Quote:
Originally Posted by Breezeaway  It is the Merling gene that causes deafness and blindness in dogs. I bred australian shepherds, Breeding 2 dogs with the merle gene produces pups that are blind or deaf if they are born with a solid white head. The merle gene is not the same as the piebald gene. They dont have to be extreme white, Just an all white head to be deaf or blind. |
You're correct that the merle (or dapple) gene may cause deafness. It isn't the only coloring gene that does, though. Here's another quote from a previously posted link....."Double Dapple and Piebald Patterned Dachshund
Health Issues
As keepers of this breed, we are morally and ethically responsible for the health, welfare, and future of our beloved dachshund. With this in mind, the Dachshund Club of America (DCA) membership voted to remove the double dapple pattern from its revised Official Dachshund Standard (March, 2007), and to exclude the piebald as a new pattern, since our standard now calls for a small amount of white on the chest as acceptable, but not desirable. The exception is the single dapple (merle) pattern, where a large amount of white on the chest is acceptable.
The main reason – health problems which are detrimental to our breed.
Offspring from double dapple (merle x merle) and dapple x piebald breedings can be born:
• deaf, partially deaf
• blind, partially blind
• with no eyes
• sterile, impaired sperm production
Just as you, knowingly, should not breed any other health problem into your gene pool, you should not breed dapple to dapple or dapple to piebald. Generally, dappling is easy to discern since it can easily be seen with the naked eye. There are some coats, however, where the dappling is so minimal that just a few hairs are dispersed through the coat, some or all of which may be camouflaged. In addition, it is sometimes hard to differentiate a dapple pattern from a piebald because many of the patterns look so similar, especially to the untrained eye. Therein lies the problem – there are times when it is very difficult to classify merles from piebalds. (see below)
Double Dapple Dachshunds
Piebald Dachshunds
doubledapples
Throughout the world, over many years, there have been numerous scientific studies on double merle breedings, albeit, not only dachshunds but other breeds, as well. The fact that double dapples have health problems is well-established. In his book, Inherited Eye Diseases in Pure Bred Dogs (Williams & Wilkins, May 1989), the highly regarded veterinary ophthalmologist, Dr. Lionel Rubin, states, “Because of the extensive anomalies in the progeny, merle to merle breedings are to be avoided...” In Genetics of the Dog, Malcolm B. Willis, BSc, Phd. writes, “...the merle gene in dachshunds has not only revealed eye problems (Wegner and Reetz, 1975; Dausch et al 1977) but
piebalds
also impairment of sperm production (Treu et al 1976) and hearing problems (Reetz et al 1977).”
On the other hand, there have not been many (if any) lengthy studies done on piebalds, as yet. The piebald pattern carries a potential risk of health problems, specifically deafness. The research study regarding deafness to which The AKC Health Foundation issued a grant, indicates that increasing amounts of white in the coat increase the likelihood of deafness. Heather Pate, of DDEAF, Deaf-initely Dogs, the official newsletter of Deaf Dog Education Action Fund,
www.ddeaf.org, stated in the Spring 2002 edition: “Genes for coat color that are intricately linked to deafness are the merle genes and piebald genes. Merle genes produce the dappled or merle effect of multicolored individual hairs. Piebald genes affect the amount and distribution of white on the dog’s coat....” If our breed has increasing numbers of piebalds in its gene pool, it stands to reason that we will eventually have more deafness in our breed."...........With this in mind, I'll ask my original question again. What makes the Yorkie unique to other breeds as far as piebalds go? Piebald is piebald, no matter the breed and the potential health risks are real. Why, given that prospect, would someone knowingly breed for that trait?