility factors and promote peristalsis. Utilize long-stem hays, green grass and soaked beet pulp rather than wheat bran or high-fat feeds to maintain intestinal activity.

Steph and Khruschev`s 2000 WEC Experience - Steph Teeter

Khruschev and I were part of the 2000 World Endurance Championship event, representing the US in Compiegne, France. Two years of focus and preparation, all for ONE ride! I enjoyed every minute of the process and have no regrets, only thanks - to friends and family that helped along the way, and tolerated the obsession without complaint. Our story isn`t one of glory or tremendous success, but of persistance and teamwork. We didn`t do the race I had hoped for and trained for, but we had an amazing ride - the USET support staff gave 100% and was first class. We finished 32nd out of 150 starters - respectable, but not reflective of Khruschev`s ability and level of training. But this story is not about placement, it is about teamwork, and about finishing. My crew - my friends and family - were unbelievable, I can never thank them enough, and we couldn`t have done it without them. And Khruschev is a one-in-a-million horse.

As I write this, I`m flying over the Pacific Ocean, headed home. Khruschev is also in the air, on a different plane. I wonder if he`s thinking about the past few weeks, replaying the events, re-riding the course. Horse memories. Most likely he`s just munching his hay, exchanging occasional reassurances with his travelling buddies, Sam and Ramsz, and thinking about his next meal. The `here and now` of being a horse.

We had our share of challenges during the past few weeks. None of the challenges we faced were what we had trained for, what we had anticipated. But Every one of the challenges taught me some valuable lessons - stay flexible, stay tough, trust your horse (he will always give you everything he has), count on your family and true friends (they will always be there for you) and never ever give up. It ain`t over `till it`s over!

Khruschev caught a nasty cold while being shipped to California and developed a persistent cough. With the help of Nancy Elliot (USET team vet) and the constant support and concern of the friends I made during our stay he got through it. He was back to normal and the cough finally subsided in time for shipping. Hang in there. Then the trail gave out from under us during a training ride in the steep hills of coastal California. Khruschev slid down the ravine while I managed to bail off over his head. He waited for me at the bottom, and beyond odds managed to scramble and lunge back up the wash and onto the trail. His left hind and left front legs were bloody but there was no serious damage. The timing wasn`t too good though - USET was doing a final soundness evaluation the following day, only sound horses would be shipped over seas. The next day his hind leg was bruised and hot to the touch where he had scraped it. He was trotted straight out of his pen without a warm up - perfectly sound, out, back, circles left, circles right. Hang in there ... we`re still in the game.

We arrived in France on Saturday and settled in at the stables north of Compiegne. Beautiful old barn tucked in the Compiegne Forest, full of gorgeous Celle Francais and Spanish Warmblood horses, and friendly and helpful folks. We spent the first few days hand walking the horses, settling into a routine, grazing them in the field out back. There were paddocks available for turn-out, but the ground was wet and soggy from the unseasonal rains and we were afraid of what it would do to their feet going from dry to wet in such a short time so we tried to limit their time outside. The long days confined to stalls were hard on some of the horses. Khruschev is pretty much `ok` wherever he is though - just keeps eating and drinking and being a horse. But there was trouble brewing with his feet. We had our first formal trot-out evaluation on Tuesday (Aug9). The first few steps he took were off. My heart sank, and you could hear a pin drop. Uh oh. (Hang in there)The next 17 days were a constant emotional roller coaster. We pulled his shoes the next day, his feet had become extremely soft from time in the soggy pasture, the soles had turned crumbly, he had a deep corn in the left inside heel, a bruise near the toe. Both feet seemed sore, but he was most uncomfortable with the left front. Nancy pared the feet down and dug out the corn which was starting to abcess. She packed his feet and we gave him 24 hours with his feet packed and wrapped. Our farriers weren`t due to arrive for another 10 days. Darolyn and Cowboy said the Brazilians were somewhere in Compiegne with their farrier so the search began. The following evening we took the packing off of his feet and the Brazilian farrier trimmed them (btw - the Brazilians were great!!) - Cowboy had extra easyboots and we were thinking these could get us by until the farriers arrived. This plan backfired big time. The easyboots were not quite large enough and we had to really crank to get them on - the result was that the next day Khruschev was lamer, sorer than before. Now his heel bulbs were bruised and sore too! His feet had become so soft and sensitive that they bruised from the easyboot straps. I felt so bad for him - it was beginning to feel like the harder I tried, the worse it got. (hang in there)

By now John and Destry had arrived, and Susie and Lari were coming soon so I had plenty of moral support and also help keeping his feet iced, trying to ease the discomfort. everybody at the barn - riders, crew,support staff- was incredibly supportive and helpful.) The saga continued for the next two weeks, we tried three different shoings (thanks Ernie, Jaye, Brazilians) - one day he seemed better, the next day sore again. (hang in there) It was a fairly consitent pattern - the first few steps were the worst, but once he took more steps and warmed up he was better. He felt good when I rode him, but after he stood for a while, the first few steps were uncomfortable - better again once he warmed into it. We tried to keep a minimum level of fitness with longing and walking, but the best thing for him was rest and time (something that was running out).

Friday (Aug 25) arrived and all of the US horses were evaluated that morning for soundness before the official vetting in. Khruschev wasn`t perfect, but Rick gave me the ok to give it a try. So we presented to the officials - After the first trot-out there was some mumbling and head shaking and we were sent to another lane for further evaluation. Another trot - still some inconsistency. One more time .... about the same, but they gave us a thumbs up to start. The official smiled at me as we walked out - "maybe he`ll warm out of it - good luck Khruschev". It was a wonderful, friendly gesture. Hang in there.

