Here are two very powerful working dogs breeds: The Newfoundland and the Rottweiler.
Some authorities lay claim he is descended from Great Pyrenees dogs brought by Basque fishermen to the coast of Newfoundland; others consider his ancestors are French Boarhounds. An exceptionally powerful swimmer, it has saved many shipwrecked individuals from drowning. Strength is his trademark, together with a funny rolling gait. The body is strongly built and well-boned, the forelegs straight, the hind legs brawny and well-muscled. The head is massive having a broad skull, the muzzle broad and deep, eyes dark and deep-set, and small ears set well backand lying near the head. The tail drops straight or with a slight curve, while the coat is quite heavy and weather-resistant.
WEIGHT: 100-150 pounds
HEIGHT: 26-28 inches
COLOR: black, or white and black (Landseer).
When Roman legions got across the Alps almost 2,000 years ago, they employed this breed's Mastiff-type ancestors as guards and cattle drovers. In timethese dogs spread out across the Alps into the southern German village of Rottweil, where they were developed with local dogs to create the Rottweiler. For centuries thenceforth, this robust dog drove cattle to market and functioned as a guard and police dog. Its a stockily built, strong animal, calm and quiet. Its back is short, broad and level, his chest spacious, legs straight, with muscular thighs and quite heavy boned. The head is broad between the ears, with muzzle about as long as the depth of the skull. Its almond-shaped eyes bear a good-humored expression, while its small ears hang flat. The coat is short but really dense and hard.
WEIGHT: 85-110 pounds
HEIGHT: males 24-27 inches; females 22-25 inches
COLOR: black with rust to mahogany markings.