Medicinal herbs can be beneficial to the health of sporting horses, but competition rules and regulations may prohibit their use in some cases.
Sporting horses used in 800 BC were fed supplements to increase endurance and through the centuries, war horses and medieval steeds were given “remedies” to boost strength and stamina (Higgins 2009). Rules prohibiting the use of “exciting substances” appeared in England by 1666 (Higgins 2009).
Physical effects of training
Many modern sporting horses never completely adjust to the pressures of competition and remain in a state of chronic stress (CS) throughout the show season. The subtle signs are often overlooked or misinterpreted as behavioral issues (King 2006).
The resulting cortisol increase causes:
1. Lowered athletic performance.
2. Gastric ulcers.
(a) 58% of horses that had been transported to at least one event in the 30 days prior to endoscopy (McClure, Glickman and Glickman 1999).
(b) 93% of endurance horses had squamous gastric ulcers (Tamzali et al 2011).
3. Increased susceptibility to infections and slow recovery from illness and injury (King 2006).
Research in herbs
Evidence is accumulating for the benefits that can be gained by inclusion of medicinal herbs in managing equine health. Ergogenic effects of equine herbal products include boosting the immune system, improving antioxidant status, increasing coping abilities and concentration (Bergero 2006). Herbs showed benefit in several equine disorders, including recurrent obstructive pulmonary disease, allergic dermatitis and joint inflammation, in addition to modulating immune responses in healthy horses (Pearson 2008).
Herbal properties with relevance for performance horses
Herbal supplements that affect the immune system can be classified as adaptogens (increase resistance to stressors), immunostimulants (activate the nonspecific, or innate, defense mechanisms), or both.
A common problem for performance horses is “sport horse anemia”. This reduces oxygen delivery to the muscle cells during effort, thus decreasing the anaerobic threshold with the ultimate result being loss of performance. Ginkgo (Ginkgo biloba) is used in this case with good result (Bergero 2006).
A number of herbs demonstrate anti-inflammatory and pain relieving activity.
1. Ginseng (Panax ginseng) exerts an inhibitory effect on pro-inflammatory cytokines and COX-2 expression (Williams and Lamprecht 2007). The main components include glycosidal saponins.
2. Equine studies have also tested the anti-inflammatory effects of a single dose of ginger (Zingiber officinale) suggesting that post-exercise cardiovascular recovery time is reduced (Nettie 2004). Since ginger is also an antiulcerongenic, many ulcer-relief herbal supplements for horses contain ginger as a major ingredient.
3. Yucca (Yucca schidigera) contains steroid-like saponins that produce anti-infl ammatory, antioxidant and anti-spasmodic effects to reduce pain associated with arthritis (Cheeke et al 2006).
4. Devil’s claw (Harpagophytum procumbens) is often called “herbal bute” (James Hart) and is primarily sold for its pain reducing properties (Williams and Lamprecht 2007). One equine study in horses with naturally occurring osteoarthritis looked at the effect(s) of a proprietary polyherbal composite joint supplement containing devil’s claw. An anti-inflammatory effect was observed in the horses due to a reduction in prostaglandin e2 synovial fluid content (Pearson 2008).
5. White willow, meadowsweet and capsaicin also have anti-inflammatory and/or analgesic properties (King 2006).
Adaptogenic studies on exercise capacity in many species have produced conflicting results. Some studies showed a positive effect on exercise capacity, while others showed no effect King (2006). An effect is most likely in unfit subjects and is most consistently seen as an increase in endurance. Most studies in “fit” human athletes show no effect on performance. So far, practical use in sporting horses supports a similar conclusion: that adaptogenic herbs should not be considered performance enhancing substances, but rather substances which simply support optimal health and function.
Drawbacks in the use of herbs in horses
Most herbs have not been clinically tested, especially in the horse. Adulteration is a common cause for toxic or adverse reaction to herbs. Adulteration includes substitution of herbs and intentional or unintentional contamination with active components, drugs, pollutants or pathogens (Fors 2009 cited in Mills and Bone 2005).
