They served as cavalry on various worlds in areas where AT-RTs or personal walkers were impractical. Blurrgs were capable of mowing down dozens of battle droids with a single charge. They were standardly equipped with flamethrowers and helmets.
Clone troopers from Lightning Squadron first encountered blurrgs when working alongside the Twi'lek freedom fighters during the Battle of Ryloth. At least one clone rode a blurrg into battle because his AT-RT broke down right before the attack on Lessu.