title: Randomised clinical trial on the effect of a single oral administration of l-tryptophan, at three dose rates, on reaction speed, plasma concentration and haemolysis in horses.
abstract: Tryptophan (TRP) is marketed as a calmative for horses despite reservations about its efficacy. The aim of this study was to measure the effect of oral TRP administration on the reaction speed of horses. Sixty mature horses were used in a two stage randomised, blind, cross-over study, receiving a placebo and an oral dose of TRP (30, 60 or 120 mg/kg body weight), before undergoing a reaction speed test. Blood samples were taken up to 96 h after TRP administration, to identify signs of acute haemolytic anaemia. Plasma TRP concentrations were increased (P <0.001) by the administration of TRP paste. However, TRP had no effect on the reaction speed of horses when startled. There was no evidence of alterations in clinical pathology parameters in 432 blood samples. While the safety of these doses of TRP can be confirmed, there was no evidence to suggest that a single dose of TRP is an effective calmative for horses.
authors.affiliation: School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia. Electronic address: gnoble@csu.edu.au.
authors.forename: Glenys K
authors.initials: GK
authors.lastname: Noble
authors.affiliation: School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia.
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia.
authors.forename: Dagong
authors.initials: D
authors.lastname: Zhang
authors.affiliation: School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, 4001, Australia.
authors.forename: Martin N
authors.initials: MN
authors.lastname: Sillence
mesh_terms: D000284:Administration, Oral; D000818:Animals; D018687:Antidepressive Agents, Second-Generation / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood* / Q000493:pharmacokinetics; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D006461:Hemolysis / Q000187:drug effects*; D006736:Horses; D008297:Male; D013216:Reflex, Startle / Q000187:drug effects*; D014364:Tryptophan / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood* / Q000493:pharmacokinetics
chemical_list: D018687:Antidepressive Agents, Second-Generation; D014364:Tryptophan
keywords: Behaviour; Equine; Randomised clinical trial; Reaction speed; Tryptophan