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Prohibited Substances, Feed, and the Performance HorseBy Dr. Peter Huntington · June 22, 2011

Drugs in sport are a hot issue, and the publicity received by human athletes who test positive during international competition is immense. Drug abuse is equally topical among equine athletes. Positive swabs have caused a number of horses and riders to be disqualified and lose individual or team medals in recent years. In racing, races are lost and the value of the horse is diminished when positives occur. 

Performance horses are subjected to a mind-numbing array of regulations, depending on the organization that oversees the competitions. It is virtually impossible to detail all of the individual rules and regulations regarding the use of drugs and medications for each horse organization at every event. To compound the problem, the list of banned substances and sensitivity of detection changes on a daily basis.

The sensitivity of testing has increased dramatically since testing procedures were initiated. For example, the sedative acepromazine, which in 1960 could not be detected in the urine of horses, can now be detected for up to 5 days after administration. It must also be remembered that in many cases, the authorities are testing levels as low as several parts per billion (ppb). To put this into context, if you are 32 years old, you have lived about one billion seconds. Close your eyes for one second — that is one ppb! The use of such technology is a strong deterrent against the deliberate use of performance-enhancing drugs in horses.

Can honest horseman be caught with a positive drug test? In some cases the answer is yes. It is possible to inadvertently administer a forbidden substance via environmental contaminants of feed, supplements, or natural products. A therapeutic drug may also have an unusually prolonged excretion time in a particular horse. It is a common misconception that natural products do not contain any drugs and therefore do not contravene the rules of racing or FEI (Federation Equestre Internationale); this is not so. For example, opium, morphine, and heroin are natural products derived from just one plant. Many common drugs are derived from plants, and it can be very difficult to ascertain from the label if there is a prohibited substance within the product.

The use of herbs in equine diets has become popular in recent times, but the use of certain herbs has been classified as “doping” under a number of horse sport regulatory authorities. For example, rosemary and caffeine are considered stimulants and are banned under FEI rules. The FEI website has a complete list of prohibited substances in equestrian sport.

The FEI has always cautioned athletes, trainers, grooms, and veterinarians against the use of herbal medications, tonics, oral pastes, and products of any kind, the ingredients and quantitative analysis of which are not known in detail. Many of these products could actually contain one or more prohibited substances. Riders administering an herbal or so-called natural product to a horse for health reasons or to affect its performance, having been informed that the plant origin of its ingredients do not violate the FEI regulations, may have been misinformed.

The use of any herbal or natural product to affect the performance of a horse or pony in a calming (tranquilising) or an energising (stimulant) manner is expressly forbidden by FEI regulations. The use of a calming product during competition may also have important safety consequences. The FEI does not test or approve herbal or natural products to verify a possible violation of the FEI rules and regulations. Therefore, a claim that the product does not violate the FEI rules or is undetectable by drug testing is the sole responsibility of the manufacturer or individual making such a claim. The use of an herbal or natural product may result in a positive test result, contrary to the claim by the manufacturer or marketing agent.

Regulatory authorities have rightly recognized that many substances, or their metabolites, that produce a “positive” are present at trace levels and are likely derived from legitimate therapeutic medications or are of a dietary, environmental, or endogenous (from within the horse) origin. Previously a positive of any magnitude was deemed an offense, but today there are approved thresholds for certain medications within the racing and FEI regulations.

Within the FEI list and within the new FEI Equine Anti-Doping and Controlled Medication Regulations (EADCMR), there are two main categories of regulated substances:

  • Banned substances. These are substances that have been deemed by the FEI to have no legitimate use in equine medicine and/or have a high potential for abuse (e.g., human antidepressants, antipsychotics, nervous system stimulants, etc.).  These simply should not be found in any horse at any level at any time.
  • Controlled Medication substances.  An exhaustive list of medication that is prohibited in competition, and made up of all known substances that are recognised as therapeutic and/or commonly used, but have the potential to enhance performance at certain levels. Some examples might be anti-inflammatories (see note below about allowed levels), local anaesthetics, bronchodilators, cough suppressants, and other commonly and uncommonly used medications. Clearly substances on this list may also enhance performance depending on the timing and size of dose.

