agreed ... dominance or 'pecking order' is a natural thing that you actually don't want to avoid .... if neither bull has the gumption to want dominance, then neither may be worthy of their duties ... 

allowing enough area for the non-dominant one to 'escape' or 'relinquish' is key ... usually it's gonna take at least a couple hundred yards if they are both 'manly', even though their physical statures might be skewed in favor of the older of the two.   ..... if the area is too small, they will fight every day because the non-dominant, but still 'manly' one, isn't allowed the ability to 'relinquish' or 'honor' the area that the dominant one 'reigns' over ....   

Any and every time multiple mature bulls are gathered into a small area, even after being pastured together in a large enough pasture for them to co-exist, they will fight, not because they don't recognize the dominant one, but because they aren't allowed to 'honor' his dominance by showing him the respect of keeping their distance, that's why it's important to pay attention when trailering mature bulls together or the trailer could be destroyed (either don't give them any room to fight -- or don't haul them at the same time)

the exception to this is when one bull isn't 'manly' and becomes completely submissive -- then the fighting is eliminated and the submissive bull won't ever challenge the dominant one for anything including breeding duties.