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Herbs for horses: what the evidence shows and when caution is needed
How to assess herbs for horses: what is permitted as feed, how thin the evidence is for devil's claw, milk thistle, chasteberry, rose hip and nettle, and why herbs are tricky in competitive sport.
The short answer
Herbs for horses are feed, not medicines, and must not promise any healing effect 1. For most herbs, there are no controlled studies in horses. In German competitive sport, phytotherapeutics are banned in general, and devil's claw is named explicitly 2. So choose herbs deliberately, include them in the ration calculation and check every ingredient in the ADMR database before competitions 3.
Feed, not medicine
Herbs that you feed to your horse are legally feed. Feed has its own rules on labelling and advertising claims; it must not be advertised as preventing, treating or curing disease 1.
For you, this means: a herbal product is not a treatment. With lameness, coughing, liver or hormonal problems, the cause should be investigated by your vet.
What is known about common herbs
For most herbs, there are no controlled studies in horses on health problems. The existing studies often only measure whether and for how long a compound appears in the blood.
- Devil's claw: a study with six horses found harpagoside in plasma for up to nine hours; effectiveness was not investigated 4.
- Milk thistle: only 0.6 per cent of silibinin from the feed was absorbed 5.
- Chasteberry: the BEVA guideline sees no effect on ACTH and no benefit in addition to pergolide 6.
- Rose hip: horses produce vitamin C themselves in the liver 7.
- Nettle: the leaves contain a lot of calcium, potassium and silicic acid 8.
| Herb | Evidence in horses |
|---|---|
| Devil's claw | blood levels only, banned in competition |
| Milk thistle | barely absorbed, no study in horses with liver disease |
| Chasteberry | no effect on ACTH according to guideline |
| Rose hip | vitamin C, which horses produce themselves |
| Nettle | rich in minerals, no horse study |
Brief overview of the evidence in horses; details in the individual articles.
Herbs in competitive sport
The FN's anti-doping and medication control rules (ADMR) explicitly list devil's claw as prohibited medication and also ban phytotherapeutics in competition in general 2. The FEI list also covers substances that are not named but have a similar structure or effect 9.
According to an FN vet, a limit of 0.5 per cent per herb applies to many herbs in feed 10. This is a statement from an interview; the ADMR database is binding 3.
Natural does not mean harmless
A natural origin does not protect against undesirable plant compounds. Since June 2026, the European Commission has recommended monitoring pyrrolizidine alkaloids in feed, explicitly including herbs, herbal extracts and compound feeds containing herbs 11. These compounds are found in ragwort, among other plants.
With herbal mixes, ask about origin and quality control. A promise such as “guaranteed free from toxins” is not possible, but documented testing is.
Key takeaways
- Feed must not be advertised as treating or preventing disease 1.
- For the common herbs, there are mostly only blood level or tolerance data in horses 45.
- In competitive sport, the person presenting the horse is liable, even for contaminated supplements 2.
- Herbs and herbal mixes are among the feeds that the EU wants monitored for pyrrolizidine alkaloids 11.
Frequently asked questions
Which herbs are good for horses?
None of the common feed herbs has a proven healing effect. The nutrients they supply can be included in the calculation like any other feed, for example the minerals in nettle 8. If your horse has health problems, your vet should find the cause before you choose a herb.
Are herbs for horses doping?
They can be. The FN (German Equestrian Federation) rules ban phytotherapeutics in competition in general 2. According to an FN vet, many herbs in feed are only ADMR-compliant up to 0.5 per cent per herb 10. The ADMR database is what counts 3.
What should I look out for with herbal mixes?
Read the full composition and check every ingredient before a competition. Pay attention to quality as well: since 2026, the EU has recommended monitoring herbs and compound feeds containing herbs for pyrrolizidine alkaloids 11.
Sources & studies
The content is based on the references listed below. It does not replace individual veterinary or feeding advice.
Show list of sources (11)
- Verordnung (EG) Nr. 767/2009Placing on the market and use of feed, labelling and claims; definitions of complete feed (Art. 3(2)(i)) and complementary feed (point (j)), content of feed additives (Art. 8), feeding instructions (Annex II No. 4). Link to the current EUR-Lex consolidated version (as of 26 December 2018).
