EVIDENCE FOR HOOF ANGLES

Equine coffin bones remodel over time to match the angle of trim applied to the keratinous hoof wall in which they are enclosed, so that a measurement of the angle of the fore face of the coffin bone can be assumed to be very close to the angle of the external hoof at the time of death.

Ethan Allen presents quite low angles of 42.5 and 45 degrees, fore and hind respectively. This might have been due to neglect, i.e., letting the feet grow out and the heels run under through infrequent or improper trimming. I think it was more likely deliberate, however, as a well-known technique for increasing a trotter’s knee and hock “action” is to lower the hoof angles. The Schreiber & Sons photo which we have of Ethan Allen was taken in 1859 when the stallion was 10 years old and in the prime of his racing career; magnification shows that his hoof angles were in the 50-degree range at that time and he stood on plenty of healthy heel. After being moved at the age of 22 to the Kansas stock farm, Ethan Allen was frequently exhibited both in hand and in harness but not actually raced, and my surmise is that Sprague and Akers were more interested in presenting him as a flashy mover than as a fast one.

The fore faces of Lexington’s coffin bones are obviously much steeper than Ethan Allen’s: about 55 degrees in front and 57 in back, a little steeper than average for domestic horses but very appropriate for a horse whose job is to race cross-country. More importantly, the projected hoof angles match the horse’s pastern conformation.

Unfortunately, it is not possible to precisely measure Black Hawk’s hoof angles from the available close-up photos, which were not taken from the side; I estimate them to be lower than Lexington’s but higher than Ethan Allen’s, in the 50-degree range which is the

average for domestic horses.

Rolf’s coffin bones are good examples of asymmetry—it is in fact rare for the left and right forefeet of any horse, wild or domestic, to exactly match, but Rolf’s difference is outside normal limits. While Rolf’s left and right hind coffin bones present identical angles, the right fore coffin bone is about 7 degrees steeper than the left. It is also markedly smaller and narrower; this is what horsemen refer to as “clubfoot.” This condition is not congenital in horses but instead develops gradually as an accompaniment to the horse’s habit of putting more weight on the opposite forefoot. This habit may have its roots in the dam’s permitting the foal to suckle from only one side, but it can also be a response to pain in the smaller, steeper foot. Rolf’s arthritis and ringbone as well as his navicular “changes” are much more marked on the right fore.