Lameness is one of the most common reasons for horse owners to visit the vet. Pain that causes lameness is also important to treat for good horse welfare. There are currently a few medicines authorised for horses that are suitable for use in the home stable. Unfortunately, there are horses that cannot be treated with them because they have too many side effects. For these horses, there are currently no alternatives for pain relief among the authorised medicines, which justifies also studying substances that are not authorised for the animal species in horses.
Cannabidiol (CBD) and cannabidiolic acid (CBDA) are two cannabinoids that occur naturally in the plant Cannabis Sativa. In humans, dogs and rodents, CBD/CBDA provides pain relief, muscle relaxation and has anti-inflammatory properties but no or limited psychogenic effects. Thus, CBD/CBDA may represent a future alternative treatment for pain in horses. However, there is limited knowledge for or against the use of CBD/CBDA in horses and no drugs containing CBD/CBDA are authorised for use in horses. There are, however, oils claiming to contain CBD that are sold over the internet. They have been reported to be used in horses, although there is no reliable information on their effect on horses.
To protect the welfare of horses, the integrity of equestrian sport and to ensure fair competition, both authorised and unauthorised substances that may affect the performance of horses in trotting, racing and equestrian sport are monitored.
While it is essential that horses are healthy and fit to perform, it is inappropriate for them to be given medication that alters their performance in competition or masks symptoms of injury (which may be exacerbated if the horse competes while on medication). The pain-relieving, anti-inflammatory and muscle relaxant properties justify screening for CBD/CBDA in doping control programmes. Unfortunately, plants naturally containing CBD/CBDA have been found to be a contaminant in commercial feed for sport horses and positive test results in doping controls.
As there is no information on the uptake or plasma concentration of CBD/CBDA after oral administration or at what plasma concentration it is pharmacologically active, any findings can be considered as doping violations. Therefore, it is impossible for feed producers to accept CBD/CBDA in their products and the industry must consequently use time and cost consuming control programmes.
More information on the concentrations of CBD/CBDA in the horse that have no effect could reduce this problem.
The knowledge gained from the project will be used to evaluate whether CBD/CBDA can be an alternative treatment for lame horses and provide the equestrian community with data to distinguish feed contamination from therapeutic concentrations of CBD/CBDA in the blood.
The project is carried out in close collaboration with the Swedish Veterinary Agency (SVA) and is funded by the Swedish Equine Research Foundation and the Fédération Equestre Internationale (FEI).
Participating researchers are Carl Ekstrand (SLU), Peter Michanet (SLU), Elin Hernlund (SLU) and Mathilda Salomonsson (SVA).
Carl Ekstrand
Associate Senior Lecturer at the Department of Biomedical Science and Veterinary Public Health; Pharmacology and Toxicology Unit
Telephone: 018-673171
E-mail: carl.ekstrand@slu.se