What advantages would cattlebovines have over horses when used as cavalry?
I've got a culture whose way of life is based around cattle, and I'm wondering what kinds of advantages they might have in combat over traditional horse-based cavalry if they rode a breed of bovines specifically bred for fighting. I don't want to limit them to just what we think of as a standard 'cow', but would like them to have mounts that are at least something cow-like, such as buffalo, bison, or gaur.
The cow riders are a distinctive culture that focuses on nomadically ranging cows across a large area of wet forest and swamp across a wet basin on the interior of the continent, and they've been there long enough to have bred and trained some of their cowsanimals into mounts capable of running and fighting. They do, however, have access to horses, as these are raised by another culture that lives on the far side of one of the mountain ranges surrounding the basin in some drier coastal plains. What I'm wondering is whether or not there is a reason, besides the practicality of already having cowsthe animals around, that they would be used in combat.
Furthermore, if cows can be used to an advantage in combat over horses, what sort of role will they take on the battlefield, and how would using them as a primary cavalry mount change the way a culture conducts warfare? This isn't to say that the cowbovine riders don't have any horses, but merely that the majority of their cavalry does not use them. Should they be far superior in some role, such as perhaps being superior scouts as a result of being faster, horses would be used.
Do they have any such advantages, or would they realistically be replaced by horses for combat?