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.

This study assessed the impact of oral Tryptophan (TRP) administration on horse behavior, particularly reaction speed, and found no evidence that a single TRP dose acts as an effective calming agent for horses.

Research Methodology

• The researchers utilized a two-stage randomized, blind, cross-over study design on sixty mature horses. This study design was intended to eliminate biases as the treatment was randomly assigned and neither the subjects (horses) nor the researchers knew which treatment was being administered (TRP or placebo).
• Each horse received a placebo and an oral dose of TRP at three different concentrations (30, 60 or 120 mg/kg of body weight) before undergoing a reaction speed test.
• Blood samples were obtained up to 96 hours following the administration of TRP in an attempt to detect potential signs of acute haemolytic anemia, a condition where red blood cells are destroyed faster than they can be replaced.

Research Findings

• Plasma TRP concentrations increased significantly following the administration of TRP paste. This demonstrated that the TRP dose had been absorbed and was available within the bloodstream.
• However, the administration of TRP had no discernible impact on the reaction speed of the horses when startled, implying that it does not act as a calming agent in the context of this behavior.
• No alterations in clinical pathology parameters were found in any of the 432 blood samples, implying that the administration of TRP did not result in any observable adverse health effects, such as acute haemolytic anemia.

Conclusion

• Despite Tryptophan (TRP) being marketed as a calmative for horses, the findings of this study offer no support for its efficacy in this role.
• The study confirmed the safety of these levels of TRP dosage, as no adverse health effects were observed, suggesting that TRP is safe for use in horses at the tested levels.