L-Tryptophan

Trp · essential amino acid

Mechanism

L-tryptophan is the metabolic precursor of the neurotransmitter serotonin (5-HT), which is attributed a mood- and arousal-modulating role. The rationale behind calming products is that increased tryptophan intake raises central serotonin synthesis. Evidence in the horse is inconsistent, however: Bagshaw et al. (1994) and Noble et al. (2008) found no consistent calming effect with oral dosing, and some studies even described mild excitation at low doses. A reliable sedative effect in the horse is therefore not established. Important for competition: L-tryptophan is currently not on the FEI Equine Prohibited Substances List, but the status of related calming-active substances changes continually.

Cautions

· Effect in horses not reliably established; contradictory study data
· High oral doses: literature reports possible adverse effects (incl. ataxic/excitatory reactions)
· FEI: currently not listed, but check the status of calming-active substances before competition

Sources

PMID:18537776Noble et al., Equine Vet J 2008 — Tryptophan & behaviour

Bagshaw 1994 Appl Anim Behav SciBagshaw et al. — Tryptophan effects in horses

FEI EPSL 2024FEI Equine Prohibited Substances List 2024

Equiterna Score

58/100

solid

Science4.5/10

Practical experience6/10

Safety7.2/10

Overall score scale

high overall75–100solid55–74limited0–54

How the Equiterna Score is built

The Equiterna Score combines three dimensions into a value of 0-100: science (40%), practical experience (30%) and safety (30%). It is transparently derived from evidence level, attributed sources (PubMed/journals), legal classification and cautions. The FEI doping status is shown separately as a competition-law note and does not enter the score. Commissions and vendor relationships have no influence on the score. In addition, the editorial safety rating caps the result: it limits the safety dimension and the overall tier (orange: at most solid). For entries rated red, no score is calculated at all. The rating never raises anything — a green rating does not lift a calculated value.

An editorial assessment of the evidence and safety situation — not a healing claim and not an individual recommendation. It does not replace veterinary advice.

DosageStudy reference range 0.1–0.2 g/kg BW/day orally; approx. 5–10 g/animal/day for a large horse (~500–600 kg) as a supplement. Discuss use with a vet.

AMG statusComplementary feed

FEI statusNot listed

SafetyVery safe

Pharmakas

Not orderable →

Knowledge connections

Related conditions

Nervousness & Stress →serotonin precursor; study evidence on calming is contradictory

Journal articles on this compound

Magnesium und Gelassenheit — zwischen Mythos und Evidenz →

All sources in the study library →

Usage note

This content is for information and education. It does not replace veterinary diagnosis or treatment. If your horse shows signs of illness, consult a veterinarian.

“Nothing forced can ever be beautiful.”

Xenophon · On Horsemanship (c. 365 BC)

Equiterna is an intermediary platform for equine knowledge, marketplace and tools — not a veterinary-medicines dealer, veterinary practice or pharmacy. Compound information is study-attributed and free of healing claims. Legal framework: Regulation (EU) 2019/6 / TAMG (DE/AT), Feed Regulation (EC) 767/2009, FEI Prohibited Substances List, HWG.