The induction of equine laminitis with an aqueous extract of the heartwood of black walnut (Juglans nigra).

The study reports on the effect of an extract from black walnut (Juglans nigra) heartwood on the development of horse laminitis, finding that horses developed the condition within 12 hours of ingesting the extract. While an ingredient, juglone, was identified in other parts of the walnut, it was not present in the heartwood extract, suggesting other causes for laminitis.

Methodology and Results

• The research involved experimentation on 10 horses wherein they were orally administered an aqueous extract of the heartwood of black walnut.
• Following the administration, Eight out of the total number exhibited symptoms of Obel grade 3 or 4 laminitis within a 12-hour period. Apart from laminitis, signs of limb edema and mild sedation were also observed among the horses. These were the only clear-cut clinical indications of the effect of the extract.
• Due to severe signs of the illness, one of the horses was euthanized. The other seven recovered from the condition within 6 days, indicating that while the extract induced laminitis, the effects were not long lasting or lethal in all cases save one.

Nature of the Extract

• Gas chromatography/mass spectrometry was employed to identify the chemical composition of the aqueous extracts of the heartwood, the bark, and the nuts of black walnut.
• Through this analysis, the substance juglone was detected in the bark and the nuts of the walnut, but not in the heartwood. As the heartwood extract was the substance given to the horses and not the bark or nuts, it was concluded that juglone could not have been the factor causing laminitis in the horses.

Conclusions

• The conclusion drawn from this research is that an aqueous extract from black walnut heartwood is a cause of laminitis in horses. However, juglone, an ingredient previously considered potentially responsible due to its presence in other parts of the walnut, was not found in the heartwood, leaving the reason for the laminitis causing properties of the heartwood extract unclear.
• This highlights the need for further research to determine the active ingredient or mechanism by which black walnut heartwood causes laminitis in horses.