  MilkShake Myths
Dr. John McCaffrey (Director of Veterinary Services at Racing Victoria Limited), explains the use of bicarbonate of soda in racing (Pacemaker Magazine - March 2005)
Milkshake have become a common, albeit a somewhat unpopular term in racing circles over the last 15 years. A milkshake is a colloquial term used to describe the administration by naso-gastric intubation of 300-600 grams of bicarbonate soda, perhaps mixed with glucose and a variety of other possible additives.
The inevitable question follows: What effect on a horse's race performance do milkshakes have?
The use of milkshake made front page news in New York recently, following the federal investigation of 17 individuals allegedly involved in an illegal gambling ring, accused of fixing at least one race at Aqueduct. The winner of the race, A One Rocket, had been administered a milkshake prior to his 10-length victory. This resulted in a furore as to the purpose of the administration.
In North America, the Racing Medication and Testing Consortium are in process of recommending uniform penalties and testing protocols for milkshaking by regulatory bodies in the various racing jurisdictions. Meanwhile, Australia has refined its testing protocols to an extremely high standard.
The practice of supplementing a horse's feed with various electrolyte mixtures - in many cases as simple as a teaspoon of baking soda (or Bicarbonate Soda NaHCO3) has been considered an acceptable routine feeding management practice for many years. When a horse is exercising it uses two forms of energy production: aerobic and anaerobic metabolism. Anaerobic metabolism results in the muscle cells environment becoming increasingly acidic. As the horse exercises, there is an increase in lactate in the muscle cells (and eventually in the bloodstream), therefore limiting the muscle activity and leading to fatigue. Therefore, as the lactic acid builds up, the horse slows down.
The concept with milkshaking is that if you can increase the alkalinity of the blood (pH of the blood), this would buffer the build-up of lactate. In human terms (albeit simplistically), this equate to the tightening of muscles athletes experience towards the end of strenuous exercise. By increasing the pH of the blood, you can remove or delay that effect, therefore not run faster, but rather maintain your maximum speed for longer.
A number of experiments have been performed over the years both in human and equine exercise physiology in an attempt to demostrate what effect varying quantities of bi-carb might have on high performance. Evidence produced by the studies has been somewhat equivocal; some studies show improvement in human and horse exercise capacities (increased run to fatigue times), while some studies haven't. In some instances, the experimental design has been flawed, bringing the results and conclusions into question.
The conclusion that can be drawn is that the administration of significant quantities of bi-carb can affect performance in certain circumstances. However, in what way does it affect performance?
It appears that in thoroughbred racing for races of 90 seconds or longer (or races longer than a mile), horses that have received 300-600 grams of bi-carb would, in all likelihood, receive an advantage. It would appear that in sprint races there is no particular advantage, as horses produce little lactic acid during races of six furlongs or less. It is interesting that in both humans and horses on occasions, the administration of large amounts of bi-carb can cause gastric disturbances and therefore, have a negative effect on performances.
Anecdotally, there seems to be little question within the standarbred industry, at least, that in races of two minutes or longer, the administration of bi-carbdoes assist performance. For this reason, in the late eighties Professor Cliff Irvine, from Christchurch, New Zealand, developed a system to detect the illicit use of bi-carb in order to control the problem (real or perceived)
Australia soon came on board. The detection system Australian authorities have put in place is different to these of Professor Irvine's - Australia uses a blood gas analyser called the Beckman Elise. The purpose of this is to control the administration of bi-carb. A program of systematic pre-race testing has achieved this. This preventative approach to control bi-carb usage over 15 years of testing in Victoria has resulted in only 14 positives from 13 trainers.
Pre-race testing involves analysis of blood samples on track in a mobile laboratory. In Australia, the methodology is aimed at providing an estimation of the horse's plasma total carbonate dioxide level (plTCO2 concentration). plTCO2 concentration parallels plasma HCO3 concentration.
Testing protocols have been refined considerably over the years. When a horse is pre-race blood tested, it is under very rigid protocols, providing consistent results through the application of reliable and reproducible methodology.
It is interesting to note that in some states in North America, they control this problem by using slightly different approaches using concepts such as significant iron difference.
