@MightyMax I own a two years old New Zealand white. Fortunaly it only has a Hyperkeratosis Callus on the left hind leg. It's a week now that I apply daily some Aloe Gel on the callus and take him for a walk (some exercise). And I have moisture/water problems in his rabbit hutch (water spilling from his drinking bowl, raining, very high level humidity weather etc...) and sometimes I am not so attentive and he may find some thorns in his beddings. I only hope he doesn't have one stuck in his leg or even worse that it might be an urine scald.
@Jack's-Jane First three links aren't working on my mobile. I agree I shouldn't apply daily Aloe Gel as the callus seems to be growing larger due to excessive moisture. Maybe only apply twice a week as the skin from a dark grey color after the application of the Aloe Gel seems to have changed to a healthy pink color?
Thank you so much for the very interesting links especially the one with the picture/grading in it.