This Thorobred gelding developed a nasty case of hoof canker (cancer) in the 2004--2005 Winter.  Both of his right feet developed these painful cancerous growths that were extremely stubborn; they couldn't just be cut off because they had nerves and a very good blood supply.  He was constantly stepping on them and causing them to bleed and get sore.  The condition was caused from standing in a urine and rain soaked pasture with no drainage.  It took about 6 months for the growths to subside.  The next year I fully padded him with frog-support pads, impression material and copper sulfate to keep anything from growing under the pad.  He stayed sound all winter and now has a dry home for the winters.

The veterinarian treated it as in anaerobic bacteria, but I knew it was Hoof Canker--nasty stuff.  This horse was easy to shoe until he acquired these growths.  The clients treated him with caustic solutions that burned for several months, and he began to dislike having his feet picked up.  He's still hard to shoe to this day.  He's getting older, but the behavior problem while shoeing started when he developed these growths.  Poor guy....

See the written description of the disease below:

The following quotations are taken from The Principles of Horseshoeing (P3), by Doug Butler, Phd, CJF, FWCF, and coauthored by Jacob Butler, CJF, page 519, Chapter 39: Diseases of the Horse's Foot

"Canker, unguilysis, or hoof cancer, is a chronic hypertrophy (vegetative growth) or pododermatitis of the sensitive frog.  Rarely, the sensitive sole is also affected.  The frog has a ragged and oily appearance.  The frog grows so out of shape that it appears neoplastic (tumorous).  There is no longer a clear demarcation between sensitive and horny frog.  The loosely organized keratinized cells look like disconnected finger-like projections."

"Hoof cancer is caused by constant contact of strong ammonia compounds.  These substances irritate the sensitive structures and cause benign and possibly malignant growths to be produced.  Prevention consists of regular stall and hoof cleaning."