Numerous studies have been conducted to determine the normal range of plTCO2 concentrations in horses, as it is an endogenous substance. For testing purposes, these studies were designed to determine a threshold level beyond which a concentration of plTCO2 could not be obtained naturally and which would indicate, therefore, that there had been an illicit administration of bi-carb by stomach tube or by feeding.
Concurrent administration of glucose wil improve the absorption of bi-carb and give a greater elevation in plTCO2 concentration. Similarly, if you withhold water from a horse and administer bi-carb, it will further increase the plTCO2 levels.
Screening for the illict use of bicarbonate resulted for two reasons: 1. There was a perception (at the very least) that people were receiving an unfair advantage through this practice and 2. The practice may also be undertaken to try and mask the administration of other prohibited substances.
By administering large amounts of bi-carb, one of the consequent effects was an increased diuresis (increased flow of urine). The concern here is that diluting urine may make the detection of prohibited substances more difficult.
In some limited studies, conducted in Australia, is, in fact, does not appear to be the case. However, by virtue of this somewhat limited scope of these studies, one could not definitively rule out the possibility of other prohibited substances being administered, especially drugs that had an acid pH.
The administration of alkaline substances (such as bi-carb) can effect the rate of excretion of some drugs. They can be excreted in lower concentrations for a longer duration or, alternatively, be excreted more rapidly at higher concentrations. Drug excretion is, however, an extremely complex issue affected by many factors.
When bi-carb is administered via nasogastric intubation (stomach tube), the peak plTCO2 level would be generally reached somewhere between 4-6 hours after administration. Under the Australian Rules of Racing, it is illegal to stomach-tube a horse within 24 hours of racing.
Sodium bicarbonate is not the only substance that will elevate plTCO2 levels. Other alkalinising agents include sodium citrate, sodium lactate, sodium succinate, tris buffer and sodium acetate. These substances are referred to as alkalinising agents and trainers are advised not to administer them within 24 hours of racing to comply with the threshold rule. All can elevate plTCO2 levels and, in fact, some of them on a weight equivalent basis are more effective and do so for longer than bi-carb itself.
A large-scale, controlled study was conducted using 550 racehorses throughout Australia and the result of that study showed that 36.0 milliMols (mMols) was the level that coud not be exceeded by natural means. This is now the level that is enshrined in the Rules of Racing both in Australia and Internationally (by the IFHA).
The actual resting level of plTCO2 in a normal racehorse that has not received any electrolyte supplementation was shown in one, large-scale study to be 30.8 mMols (plus or minus 1.4 mMols). Some horses were 34.0 mMols, some horses 28.0 mMols (scientifically, to calculate a threshold, the accepted convention is that at least three standard deviations from the mean must be calculated). This gives a level of 35.2 mMols.
In statistical terms, the odds of a normal horse having a plTCO2 concentration in excess of 35. mMols is one in 9,900. To exceed 36.0 mMols it would be one in 13,000, to exceed 36.2 mMols would be one in 24,000 and most importantly, to exceed 37.2 mMols is one in 641,000 (according to the 2003-2004 Australian Racing Fact Book, the total number of horse racing in Australia are 31,126, while the number of starters are 200,188). Therefore, statistically, a horse that exceeds 37.2 mMols without supplementation would be an extremely unlikely event.
In Victoria, we pre-race blood test approximately 8,500 horses per year. You can't test plTCO2 using urine, only blood.
36.0 mMols plus or minus 1.2 mMols (the critical limit being 37.2 mMols) indicates a high degree of certainty that if a sample exceeds that level, there is a problem.
In order to confirm the initial test results, Australia has a system whereby a reserve sample must be independently tested in another (approved) laboratory in Australia, New Zealand or Hong Kong. plTCO2 testing has to be conducted reasonably promptly as blood samples can't be indefinitely stored, so testing needs to be completed within three or four days. After this time the plTCO2 level decreases.
Based on significant anecdotal and some scientific evidence, it is reasonable to form the view that under certain exercise conditions, milkshaking has the potential to influence a horse's performance.
While it will not improve a hore beyond its natural athletic potential, it can enable the horse to perform to that potential for longer than would be otherwise possible. This is the primary reason for many racing jurisdictions throughout the world moving to control the practice.
Semantics or not, from an Australian perspective, the practice of milkshaking has represented a significant threat in the integrity of the racing industry. The regulatory mechanisms now in place have effectively removed that threat.
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