Black walnut (Juglans nigra) toxicosis: a model for equine laminitis.

This research investigated the effects of black walnut extract on horses, revealing it consistently and reliably induces laminitis, a serious and painful hoof condition, thus providing a clinical and pathological model for studying this disease.

Laminitis Induction

The research centered on inducing laminitis in horses to learn more about the disease. Laminitis is a painful and potentially crippling disease that affects the horse’s foot. The scientists administered extracts of black walnut, a known toxin to horses, by a nasal-gastric tube to provoke the condition.

• Twelve light horse geldings were subjected to this experiment, all of which developed laminitis within 8 to 12 hours after dosing.
• There were varying degrees of severity, with four of the twelve horses demonstrating Grade 3 laminitis, notable for a refusal to lift their feet and lameness even at a walk.

Associated Symptoms

Along with laminitis, the horses exhibited other symptoms that gave a more rounded understanding of the disease.

• Depression and limb edema (swelling generally due to excess fluid) were observed.
• There was no evidence of shock or colic, two conditions often associated with distress in horses.
• Horses had a decreased number of neutrophils, a type of white blood cells, to begin with, but this shifted to a relative increase 8 to 12 hours after dosing.
• Plasma levels of two hormones associated with stress, epinephrine and cortisol, increased slightly in highly affected horses.

Pathological Findings

Post-mortem study helped to shed light on the severe structural damage caused by laminitis.

• The severe laminitis was characterized by tissue death in the tips of certain structures within the hoof (dorsal primary epidermal laminae).
• A proliferative response was found in these tissues characterized by increased cell division and clustering of skin cells.

Conclusion

The study identifies black walnut toxicosis as a consistent and reliable model for inducing laminitis. This could assist in the study of the pathogenesis (development) and treatments for laminitis, helping to improve our understanding of this serious equine health issue.