The Bullmastiff is a powerful dog, said to be a cross between the Mastiff and the Bulldog. Originally bred to find and immobilise poachers, the breed has proved its value as a family pet. Large, by family standards, the dog weighs 115 to 135 lb (52 to 61 kg), at 30 inches (762 mm) tall, with the bitch 20 to 30 lb (10 to 15 kg) lighter and 3 inches (76 mm) shorter. They make good parents, and often exceed 6 in a litter.
With its handsome, powerful appearance and superb speed coupled with strength and endurance it can overtake and capture intruders without mauling them. These traits make the bullmastiff appear to be an excellent choice for a guard dog; however, a stubborn streak makes the animal resistant to obedience training and overly protective of its human family. Due to this, the breed has been overtaken by others, more popular as guard dogs.
Courtesy of: The Free Dictionary