- Deutsche Reiterliche Vereinigung (FN): Anti-Doping- und Medikamentenkontroll-Regeln für den Pferdesport (ADMR) mit Verbotsliste Anhang I–IIIRulebook with its own FN prohibited list (Art. 4.1). Annex II (prohibited medication, banned in competition) explicitly names “Harpagophytum Procumbens (Teufelskralle)” (devil's claw) under the musculoskeletal system and, under “Darüber hinaus sind verboten” (also prohibited), lists in general terms “Phytotherapeutika, wie z.B. Arnika, Ingwer” (phytotherapeutics such as arnica, ginger). Catch-all clause for substances with a similar structure or effect. Responsible persons are personally liable for everything administered to the horse (Art. 2.1.1), including with contaminated feed supplements (commentary on Art. 10.4). The document bears no date
- FN – Anti-Doping und Medikation (ADMR-Suchmaschine)Official database of the FN (German Equestrian Federation) on substances and withdrawal periods in competitive sport
- Axmann S, Hummel K, Nöbauer K, Razzazi-Fazeli E, Zitterl-Eglseer K (2019): Pharmacokinetics of harpagoside in horses after intragastric administration of a Devil's claw (Harpagophytum procumbens) extract. Journal of Veterinary Pharmacology and Therapeutics 42(1):37–446 horses in a crossover, Harpagophytum extract given intragastrically at 5 or 10 mg harpagoside per kg body weight; detectable in plasma for up to 9 hours. Pharmacokinetics only – no efficacy data
- Hackett ES, Mama KR, Twedt DC, Gustafson DL (2013): Pharmacokinetics and safety of silibinin in horses. American Journal of Veterinary Research 74(10):13279 healthy horses: 6.5 mg silibinin per kg body weight intravenously, orally in feed and by nasogastric tube. Then 5 horses given 6.5, 13 and 26 mg/kg twice daily for 7 days each. Oral bioavailability 0.6% in feed and 2.9% by tube, no accumulation, no dose-limiting toxicity. GGT slightly above the reference range in 3 of 5 horses at high doses. Healthy horses – no efficacy data for liver disease
- Menzies-Gow NJ, Banse HE, Duff A, Hart N, Ireland JL, Knowles EJ, McFarlane D, Rendle D (2023): BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction. Equine Veterinary Journal, doi:10.1111/evj.14009Veterinary guideline of the British Equine Veterinary Association with GRADE assessment. Section 3.6.6 and Table 10: chasteberry may improve individual clinical signs but has no demonstrated effect on ACTH. No benefit as an addition to pergolide. Evidence “Low”, recommendation “Weak”. The studies are small, without an untreated control group and with owner assessment; in a third study 13 of 14 horses treated with Vitex deteriorated
- Merck Veterinary Manual: Nutritional Requirements of Horses and Other EquidsSummary of the NRC recommendations: water requirement 5 litres per 100 kg body mass per day at maintenance, sweat losses of around 3.1 g sodium, 5.3 g chloride and 1.6 g potassium per litre, salt recommendation 1.6–1.8 g per kg feed dry matter at a maximum of 6% of the ration; from a 50% forage share potassium is adequately covered. Also covers the selenium requirement (0.1 mg/kg feed dry matter or at least 1 mg/day for a 500 kg horse, selenium as a component of glutathione peroxidase together with vitamin E) and the strong location-dependent variation of selenium in forage (grass forage on average 0.194 ppm, range 0–1.2 ppm); some regions are markedly low in selenium and may need supplementation. Also gives the iodine requirement (0.35 mg/kg feed dry matter, mares in late pregnancy 0.4), iodine poisoning of pregnant mares from around 40 mg/day, documented goitre cases in mares and their foals associated with large amounts of dried seaweed (kelp), that iodised salt easily covers the requirement, and that iodine supplementation is usually unnecessary except in severely iodine-deficient regions
- European Medicines Agency, HMPC (2010): Assessment report on Urtica dioica L., Urtica urens L., folium. EMA/HMPC/508013/2007Assessment report of 14 January 2010, section 2.1.1: nettle leaves contain minerals (ash approx. 17.9%; calcium as CaO approx. 5.9%; silicates 1–4% SiO2; high potassium content) and, in the stinging hairs, small amounts of acetylcholine, serotonin, formic acid and leukotrienes. Contact with the stinging hairs of the fresh plant can cause itching, dermatitis and urticaria (3.3.2). Preparations are considered well tolerated. Human medicinal context; check newer revisions if necessary
- FEI (2024): 2025 Equine Prohibited Substances List. Fédération Équestre Internationale, Lausanne, Stand 25.11.2024Version checked: 2025 (the 2026 version could not be accessed on 18 October 2026). Harpagoside is listed as CONTROLLED (analgesic), valerenic acid as CONTROLLED, capsaicin as BANNED. Silibinin/silymarin, Vitex constituents (agnuside, casticin), nettle, rosehip and ascorbic acid are not listed by name. Catch-all clause: substances with a similar chemical structure or similar biological effect are also prohibited. The list is revised annually; the current version always applies
- Joschko L (2023): Fairer Sport – Risiko unbewusstes Doping. Pferd und Mensch (FN-Magazin) 04/2023FN (German Equestrian Federation) members' magazine with an interview with Dr Michael Mäule: devil's claw is “fundamentally not ADMR-compliant” and has “a withdrawal period of four days”. Herbs acting on digestion or the airways (examples fennel, ribwort plantain, chamomile) are also often ADMR-relevant. In feeds, a limit of 0.5% per herb often applies. Secondary source (interview); the ADMR database is authoritative
- Empfehlung (EU) 2026/1210 der Kommission vom 9. Juni 2026 zur Überwachung des Vorkommens von Pyrrolizidinalkaloiden in Futtermitteln. ABl. L 2026/1210 vom 10.06.2026Recitals: all animal species are susceptible to acute and chronic PA poisoning; horses and rabbits may be more exposed because of high lucerne intake; the risk in the EU is generally considered low. Member States are to monitor, among other things, grass silage, hay, dried forage (lucerne, sainfoin), herbs and herbal extracts from PA-containing plants and compound feed containing herbs; 27 PAs including senecionine; limit of quantification 10 µg/kg; results to EFSA by 30 June 2028. Content checked via the BOE copy of the Official Journal (Spanish version)