Giant schnauzers are a large dog breed from Germany used for herding and farm work. Breed standard for giants recognizes two coat colors, solid black and a combination called "pepper and salt" that appears gray. Other tones in a black coat, including a reddish tint, are undesirable.
A black giant schnauzer must be solid, rich black. A white mark on the chest is acceptable, but any other white is disqualifying in the show ring. A mixture of gray or tan hairs also is undesirable. A giant's undercoat should also be solid black. Some black giants have a reddish tint in their hair.
Black giant schnauzers sometimes have fading or burning of their coat that creates a reddish appearance. This red tint can be caused by long-term exposure to the sun, extensive swimming in chlorinated water or old age. Undercoat that appears red can be removed by "stripping," a special grooming technique.
Giant schnauzers first bred in Germany actually came in a wide variety of coat colors, including red, brown and yellow. Old portraits of German royalty show giants with red coats. These coat colors are rarely seen today and are not breed standard. Achieving a total black coat, with no undercoat of tan or brown, was a challenge for the developers of the giant schnauzer.
Dogs with black coats can carry a brown recessive gene. Both parents would have to carry the recessive brown gene, which may give their offspring's coat a reddish tint. Two brown-based dogs that are bred create a double recessive gene, which overrides a pure black coat. The brown, or reddish, gene can be carried for many generations before showing up in a litter.
Diet can affect a giant schnauzer's coat color, says Cynthia Fiorino, a longtime breeder of champion giant schnauzers and past president of the Giant Schnauzer Club. "Years ago, we switched brands of dry food and found it turned our giants reddish. We talked with the manufacturer and found that other owners of black-coated dogs had similar experiences."