A randomised, blinded, crossover study to assess the efficacy of a feed supplement in alleviating the clinical signs of headshaking in 32 horses.
Authors: Talbot W A, Pinchbeck G L, Knottenbelt D C, Graham H, McKane S A
Journal: Equine veterinary journal
Summary
# Editorial Summary: Feed Supplement Efficacy in Equine Headshaking This rigorous randomised, blinded, crossover trial enrolled 44 horses with chronic idiopathic headshaking to evaluate whether a commercial feed supplement could reduce clinical signs of the condition; horses received both active supplement and matched placebo for 28-day periods separated by a 14-day washout, with objective assessment via blinded video analysis and subjective evaluation through owner questionnaires at baseline and endpoint. Video analysis by two blinded veterinary surgeons revealed no statistically significant difference in headshaking severity between supplement and placebo treatments (P = 0.7), and owner questionnaires similarly showed no meaningful distinction between the two interventions across any activity measured. Whilst this negative finding is itself important, the study identified a substantial placebo effect: both groups showed significant improvement compared to pre-treatment baseline scores when assessed subjectively by owners, despite objective video analysis failing to confirm this benefit. For practitioners advising clients on headshaking management, these results suggest that apparent clinical improvements attributed to oral supplements may reflect owner expectation bias rather than genuine therapeutic effect, emphasising the need to counsel clients realistically about the limitations of feed-based interventions and to pursue evidence-based diagnostic and management strategies for this notoriously difficult condition.
Read the full abstract on PubMed
Practical Takeaways
- •This particular feed supplement has no proven efficacy for headshaking when objectively assessed—owners perceiving improvement should recognize this may be placebo effect rather than true therapeutic benefit
- •Be cautious when clients report improvement in subjective conditions like headshaking; always use objective measures when possible, as expectation bias significantly influences owner perception of treatment success
- •Recommend evidence-based therapies with rigorous trial data rather than unproven supplements, and manage client expectations by explaining the placebo effect
Key Findings
- •Video-based blinded assessments showed no significant difference between supplement and placebo (P = 0.7)
- •Owner questionnaires showed no significant difference between supplement and placebo for any activity
- •Both supplement and placebo groups showed significant improvement compared to pretreatment scores based on owner perception
- •A substantial placebo effect was demonstrated, highlighting the importance of controlled trial methodology in equine research