We went back to the barn, I felt like we had been given a gift just being able to start, and yet another chance. And I knew that it wasn`t time to give up yet. I started looking for Jaye Perry (one of the USET team farriers), somehow hoping there was still something he could do to make Khruschev comfortable. Jaye was not to be found, but I was told he had left earlier in the day, searching for a farrier supply store. We spent the afternoon getting ready for the ride - John, Destry, Suzie, Lari and Carol worked non-stop preparing everything we would need for the ride. They kept the spirits high and acted like everything was going to be fine. I was the most dejected I had felt during the past two weeks. My wonderful horse was not himself, we might get through the first loop, at least we could start the race, but this was the 11th hour and I was running out of optimisim. Jaye showed up at the barn around 7pm that evening. I asked him if there was anything else he could do - any more rabbits to pull out of his hat? He smiled and said "where do you think I`ve been all this time?" Over an hour later Khruschev had his final (4th) shoing since we had arrived. We walked him around. Jaye looked satisfied and said just put him in his stall, he`ll be fine. Hang in there. I didn`t even trot him out, had no idea if he would trot sound then, or even in the morning. But I couldn`t bring myself to find out at that point.

That night during dinner and into the next morning I felt incredibly calm - almost numb. During all the excitement of getting ready in the dark, the electricity and anticipation that others were feeling, I was calm and quiet. I had already received one `gift`, just being able to start and at least do the first 20 mile loop. Nothing more could be done now in preparation. My crew was totally prepared and I knew they would take care of everything. The only thing I had left to do was ride our best ride - mile by mile. I knew this was not the race we had trained for - our challenge was not the sand, the speed, the heat and humidity. I had to keep him sound and comfortable. We joined the other 150 riders in the warm up area - just climbing on his back I could feel the transormation in his attitude - he was ready for a race! But I still hadn`t trotted him! We walked for about 15 minutes and I finally mustered the courage to trot - perfect!! He felt solid and absolutely wonderful. As soon as the race started I could feel Khruschev go `yes! finally! now let`s go do our job!`. He flew out into the dark with the others, even threw in a few good bucks - it was exhillarating and very emotional.

My plan was to ride mile by mile constantly gauging our progress by his comfort level. Cruise when the footing was soft and take it easy on pavement and cobbles. I felt it was best to start cooling him down a mile from the vet check - have him pulsed down and ready to present as soon as we got there - no standing around, just keep him moving. We got to the first hold just as the other US riders were leaving. I had walked him in the last mile - trotting intermittently - he seemed great. He was down as soon as we got in, went right to the vet. John and Suzie took him and I lost them in the crowd - we had started, we had gone 20 miles, more than I had expected during the last 2 weeks. Would we do another loop??? Yes! He passed - CRI was 52/48 and he got an A on gait! Whoop and holler... and then down to business. Next task - loop 2. Let`s see if we can squeeze in 14 more miles.

And so it went.... all day long. Each loop was a gift. Each hold was a joyous occasion. Khruschev`s crew (John & Destry (my son) , Suzie Hayes, Lari Shea, Carol Andrews & Linda Voigt) was excellent - fast, efficient, encouraging, and Fun! They worked non-stop, feeding, icing Khruschev`s feet, preparing electrolytes, making sure I was eating and drinking and laughing. And Khruschev was the model horse to crew for - was pulsed down when he arrived, never stopped eating, drank well, allowed himself to be fussed over and was just plain ol` happy.

We rode steady all day. Fast trot and canter in the woods and soft trails, easy easy on the rocky stuff. It got incredibly humid during the afternoon - hot and stifling. We rode alone all day (after the first wild loop) and he never asked to quit. I slowed somewhat during the worst of the heat, but he handled it well. There were zillions of US volunteers out on the trail at the crew points. Friendly, willing, ready to do whatever we needed - pour water, give electrolytes, mash, whatever. It was a great boost to our spirits to have them out there.

The final hold was at Pierrefonds, with the castle looming in the background. It was magical for us. By then the only other US rider left was Connie, and she and Smoke were doing great. We only had a 30 minute hold (at 88 miles) and they had all the horses do an exit CRI. I was pretty anxious ... 12 miles to go, is he still ok? I was too anxious to eat much during the hold - but we still managed to spend the time laughing and having fun. Final CRI and trot out - 60/52 and A for gait - unbelievable!! We left the last hold with everybody hooting and hollering - a real boost for our spirits. The sun was setting as we rode through the Pierrefonde Castle - . , the stones and turrets were glowing orange from the sun, the windows reflecting the sunset. I imagined Khruschev in armor, and horses of another era..

One more loop - Khruschev felt incredibly strong and I was tempted to let him pick up the pace and to move up in our placing - many tired horses had left before us. But I played it safe - with only one other US completion, I felt that it was too great a risk to change our mode of caution. We rode the last 6 miles in the dark - trotting when we could, being extra cautious in the rocks, and steadily moving on. We reached the final pit crew area, one mile before the finish, and the enthusiasm and hollering as we left were more than we could resist. We flew in the last mile - and came to the finish in a huge extended trot - the stand was full of cheering spectators and as far as Khruschev knew, we had won! (I never told him otherwise.)

The human spirit is indomitable. After the Fort Howes ride in Montana this year, we were having breakfast, sharing the table with the joyful, dancing Canadians. One of them had just finished his first 100 miler, he finished last, just before cut-off time but from the look on his face that morning you knew for certain that he was a winner, his excitement and enthusiam were radiant and infectious. We were laughing about the trials of the trail, being out all night with the coyotes and he grinned - "well you know, AERC`s motto is `To finish is to Win` - I`m a winner, eh?- go motto!"

Steph Teeter