I dare say that almost every racehorse that leaves the starting gate is dehydrated and in a state of electrolyte imbalance. Dehydration and electrolyte imbalance in the racehorse has often been casually ignored by most trainers, if not out right encouraged in the case of dehydration. Horsemen will often give the traditional IV jug after a race or supplement the feed / water bucket with electrolyte powders of various unknown qualities and quantities, but little else and then mostly after a race. It is a common tradition to take the water bucket out of the stall on race day along with the routine administration of the anti-bleeding diuretic, Lasix, which makes fluid imbalances even more of a problem in racing horses. I will on this page attempt to make some sense out of all of this and bring into this discussion the scientific body of work pioneered by Thomas M. Riddick and Dr. T.C. McDaniel OD on zeta potentials from a medical--physiological point of reference. Zeta potentials are very important to the well being of the racehorse and we will find out why and how to more closely monitor these zeta values in the stressed performance horse on this page.
Lets first establish two "truths' before we do anything else with this discussion. Number one, I think it is universally agreed that a proper electrolyte balance is optimum for a top performance in any athlete, be it two or four legged. So, we will go with the premise that proper electrolyte chemistry levels are to be desired in any racehorse for optimum performance on the track. Number two and here we will encounter some controversy, dehydration is to be avoided and decreases performance levels though one will find a debate on this matter in horse racing. However, there is no such dispute in the realm of human athletics as sports performance scientists agree dehydration is bad. Should there be a difference or are we horsemen ignorant?
As incredible as it might seem, many horsemen feel a dehydrated horse races better. It is standard operating procedure for water buckets to be removed from stalls of horses on race day for 4 hours or more before a race. I know, I was brain washed with this concept as a young man in the sport as an axiom not to be questioned. I didn't until much later in life. Green grass also has traditionally been shunned until after a race perhaps for the same reason of stimulating hydration? And, lastly, most USA racehorses are treated with lasix which really wrings the water out of an organism before a race and is considered a performance enhancer. So what gives?
Lasix (Furosemide) is the drug of choice in the USA for legal pre-race "drugging". It is thought to work in two ways. It reduces (not prevents) bleeding by lowering blood pressure in the horse via dehydration as a treated racehorse can lose any where from 10-15 liters of urine in a few hours of treatment which reflects directly on blood volume. And this is not counting body weight loss from sweat which can be up to 10% of body weight, Instead of the blood pressure being 4x as high as the resting rate during exercise, lasix seems to reduce it to about 3x. It is also thought that such a large volume loss may aid equine race performance by a reduction in body weight (10-20 pounds) by this fluid loss. If this is true, then perhaps we are racing our horses too heavy?
Racehorses need increased blood pressure and a healthy total blood volume for a reason! Jack Keyes in his text, Fluid, Electrolyte, and Acid-Base Regulation, writes: "Any event that reduces blood flow will also reduce the delivery of oxygen. " The 4x pressure is required to push red blood cells through the circulatory system for tissue oxygenation and this is particularly true when one considers that the horse's spleen releases a large volume of red blood cells during exercise. The racehorse also needs a normal blood volume to accommodate the increased red blood cells released by the spleen during a race. It is just a logical deduction to know that if one decreases blood pressure or total blood volume as lasix does, race performance will suffer or worse, sudden death can result. Lasix has often been linked directly to sudden death, but this seems never to be a published reason in sudden deaths seen on the race track in conjunction with bleeding. Weight lifters who are avid lasix abusers consider lasix to be the number one drug for deaths seen in that sport, not anabolic steroids! In 2015, a human study of non-athletes on lasix seemed to point to sudden death in 3.66% (3,455) out of the 94,473. Just imagine how the stress of a race could magnify the lethal effects of lasix in athletic performances if it is that common in ordinary humans! The human medical literature is rift with the subject that lasix can contribute to sudden death while if you read the equine literature, EIPH (bleeding) is the part talked about that can cause direct sudden death in the equine, not lasix, with lasix seemingly being put forth as the savior against bleeding sudden deaths seen on the race track! I think we have a classification problem here of which came first, the chicken or the egg! One of the landmark studies that many articles use to demonstrate how deadly EIPH can be in the racehorse is from 1988 by Gunson et al where he only studied 9 horse deaths and they were all on Lasix! The valid question here is, were the deaths due to EIPH or lasix? I suspect lasix was more of a factor than hemorrhage. It has been my training experience that a bleeding horse will slow down and protect himself, not collapse from death from the simple act of bleeding. Bringing lasix into the equation can bypass this natural response to slow down resulting in the sudden deaths seen in conjunction with EIPH. I wont delve into this further, but just know, I have yet to see any studies that could separate EIPH racehorse sudden deaths from the possibility that these animals deaths were complicated or caused directly by the use of therapeutic lasix before hand. Accordingly, I consider the claim that lasix saves lives bogus to the extreme.