Concerns with herbs in competition
Herbal products contain ingredients able to affect body systems and thus can, by definition, be prohibited substances in competitions. An excerpt from one research study illustrates how drugs and herbs in equine competition are sometimes perceived as one and the same: “The future of equine drug metabolism in the area of doping research will be influenced by several factors including the increasing threat of ‘designer’ and herbal-based products” (Scarth, Teale and Kuurane 2010).
At the 2008 Beijing Olympics several riders were disqualified from competition for testing positive for capsaicin (Capsicum frutescens). Capsaicin is banned by the Federation Equestre Internationale (FEI) as it stimulates P substance and has pain-relieving properties. The theory is that after the initial burning sensation, which is associated with heightened sensitivity, follows a period of reduced sensitivity. If rubbed onto a horse’s shins just before competing, a rider can time the period of heightened sensitivity associated with the burning to encourage the horse to pick up his legs over the jumps to avoid hurting himself, thereby potentially improving performance (Birch 2011). However, capsaicin does not appear on the FEI Medication Class A list of banned substances with other herbs such as valerian, so confusion does exist. Part of this may be that only recently has a test been developed to detect it (Farrington). One competitor’s positive came from capsaicin in an anti-chewing product he had put on his horse’s bandages and stall (Hart nd).
Rules of equestrian sport affecting herbal usage
FEI (the world governing body for equestrian sports) distinguishes between medication (i.e. veterinary treatment provided to safeguard the animal’s health and welfare) and doping (i.e. the deliberate intent to affect the performance of a horse or to mask an underlying health problem). There are presently three classes of offence: Doping, Medication Class A and Medication Class B. Medication Class A (therapeutic agents that could influence performance, e.g. relieving pain, sedating, stimulating or producing/modifying physiological or behavioral effects) is the category for most herbs (Higgins 2009).
United States Equestrian Federation (USEF 2010) rules are subject to the Therapeutic Substance Provisions. It states in part: “Trainers, owners, exhibitors are cautioned against the use of medicinal preparations, tonics, pastes, powders, and products of any kind, including those used topically, the ingredients and quantitative analysis of which are not specifically known, as they might contain a forbidden substance. This is especially true of those containing plant ingredients. The plant origin of any ingredient does not preclude its containing a pharmacologically potent and readily detectable forbidden substance.”
A further caution (USEF 2010) states: “Persons administering a so-called herbal or natural product to a horse or pony to affect its performance, having been comforted by claims that the plant origin of its ingredients cause it to be permitted by the rules as well as undetectable by drug tests, might have been misled. Trainers should be most skeptical about any claims by manufacturers or others that their preparation is ‘legal’ or permissible for use at competitions. It is the longstanding policy of USEF that it does not approve, endorse or sanction herbal, natural or medicinal products of any kind.”
Forbidden herbal substances listed in the USEF’s Drugs and Medications Guidelines handbook include: belladonna, camphor, capsaicin, chamomile, comfrey, devil’s claw, hops, kava kava, lavender, lemon balm, leopard’s bane, night shade, passion flower, rauwolfia, red poppy, skullcap, valerian and vervain.
The United Kingdom (UK) Rules of Racing (2010) state that medications, including herbal products, may be used during training but that they must be withdrawn so that their ingredients are not present on race days, and must not be administered on race days.
Detection
The objective of analytical screening is to detect any trace of drug exposure (parent drug or metabolites) using the most powerful analytical methods, generally chromatographic/ mass spectrometric techniques (Toutain 2010). Problems are now arising because the high level of sensitivity in current screening methods allows the detection of totally irrelevant plasma or urine concentrations of legitimate drugs for long periods after their administration.
Therefore new approaches for legitimate compounds based upon pharmacokinetic/pharmacodynamic (PK/ PD) principles are being developed (Scarth, Teale and Kuuranne 2010).
