He's pretending to be a farrier... The rest of the story behind this famous farrier painting:
Edwin Landseer's painting Shoeing The Bay Mare was a commission from Jacob Bell, a man Landseer had known since art school and the owner of a pharmaceutical company. The basis of their friendship was a mutual fondness for animals. From time to time the artist borrowed Bell's animals to use as models; his favorite bay mare Betty, or one of his bloodhounds. Bell waited nearly 10 years for the portrait he had wanted of Betty with her foal. But by 1844, when Landseer got around to painting her, the mare had produced two foals, both long gone from Bell's barn, and had come to be called Old Betty. So Landseer decided on a shoeing scene, and painted Bell himself as the farrier.
In the corner we see Bell's bloodhound, doing as all dogs do - eating hoof. It's a lovely scene on many levels, and the farrier community is fortunate that Landseer put off painting the picture of Betty until he did - otherwise we'd be looking at a mare and her foal and NOT this well done farrier picture. (even if the farrier IS an imposter!)
This Landseer image is also featured on Golf Shirts here, Business Card here and Invoice Pads here.