Learn how hundreds of Civil War veterinarians cared for the millions of horses, mules, and camels required by the armies.
www.civilwarmed.org
This was very interesting, instead of individual instances, it seems to suggest that the army as a whole neglected the care of animals even when they attempted to make a department for it. Not exactly what you were looking for but maybe of some interest. Here is an extremely rare photo of a veterinarian's insignia. Farriers had a horseshoe insignia.
I don't have a source for this story, but supposedly Grant, while riding with his staff, came across a soldier who was mercilessly whipping a horse who was unable to pull a wagon that was overloaded. Grant had the soldier tied to a tree and flogged with the same whip he was using on the horse.