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different binders have varying affinity for the variety of mycotoxins that exist. Much more work is needed in this area.


Prohibited substances


There is a risk of prohibited substance contamination from forage, feed and supplements with respect to the rules of racing (e.g. BHA UK, http://rules.britishhorseracing.com/Home) or competition (http://inside.fei.org/fei/cleansport/horses/). In some instances, this may relate to a prohibited substance being an identified component of the product, for example, capsaicin from red peppers, or valerenic acid from valerian. It is important that veterinarians maintain their knowledge and understanding of the global rules of racing and competition (FEI or other body), especially with regards to any published lists of doping or medication substances in order to best advise their clients. In addition to this, there is also a risk from inadvertent


contamination with naturally occurring prohibited substances, for which there are historical cases of contamination (see FEI vs. Paget and McNab). These substances are often analysed within a prohibited substance screen, which may form part of a quality system e.g. BETA NOPS (http://www.beta-uk.org/pages/feed-safety/beta-nops- scheme.php) designed to reduce the risk of inadvertent contamination of feed and or supplements. Typical components of a standard prohibited substance screen may include caffeine, theobromine, theophylline, hyoscine, hordenine, atropine and morphine, which have all been shown periodically to contaminate commonly used horse feed ingredients. However, there is also an additional identifiable risk of inadvertent contamination with other plant, herbal or spice based ingredients that contain naturally occurring substances deemed as prohibited by the regulators (Table 4). The risk of this latter contamination increases as more ingredients are sourced from countries where recognised quality control procedures are less well established. Whilst it is not possible to eradicate the risk of contaminating prohibited substances, veterinarians can advise their clients to take a number of steps to reduce their risk of using a contaminated product by:


• Being fully aware of all ingredients within a product and whether they comply with the relevant rules.


• Being fully aware of the quality control procedures employed by the manufacturing company to reduce risk


TABLE 4: Nonexhaustive list of potential contaminants from plant or herbal ingredients that have resulted in a post-race or competition positive result


Prohibited substance Capsaicin


Valerenic acid


Ephedrine Cathinone Digitoxin


Synephrine Yohimbine Vincamine Reserpine


Plant species Capsicum sp.


Valerian Valeriana cetica Ephedra sp. Khat


Foxglove


Bitter orange Rauvolfia sp.


Lesser periwinkle Rauvolfia sp.


from prohibited substances (see also http://www.beta- uk.org/pages/feed-safety/beta-nops-scheme.php).


• Encouraging riders, owners or trainers to maintain a feed and supplements log book to establish feeds used, batch numbers etc. and to also retain samples of each batch of product where practical for a relevant period of time e.g. 3 months.


Conclusion


Equine nutrition is a specialist subject area and it is unrealistic for all veterinarians to have comprehensive expertise in this field. However, there are a few key areas where nutritional


knowledge is advantageous to clinical assessment as well as the health and welfare of the horses and ponies in their care. There is supporting nutritional advice available to veterinarians from veterinary nutritionists and other paraprofessionals, either inside or outside the commercial feed sector. However, it is worth noting that with the exception of the veterinary ECVCN diplomate qualification, the term equine nutritionist is not a protected title in Europe and so some background knowledge as to the qualifications and experience of any specialist advisor is warranted as discussed in Harris (2016).


Authors’ declaration of interests


P. Harris works for WALTHAM/MARS Horsecare and C. Dunnett works for Independent Equine Nutrition and Racing Blue.


Ethical animal research Ethical review not applicable for this review article.


Source of funding Other than support from the authors' place of work there was no private or commercial funding for this work.


Authorship Both authors contributed equally.


References


Abdel-Wahhab, M.A. and Kholif, A.M. (2008) Mycotoxins in Animal Feeds and Prevention Strategies: a review. Asian J Ani Sci., 2,7–25.


Al Jassim, R.A., Scott, P.T., Trebbin, A.L., Trott, D. and Pollitt, C.C. (2005) The genetic diversity of lactic acid producing bacteria in the equine gastrointestinal tract. FEMS Microbiol. Lett. 248, 75-81.


Anon (2007) Nutrient Requirements of Horses, 6th Revision. National Research Council, National Academy Press, Washington, DC.


Anon (2009) Safety of Dietary Supplements for Horses, Dogs, and Cats. Animal Nutrition Series, National Research Council of the National Academies Press , Washington, DC.


Argenzio, R.A., Southworth, M. and Stevens, C.E. (1974) Sites of organic acid production and absorption in the equine gastrointestinal tract. Am. J. Physiol. 226, 1043-1050.


Argo, C.M, Dugdale, A.H.A. and McGowan, C.M. (2015) Considerations for the use of restricted, soaked grass hay diets to promote weight loss in the management of equine metabolic syndrome and obesity. Vet. J. 206, 170-177.


Bonin, S.J., Clayton, H.M., Lanovaz, J.L. and Johnston, T. (2007) Comparison of mandibular motion in horses chewing hay and pellets. Equine Vet. J. 39, 258-262.


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