The Genetics of "Hairies"

By Linda Monroe

(Reprinted by permission of the author and the Mastiff Club of Victoria in whose newsletter it first appeared - Volume 6, #1, October 1995).

Some Mastiff pups are "fluffy" as pups, but shed this off as they get older, usually by six months or so. A true long coat stays long and gets even longer. Usually the coat is real soft and silky. Long fringe on the ears is usually a sign that a pup is actually going to be a long haired adult. The long coat gene comes from the other breeds used to save the Mastiff breed from extinction after WWII.

The gene for long hair is recessive, denoted as (l), and the short coat is dominant, denoted as (L). Both parents must be carrying the recessive (l) gene to produce a long-coated pup. The odds of having a long-coated pup in a litter out of two short-coated parents are 25%, if both parents are carrying the (l) gene. If you breed a long-coated bitch to a short-coated male who is also a (l) carrier, the odds of having long-coated pups goes up to 75%. If you breed her to a male that is (LL) or double dominant for short coat, none of the pups will have a long coat, but all will be carriers of the long-coat gene. The hard part is determining if the male is (LL), or (Ll).

If the male (or female) has ever thrown a "fluffy," then you know what they both are genetically. Of course, you will need more than one litter to determine this if you get all short-coated pups due to random selection. It is not possible to determine the actual coat length of a pup until approximately five weeks of age. I have seen "long-coats" that were huge and gorgeous and others that were small and not so gorgeous. The coat gene is inherited independently from most other characteristics, as is color.

Example:

Long-coat X dominant short-coat
    ll		LL		=  Ll  Ll  Ll  Ll

	(100% offspring short-coated, but carries long-coat recessively)

Short-coat w/recessive X short-coat w/recessive
    Ll			   Ll	=  LL LL Ll ll

	(25% long-coat; 25% long-coat carrier; 50% dominant short-coats)

Dominant short-coat X dominant short-coat
    LL			   LL	=  LL LL LL LL

	(100% of offspring will be short-coated)

Long-coat X long-coat
    ll        ll		=  ll ll ll ll

	(100% long-coated offspring)