Beyond all of this, the veterinary accepted thought is that EIPH is due to blood vessels bursting from the normal 4X pressures seen at exercise, shouldn't one suspect that the real problem might be the fragility of the circulatory tissue of which there can be many reasons? For example, scurvy, the lack of Vitamin C, is one long time known pathological cause of vein & arteriole fragility resulting in bleeding! Vitamin C can be "used-up" by infections. Perhaps our racehorses are suffering from a localized form of scurvy as I suggest on my EIPH webpage? As usual, modern medicine finds it more commercially viable and easier to treat the symptoms rather than the cause.
It goes without question (among trainers, anyway) that lasix can help reduce racetrack bleeding and that it can improve race performances in some horses, but I think the problem lies in the interpretation of the obvious. Chemically reducing naturally higher exercise blood pressures or body weight is not the answer! There may be other mechanisms for why Lasix is helpful that have been overlooked? As I pointed out on my EIPH webpage, Lasix has been shown to destabilize biofilms with this perhaps being one reason why it improves EIPH cases? In a most recent study (Pagan et al, 2013), six thoroughbreds on a treadmill produced results that showed lasix acted as a blood lactate buffer and delayed oxygen debt. It was theorized that this was mainly due to a reduction in body weight. Another study from the Equine Veterinary Journal (2006) came to similar conclusions that reduction in body weight was a key reason why lasix is performance enhancing. Lastly, an American Journal of Veterinary Research (1990) study also suspected weight loss to be the key factor, but also discovered that Lasix had no value as a preventative for EIPH.
It appears that quick weight loss from Lasix seems to be the culprit to its performance enhancing affects. A famous saying often heard in the shedrow is that "Enough weight can stop a train"! Beyer suggests from his studies that 3.05 pounds equals one length at 6f. Trainers know all too well how important weight is and that is why lighter weights are coveted by them. That is the reason why they love weight allowances and bug boys that can ride lighter! Using lasix to get that weight loss is not the best way to go about it as we will see in the next paragraph. On the balance scales, you may get a degree of performance enhancement from pre-race Lasix, but at what cost, at what negatives? Just imagine how much better a racehorse would race if weight reduction was controlled by feeding and exercise which would by-pass Lasix's negative affects resulting in a combination that would surpass any lasix horse's performance enhancement level? Only problem, it takes much more work by the trainer to accomplish this when a needle a few hours before a race is so much easier! While I am on my soap box here, I have one pet peeve that bothers me to no end on how our modern American racehorses are sent to race on a muddy track! I very seldom see any trainer prepare a horse for the mud by doing up its tail in a "mud tail". As anyone that has been around racehorses very long knows that the natural loose flowing tail is a major catcher of mud that is thrown up from the track and can literally weigh pounds when that horse finally comes off the track! Just common sense can help many trainers win races, if they just think! In short, there are many ways to gain weight reduction other than chemicals!
So what is known about lasix (furosemide) affecting athletic human performances? A study by Caldwell on lasix treated cyclists to assess the effects of dehydration showed that maximum oxygen uptake and workloads decreased. Further, after hydration these same cycling subjects, suffered compromised muscular performance issues. Other studies by Armstrong (1985) on middle distance runners and wrestlers treated with diuretics confirmed the performance reductions issues as well. Studies have shown both single dose and short term diuretic treatments adversely affect maximal workload capacities along with duration levels. In human competitions, it appears any advantages that diuretics may give are quickly counteracted by the many drawbacks. Dehydration lowers aerobic capacity, strength, and metabolic efficiency. Also, it appears that diuretic use affects the glomerular filtration size. Major side effects and toxicity 1) Hypokalemic metabolic alkalosis, 2) Ototoxicity, 3) Hyperuricemia, 4) Hypomagnesemia, 5) Allergic reactions.
A 1993 observational study, Alterations of fluid and electrolyte balance in thoroughbred racehorses following strenuous exercise during training, offers some interesting insights into the training thoroughbred racehorse.
We do know that lasix contributes to major electrolyte imbalances. Lasix not only excretes sodium and chloride; it can affect renal absorption and excretion of other cations (K+, H+, Ca2+ and Mg2+), anions (Cl-, HCO3- and H2PO4-) and uric acid.
Under construction. More to come in the near future.