The bear would be very fast and much more powerful than the horses or camels (having claws and very sharp teeth) so the bears could be taught to fight along with their rider . Of course , if you ever have to face an elephant in combat , your bear and you are gone ( see this ). But otherwise , the bear would be a feasible choice for combat . To feed them , you would need fish or meat which is costlier than grass/hay which you could use to feed horses . This means the bear would be more expensive to keep. This would mean that bear cavalry would be less preferred than horses / camels . Bears are quite fast , being able to outrun a racehorse for short distances , but cannot endure at such speeds for very long (source http://www.bearsmart.com/about-bears/general-characteristics/ ) .Hope I helped !

The bear would be very fast and much more powerful than the horses or camels (having claws and very sharp teeth) so the bears could be taught to fight along with their rider . Of course , if you ever have to face an elephant in combat , your bear and you are gone ( see this ). But otherwise , the bear would be a feasible choice for combat . To feed them , you would need fish or meat which is costlier than grass/hay which you could use to feed horses . This means the bear would be more expensive to keep. This would mean that bear cavalry would be less preferred than horses / camels . Bears are quite fast , being able to outrun a racehorse for short distances , but cannot endure at such speeds for very long (source http://www.bearsmart.com/about-bears/general-characteristics/ ) .Hope I helped !

EDIT - Another problem is - BEARS HIBERNATE! . So , if war breaks out in winter time , when your bear cavalry is hibernating , better have backup ! This probably means bears can only be troops in summer and definitely not your primary cavalry .