The lipopolysaccharide model for the experimental induction of transient lameness and synovitis in Standardbred horses.

This research examines the accuracy of a lipopolysaccharide (LPS) model to cause temporary lameness and joint inflammation in Standardbred horses, and it aims to establish the precise amount of LPS needed to induce such conditions. It also explores the timeline of the induced lameness and how it can be prevented through pre-treatment with anti-inflammatory drugs.

Objectives and Methodology of the Study

• The study primarily sought to establish the exact dosage of LPS from a specific strain of E. coli (referred to as O55:B5) needed to cause mild to moderate lameness after being injected into a Standardbred horse’s middle carpal (a significant joint in a horse’s forelimb).
• Eight healthy Standardbred horses were initially used in a structured trial that began with a dosage of 10 endotoxin units (EU) of LPS. The level of lameness was determined visually as well as quantitatively using advanced technology (an inertial sensor system and pressure plate analysis).
• Besides observing lameness, the study also assessed the fluid within the horses’ joints for total cell counts, protein levels, and the presence of the inflammatory mediator named prostaglandin E (PGE).
• After a two-month break, the same dose of LPS that proved effective in causing lameness was then used in an experiment to understand the effect of an anti-inflammatory drug called meloxicam. The analysis included repeated measurements and took into account the possible variation among individual horses.

Findings of the Study

• At a dosage of 10 EU LPS, the desired level of lameness was achieved in the preliminary trial. The peak lameness occurred four hours after injection, followed by a rapid decline and eventual return to normalcy within 48 hours post-injection.
• On the other hand, pre-treatment with meloxicam prevented any lameness after LPS injection.
• The PGE levels were significantly higher at the eighth hour and 24th hour post-injection during the baseline trial compared to when horses were pre-treated with meloxicam.
• In summary, injecting a Standardbred horse’s middle carpal joint with 10 EU LPS causes mild temporary lameness and joint inflammation. However, these outcomes can be mitigated if horses are pre-treated with meloxicam.