No matter what the circumstance, competition horses are expected to compete with no banned substances or controlled medication substances in their systems unless at a level defined and approved by FEI regulations.

Some of the more common feed contaminants are described below:

1. Hordenine. Hordenine is a naturally occurring plant alkaloid produced during the sprouting phase of barley, closely related to epinephrine, known commonly as “elephant juice.” Brewers grains, malt combings, distillers dried soluble, and sprouted barley may contain hordenine.  There is no threshold allowance for hordenine and therefore it is advisable to avoid the inclusion of any of the above mentioned products in the diet of a performance horse. However, the FEI has recently increased the screening threshold for hordenine.

2. Dimethyl sulfoxide (DMSO). DMSO is found in the urine of all horses and is believed to be almost entirely of dietary origin, most likely from lucerne (alfalfa) hay. As a drug, DMSO is used as a topical anti-inflammatory and analgesic agent.  A threshold of 15.0 mg/l of urine or 1.0 mg/l of plasma is permitted.

3. Salicylate. Salicylic acid (salicylate) is a normal metabolite in horses urine and occurs naturally in several plants, notably lucerne (alfalfa) and in  the bark of some trees such as willows. The drug is used as an anti-inflammatory agent (aspirin), in topical creams and powders to treat ringworm and skin problems, and as an active ingredient in linaments and medicated washes. Authorities allow for natural sources of salicylic acid with a maximum tolerance level of 750 mg/l of urine or 6.5 mg/ l of plasma.

4. Morphine. Opiates such as morphine can cause central nervous system stimulation in horses. Morphine occurs naturally in a number of pasture species and in poppy seed, which is used in certain bakery products. Codeine and heroin is metabolised to morphine and are other potential sources of contamination in horses. Poppies grow wild in many countries and their prevalence depends on seasonal and geographic considerations, so you should carefully check your oats for presence of poppy seeds and seek veterinary advice if you see them. There is no threshold for morphine.

5. Arsenic. Arsenic occurs throughout nature and is found in all horse urine; however, it has been popular as a stimulant in small amounts and to slow horses down in larger amounts. The international threshold for arsenic is 0.3 mg/l in urine.

6. Caffeine. Caffeine is a methylxanthine alkaloid and is widely distributed in nature. The xanthine alkaloids also include theophylline (from tea) and theobromine (from chocolate). In addition to these sources, many of the so-called “natural” products on the market also contain xanthine alkaloids. Guarana is actually 60% caffeine and is commonly sold as an energy-uplifting product. Administration of products containing guarana extract would likely result in a positive swab. Methylxanthine compounds are mild stimulants, bronchodilators, and vasodilators.

Because of the widespread distribution of caffeine, the FEI has removed caffeine from its list of prohibited substances and some regulatory authorities allow a low threshold in plasma and urine samples. However, other jurisdictions have a zero tolerance to caffeine in swab samples. An oral dose of caffeine can be detected for up to ten days.

7. Theobromine. Cocoa bean meal is a source of the alkaloid theobromine as are the products of cocoa bean such as chocolate. It has been shown that the feeding of 10 M&M's® with peanuts would produce a detectable concentration of theobromine and caffeine in the horse's urine for 48 hours.  Shipping of products in containers commonly used to transport cocoa bean meal or cocoa husks is another potential source of contamination. Given the high risk of inadvertent administration of theobromine to horses, a threshold of 2.0 mg/l of urine is used by the major regulatory authorities.

