The bullmastiff is a large breed of domestic dog. It has a solid build and a short muzzle. It was originally developed by 19th-century gamekeepers to guard estates. The Bullmastiff was a cross of 40% Old English Bulldog (not the short, chubby Bulldog of today) and 60% English Mastiff for its size, strength and loyalty. They bark much less often than other breeds; however, they will bark on alarm.