A randomised, blinded, crossover study to assess the efficacy of a feed supplement in alleviating the clinical signs of headshaking in 32 horses.

This research paper demonstrates that a feed supplement offered no enhanced benefit over a placebo in alleviating the clinical signs of headshaking in horses. However, a significant placebo effect was reported, emphasizing the importance of well-executed, randomized controlled trials to accurately evaluate treatment effects in animal trials.

Objective and Methodology

• This research aimed to assess the efficacy of a feed supplement in alleviating the clinical signs of headshaking in horses through a randomised, blinded, placebo-controlled trial.
• 44 horses with a previous diagnosis of chronic idiopathic headshaking were involved in a crossover design study, meaning they received both the supplement and a matching placebo, taken orally, over a span of 28 days with a 14-day washout period between treatments.
• Video recordings of the horses were taken at rest and during exercise both before the trial and at the end of both treatment periods in order to assess the degree of headshaking.
• Two independent veterinary surgeons assessed the degree of headshaking in a randomized, blinded manner.
• To provide a subjective assessment of the headshaking signs, a questionnaire was given to the horse owners at the beginning and end of each treatment period.
• A mathematical tool known as the Wilcoxon signed rank test was used to compare the scores determined while the horses were on the supplement and the placebo.

Results

• As per the video assessments, no substantial difference was found between the scores for the horses while they were on the supplement compared to the placebo.
• The owner questionnaire responses likewise showed no significant differences between scores for any activity when the placebo and supplement were compared.
• However, both placebo and supplement were reported to significantly improve symptoms during all activities compared to pretreatment scores, as per the owners.

Conclusion

• The study concludes that the supplement did not offer superior advantage over the placebo in reducing the clinical manifestations of headshaking in horses.
• However, a substantial placebo effect was reported, indicating that horse owners perceived an improvement in their horses’ symptoms regardless of whether they were given the placebo or the supplement.
• This study demonstrates the vital importance of properly implementing randomised, blinded controlled trials to accurately determine the effectiveness of treatments in animal trials.