8. Bicarbonate. Sodium bicarbonate has long been popular as a buffer that, when added to feed in an unprotected form or administered via stomach tube (milkshaking), may delay the onset of fatigue brought about by lactic acid accumulation. A maximum threshold for sodium bicarbonate in plasma has been set by several regulatory authorities. Protected sodium bicarbonate, designed to be released into the horse's large intestine and used for combating hindgut acidosis, has been fed to horses successfully without exceeding allowable tCO2 threshold. It should be remembered that horses vary in their reaction and excretion rates for additives/drugs, so it is not possible to set a definitive safe dose that is applicable to all horses. Bicarbonate is a common additive in ruminant diets and further illustrates the dangers of using feeds other than those specifically designed for horses. Other alkalising agents such as citrate can also produce an effect that may exceed the allowable threshold.

9. Feed bin or environmental contamination. Several positive swabs have resulted from contamination of the feed bin or stable environment with banned substances such as isoxsuprine. In some cases, treatment of the previous stall occupant has led to a positive swab in a subsequent occupant, weeks after the first horse was treated. Another avenue for a positive swab is contamination of the horse's feed by residue from a handler's illegal drug use. Residue of cocaine use on the hands of someone who mixes the feed may lead to a positive swab.

10. Ractopamine.  Ractopamine is a muscle-building agent used in pig feed and supplements, and it has been found in a number of positive swabs in performance and racehorses in recent years. Some of these have related to inadvertent contamination of horse feed by ractopamine, where the horse feed has been made in a mill that also makes pig feed containing the drug. In other cases, there has been no direct link with contaminated feed.

Certain substances are exempted by some authorities including oral glucosamine and chondroitin, oral antiulcer medications, and oral vitamins and electrolytes. However, under some rules of racing, vitamins administered by injection are classified as a prohibited substance, and no injectible may be administered whilst under FEI rules without an Equine Therapeutic Use Exemption.  This must be completed by a treating veterinarian and countersigned by the FEI Veterinary Delegate present at the event prior to injection or treatment.

The list above is by no means exhaustive and simply serves to highlight some of the more common sources of inadvertent contamination of performance horse diets with substances that may produce a positive drug test. 

Some measures that the concerned rider or trainer can take in order to avoid or minimise the risk of contamination include:

1. Buy commercial horse feeds only from reputable manufacturers who operate under the most stringent quality-control standards. The feed should be accompanied by documentation that lists the composition and comprehensive details of the nutrient content. A bag tag that states only protein, fat, and fibre percentage would not instill confidence. Full disclosure shows that the technical and production teams at the mills are operating under best practice and are aware of the problems of prohibited substances and take these into account, both in their manufacturing and in their transport and storage of raw materials and finished products.

2. When possible purchase concentrates and hay from reputable merchants with an understanding of the quality issues relating to performance horses. It is unwise to purchase hay or concentrates from farmers who may have stored these products next to feed or supplements intended for other animal species. Check oats for poppy seed contamination. Use only recognized foodstuffs from reputable sources to reduce the risk of contamination.

3. At elite FEI-level events where drug testing is being conducted, keep small samples of feed (250 grams) and supplements (30 grams) along with bag tags and/or a record of the batch number, from about one month prior to the commencement of a competition period. These samples should be stored in cool, dry environment away from sunlight for six months. If a positive test is discovered, you will have a reference sample in the event of any problems. Ensure that samples are taken near the bottom of the bag where fine material may accumulate.

4. Do not allow chocolate or coffee to contaminate a feed room or be fed to a horse.

5. Do not store feed from other species in any area used for preparing or storing horse feed.

6. Do not put anything in a horse's mouth unless the contents and composition of that feed/supplement is known. This is particularly true for herbal or so-called “natural” products and many substances that make grandiose claims for efficacy. They should be completely labelled with the ingredients and analysis before you use them.

7. Many substances can be absorbed through the skin and detected in tests. Be careful of liniments that may contain oil of wintergreen, which contains methyl salicylate.

8. Seek veterinary advice regarding the cessation of any treatment prior to competition.

It is the responsibility of riders, trainers, and veterinarians to be aware of the regulations relating to their particular area of equine sport. More importantly, it is the responsibility of the riders and trainers to ensure that they do not feed, inject, or apply anything to their horses that may contravene these rules. Ignorance is not a legitimate plea against a positive drug test.

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