Reme­dies de­rived from cannabis have been used to treat in­jury in horses since the days of Alexan­der the Great. But what ef­fect does mar­i­juana have on horses? Dr Mac ex­plains.

Farmer's Weekly (South Africa) - - Contents - FW

Hemp and mar­i­juana plants are very closely re­lated (both are clas­si­fied as Cannabis sativa), but they con­tain very dif­fer­ent lev­els of delta-9-tetrahy­dro­cannabi­nol (THC), a psy­chotropic in­gre­di­ent that re­sults in a feel­ing of ela­tion (be­ing ‘high’). Hemp plants usu­ally con­tain less than 1% THC but have higher lev­els of cannabid­iol (CBD), which has been sold on­line as cannabis oil un­der sev­eral dif­fer­ent trade names over the past few years. CBD is re­port­edly a po­tent an­ti­in­flam­ma­tory, which is ef­fec­tive for chronic mus­cle and joint pain. It is also used for pain re­lief in ter­mi­nal cancer pa­tients.

Hemp fi­bre, which has been im­ported by South Africa for many years, is used to make paper and fab­ric. There has been on­go­ing re­search by the Agri­cul­tural Re­search Coun­cil into the pos­si­bil­ity of grow­ing hemp com­mer­cially in the Eastern Cape and KwaZu­luNatal, where mar­i­juana has been known to flour­ish for many years.

The Con­sti­tu­tional Court re­cently le­galised the use of mar­i­juana by adults in their homes. While this has opened the door to changes to leg­is­la­tion re­gard­ing the grow­ing of cannabis, it is well known that mar­i­juana has been used for treat­ing horses in South Africa since 1652. There is also ev­i­dence that cannabis-de­rived med­i­ca­tions were used to treat in­juries in cavalry horses as early as the days of Alexan­der the Great. In Eng­land and the US, cannabis was im­ported from the East and used to treat colic and tran­quilise ner­vous or in­jured work­ing horses. The flow­ers, leaves, stems and roots of the cannabis plant were also in­cor­po­rated into dif­fer­ent tra­di­tional boer­eraat reme­dies for hu­mans and horses dur­ing the 18th and early 19th cen­turies.

It is fairly well known that cannabis was also pre­vi­ously used by South African rid­ers and train­ers to en­hance per­for­mance in jumpers, sad­dlers and race­horses. This was prob­a­bly the case in other coun­tries too, as cannabis and its syn­thetic de­riv­a­tives have been on the In­ter­na­tional Fed­er­a­tion for Eques­trian Sports’ list of banned sub­stances for over 50 years.

Tox­i­c­ity and side ef­fects

Now that there is a pos­si­bil­ity that people could start grow­ing cannabis for home con­sump­tion, it is likely that horses will come into con­tact with th­ese plants. While the cannabis oil in hemp is not very toxic, the high lev­els of psy­chotropic chem­i­cals in mar­i­juana can re­sult in se­vere clin­i­cal signs and even death. Mar­i­juana poi­son­ing in cats and dogs is fairly well recog­nised by small an­i­mal prac­ti­tion­ers in South Africa. Pets oc­ca­sion­ally con­sume home-made mar­i­juana cook­ies or have smoke blown into their faces. At low doses, dogs and cats show di­lated pupils and ex­citable be­hav­iour. How­ever, higher doses can re­sult in coma and even death.

Horses that have grazed cannabis plants also present with di­lated pupils and show ex­citable be­hav­iour. They can be­come dis­ori­en­tated and bolt through fences, or stag­ger and fall. Those that have con­sumed higher doses have mus­cle tremors, sali­vate heav­ily, and their move­ment be­comes un­co­or­di­nated, as though they have been anaes­thetised. They even­tu­ally be­come co­matose and stop breath­ing. Cat­tle and sheep show sim­i­lar signs. Treat­ment is mainly sup­port­ive, fairly ex­pen­sive and un­likely to be suc­cess­ful.

• Dr Mac is an aca­demic, a prac­tis­ing equine vet­eri­nar­ian and a stud owner. Email her at farm­er­[email protected]­ton. Sub­ject line: Horse talk.

DR Mac

ABOVE: The flow­er­ing hemp plant (pic­tured here) is closely re­lated to the mar­i­juana plant. How­ever, it is taller and the leaves are much thin­ner. It is gen­er­ally less toxic to horses and other an­i­mals as it con­tains lower lev­els of the psy­chotropic chem­i­cal THC.

Dr mac

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