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Heart-bar horseshoes that incorporate an adjustable pressure screw are used as a reversible model of hoof pain for experimental studies of anti-inflammatory medications. In this trial, researchers applied heart-bar shoes to five mares. They measured three biochemical markers for inflammation in the bloodstream, as well as dorsal coronary band temperature, before and after the shoes were adjusted to create a Grade 4 lameness (obvious at a walk, AAEP scale 0-5) to determine the role inflammation plays in this model of hoof pain.

The shoes easily produced the degree of lameness, but given the large amount of variation in the blood parameters measured relative to the effects of the shoes, the study was unable to detect a difference in any of the circulating markers for inflammation. Coronary band temperatures were higher in treated feet compared with controls following the creation of the lameness and after 1 hour, but no difference was detected after 3 or 13 hours.

The authors acknowledged inflammation can’t be ruled out as the mechanism of action. However, despite the presence of pain, increased temperature and loss of function they also suggest the experimental frog pressure model produces mechanical rather than inflammatory pain.

— Brunner TJ et al. JEVS 2020; in press