Persistent digital hyperthermia over a 48 h period does not induce laminitis in horses.

The research article indicates that a persistent increase in the temperature of a horse’s hoof, induced by administering a vasodilator, over a 48-hour period does not cause laminitis, in absence of an elevated insulin level. This suggests that although such heat increase may be involved with laminitis, it is not the only factor.

Objective of the Study

• The prime objective of the study was to ascertain whether a chronic increase in the temperature of the horse’s hoof, otherwise known as persistent digital hyperthermia, is the main factor responsible for causing laminitis, a disease characterized by inflammation of the laminae in horse’s hooves.

Methodology

• In order to promote persistent digital hyperthermia, the potent vasodilator, ATP-MgCl(2) was continuously infused into the distal phalanx (the last bone in the hoof) in the left forefoot of six Standardbred racehorses for a duration of 48 hours. This process was done via intraosseous infusion.
• As a form of internal control, the right forefoot of each horse was infused with a saline solution.

Observations and Results

• Lameness, a clinical sign of laminitis, was not detected at any examined interval (0h, 24h, & 48h) post-infusion.
• The hoof wall temperatures in the treated left forefoot (29.4 ± 0.25°C) were significantly higher (P<0.05) than in the saline-infused control right forefoot (27.5 ± 0.38°C).
• The horse’s serum insulin (15.0 ± 2.89 μIU/mL) and blood glucose (5.4 ± 0.22 mM) concentrations remained unchanged throughout the experiment.
• Post-experiment histopathological examinations, utilized to assess the occurrence of laminitis at a microscopic level, did not reveal any visual or microscopic signs of laminitis in any of the horses.

Conclusion

• Based on the findings, it was concluded that an increase in digital temperature up to 30°C over a span of 48 hours did not induce laminitis, at least not in the absence of hyperinsulinaemia (excessively high insulin levels).
• Therefore, while digital hyperthermia may contribute to the occurrence of laminitis, it cannot be considered as the sole mechanism triggering the disease, suggesting that other factors must also be involved.