Horses respect and ignore debug fences at will

Zasz_Zerg​ if you want them to work like a regular fence, you could try adding an existing fence from the game around it to act as a barrier. Look for one of the invisible or thin line fences so you can't see it. Or go for the hedge fencing maybe, that's what I usually use. 

Debug fences are working as designed because they aren't included in routing data. They were never intended to be used as functional assets and are just set dressing.