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Background. To gain a greater insight into normal and laminitic hoof growth and to be able to make comparisons between the two groups.
Methods. Ten normal and three laminitic equines completed the survey, each hoof was marked with a horizontal file mark in three places, the dorsal wall and each medial and lateral quarter at about 1cm below the coronary band. Measurement of the progression of the file mark was made every 28 days, a total of 1,872 measurements were made.
Results. Equine hoof growth rates showed seasonal variation with greater rates of growth during the summer months and slower rates during the winter. In normal horses growth was slower at the quarters compared to the dorsal region but the difference was not statistically significant (p>0.05).
During the summer months laminitic hoof growth at the quarters was significantly faster than at the laminitic dorsal region (p< 0.05). The rate of accelerated growth at the laminitic quarters reduced during the winter months and was not statistically significant (p>0.05).
Discussion. The results of this measurement survey highlighted that laminitic hoof growth is remarkably different at the quarters. This raises the question of when the transition from normal to laminitic hoof growth takes place. Traditionally changes in hoof shape during laminitis have been assumed to be a consequence of the acute phase but this has never been confirmed. The possibility exists that abnormal hoof growth could commence early in the developmental phase, the implications of abnormal hoof growth commencing at this stage are profound. A new etiology for equine laminitis then becomes possible, based on accelerated hoof growth at the quarters inducing the hoof capsule to change in shape; this process would have the capacity to subject the underlying dorsal dermal laminae to forces of extension which would be capable of destroying the laminal interface.
1. The spelling in the title & text has been changed from etiology to aetiology.
2. My address has been shortened.
3. New text has been added from line 180 to 189, as follows:- 'In a recent study, a correlation between dorsal hoof wall curvature and cell proliferation in epidermal papillae at the quarters was revealed, indicating that there may be a difference in the overall growth rate between the various capsular shapes. Further analysis showed that there was a regional variation of cell proliferation between the epidermal dorsal and quarter coronary regions. Cell proliferation increased at the quarters as a function of the hoof curvature (i.e. for dished hooves) but no variations were noticed at the dorsal regions whatever the dorsal curvatures involved. The same study also measured the fluorescence intensity of the cell proliferation marker Ki-67 and cytokeratin protein K14, which revealed clear response with an increased expression of Ki-67 and K14, as a function of time and insulin concentrations (Al-Agele 2018).'