The bullmastif is the best guard dog.The Bull mastiff was first obtained by crossing 60% Mastiffs with 40% Bulldogs in the country of England. Mastiff Bulldog types can be found in records as early back as 1795. In 1924 Bullmastiffs began to be judged well. 3 generations of breeding of Bullmastiffs was required for Bullmastiffs to be registered as purebreds.
Male bullmastiffs grow to be 25 to 27 inches tall (63.5 to 68.5 cm) at the withers and 110 to 140 pounds (50 to 60 kg). Females typically reach 24 to 26 inches (61 to 66 cm) at the withers, and 100 to 120 pounds (45 to 55 kg).