All Laminitis is Not the Same

Researchers used two experimental models of laminitis, administration of bacterial endotoxin and administration of black walnut heartwood extract, to compare white blood cell responses and enzyme activity between skin samples and samples from the laminae. A mild degree of laminitis was induced in two groups of horses. A third served as a control.

Circulating white blood cell counts decreased in horses receiving both experimental treatments. With the black walnut model, enzyme activity was significantly increased in both skin and laminar tissues. Similar effects were not seen with the endotoxemia model. However, gene expression was significantly lower in both skin and laminar tissues with the endotoxemia model. 

These results support the concept that venous disturbances contribute to the laminitis process. They also suggest that a generalized disruption of physiologic processes affects both the skin and laminae of horses with some types of laminitis. The authors believe that as understanding of these processes improves, the microscopic examination of skin biopsies, which are relatively simple to perform, could become a useful tool for managing acute cases of naturally occurring laminitis.

—Riggs et al. AJVR 2009;70:1383-1390.

Thyroid Drug May Prevent Laminitis

Insulin and glucose dynamics are well recognized factors associated with some forms of laminitis, particularly grass founder. In an experimental study, 24 horses were pretreated with a thyroid supplement — dexamethasone or a placebo — then challenged 2 weeks later with a dose of endotoxin to simulate what happens during a spring-grass founder event. Glucose tolerance testing…