The detection time (DT) is the approximate period of time for which a drug (or its metabolite) remains in a horse’s system such that it can be detected by laboratory analysis. The withdrawal time (WT) for a drug must be decided upon by the treating veterinarian and is likely to be based on the DT plus a safety margin, chosen with professional judgment and discretion to allow for individual differences between horses such as size, metabolism, degree of fitness, etc.
FEI (2010) states that veterinarians have to advise owners or trainers on appropriate WTs to guarantee that their horses may safely compete after drug administration. DTs typically range between three and ten days. There is no mention of WTs for herbs or herbal extracts.
A pilot study in the UK of tail-hair analysis suggests that this method could be used as a diagnostic tool in the investigation of drug abuse. Hair analysis is complementary to urine/blood testing and is noninvasive, impersonal and can facilitate retesting. The data presented suggest that hair analysis may become a usable technique for the retrospective detection of drug administration in horses (Dunnett and Lees 2004).
Inconsistencies in banned substances
There are many discrepancies between the lists of the various equestrian organizations. The USEF banned substance list contains herbs by their common names and is more extensive than either those of FEI or the Jockey Club UK.
In contrast, FEI does not list the herb by name, rather it identifies prohibited substances according to their active constituents and the physiological systems upon which they act. Lobeline, an alkaloid of the Lobelia plant found in Indian tobacco (Lobelia inflata), cardinal flower (Lobelia cardinalis) and star of Bethlehem (Hippobroma longiflora), is listed as a respiratory stimulant. Valerenic acid, a sesquiterpenoid constituent of the valerian plant is listed as a tranquilizer. FEI states that it reserves the right to alter the list at any time without prior notice, and USEF makes clear that its current list of banned substances is only partial, perhaps in a concerted effort to stay ahead of potential abusers.
Equistro (2009) reported that one of the authorized FEI analytical laboratories announced that it had the possibility to test for “harpagosides”, the presumed active ingredient found in devil’s claw. This may be true, but the process whereby an herb officially becomes an illegal substance is vague and as a result keeps all competitors guessing. It has been suggested that devil’s claw and chamomile are likely to be the next herbs added to FEI’s prohibited list.
Consistent regulations regarding herbs may be far off, since the governing bodies for equestrian sports have not come to an agreement on even which drugs should be permitted in competition. Phenylbutazone, along with Regumate, Gastroguard and antibiotics are now allowed in FEI competitions, yet continue to be banned by the German Equestrian Federation. These medications are now included on the FEI Progressive List as they are no longer considered performance enhancing. Following this logic, it stands to reason that adaptogenic herbs, having been found not to be performance enhancing substances in fit subjects, should also be permitted.
Herb/drug interaction
The most common medications used in on-track sporting horses are furosemide, anti-inflammatories and bronchodilators. Interactions have been reported. A number of herbs have been associated with adverse reactions with bronchodilators including St John’s wort (Hypericum perforatum), ginkgo (Ginkgo biloba) and cardospermum (Cardospermum halicacabum). (Pearson 2008).
Studies in many species have indicated drug interactions with Echinacea (Robinson 2006); ginseng (species); any herbs containing salicin such as white willow (Salix alba) or meadowsweet (Filipendula ulmaria); ginkgo, garlic, ginger, bilberry, dong quai, feverfew, turmeric, chamomile, motherwort, horse chestnut, fenugreek and red clover (Abebe 2002).
Summary
Herbs have been used for centuries to enhance the performance of many sporting horses. Herbal medicine will continue to be used alone or as an adjunct to drug therapy for the sport horse. Under the current rules of the numerous official national and international equestrian committees, the use of herbs and herbal extracts in competition remains an under-researched and controversial topic. Greater understanding and knowledge of herbal medicine within the equine industry will hopefully dispel some concerns and lead to more appropriate use to help improve equine health and wellbeing.
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