This pic looks intriguing in the way it shows a male animal being branded on the buttocks. The men are ranchers and would being doing this normally to cattle or other livestock. What sums this up: this male is treated as livestock and an animal.
Biologically, it is doubtful the human buttock could be branded in this manner. The skin layers and fat composition make the male buttocks unsuitable. I have not seen it happen or if this manner of branding would work. Would be interesting to find this out and do some research. If it is feasible I would not hesitate branding my slave or slaves in such a manner.