Objective assessment of gait in xylazine-induced ataxic horses.
Authors: Nout-Lomas Y S, Page K M, Kang H G, Aanstoos M E, Greene H M
Journal: Equine veterinary journal
Summary
# Objective Assessment of Gait in Xylazine-Induced Ataxic Horses Poor inter-observer reliability with the modified Mayhew grading scale has long hampered objective evaluation of equine neurological gait abnormalities, prompting Nout-Lomas and colleagues to investigate quantifiable gait parameters in horses developing dose-dependent ataxia following xylazine administration. Eight Arabian horses underwent comprehensive gait analysis on an equine high-speed treadmill (both level and 10% decline) and over ground using kinematic data from accelerometers placed on the head and sacrum, alongside kinetic data from force plate measurements, with assessments performed before and after low and high doses of xylazine. All horses developed significant dose-dependent changes in stride mechanics: stride time, stride length, and contact time all increased substantially (P<0.0001), whilst stride frequency decreased (P<0.0002); pelvic acceleration in the mediolateral direction increased on the treadmill but decreased over ground (P<0.05), and both centre of pressure and path length indices shifted significantly (P<0.05). Whilst the study is limited by its use of a single breed, skin-mounted accelerometers prone to artefact, and the brief pharmacological window of xylazine's effects, the findings suggest that objective kinematic and stabilographic parameters warrant further investigation as tools to supplement subjective neurological grading and potentially improve consistency in detecting clinical neurological disease. For practitioners involved in lameness assessment and neurological work-ups, these measurable gait variables—particularly stride dynamics and postural stability indices—represent a promising avenue toward more reproducible, evidence-based evaluation of ataxia.
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Practical Takeaways
- •Objective gait analysis tools (accelerometers, force plates, high-speed video) can reliably detect and quantify neurological ataxia in horses where subjective grading scales show poor observer agreement
- •When assessing ataxic horses, expect dose-dependent changes in stride characteristics—increased stride duration and length with decreased frequency—regardless of underlying cause
- •Ground-based assessment may reveal mediolateral stability changes not apparent on treadmill analysis; use multiple assessment conditions for comprehensive neurological evaluation
Key Findings
- •All horses developed dose-dependent ataxia following xylazine administration with increased stride time, stride length, and contact time (P<0.0001) and decreased stride frequency (P<0.0002)
- •Pelvic acceleration in mediolateral direction increased on treadmill but decreased over ground following xylazine administration (P<0.05)
- •Centre of pressure and path length indices changed significantly post-xylazine (P<0.05), some in dose-dependent fashion
- •Objective gait parameters including kinematic and stabilographic variables are more sensitive and reliable than subjective visual assessment using modified Mayhew grading scale