130 replies to this topic

[workindogs]

I don't particularly care for white headed dogs ... never really thought about blue eyes and never had one. From my perspective, it would be very easy to simply not select a merle, white head or blue eyes. There may come a point where I am faced with a dilemma about white headed because it is much more common and might appear unexpectedly in a litter even in a breeding of apparent dark factored dogs. Don't get me wrong, I have no problem with breeding a white factored dogs as long as the breeding didn't double up on the white factoring.
All thing being equal, I'd likely chose a darker or traditional pup.

[juliepoudrier]

If you hold this opinion based upon the epidemiological studies, then you should also hold the same opinion about white headed dogs and blue eyed dogs since these phenotypes are also associated with the same health concerns as merle. If you do not hold the same opinion about white head and blue eyed dogs, then you simply have a color bias against merle.

Mark,
How are white heads and blue eyes inherited? I think that makes a difference. If they're recessive or incompletely dominant, then it's possible to get them without choosing for them, so to speak. The same can't be said about merle. (IOW, if you breed a white headed dog to a dark-headed, non-white-factored dog, do you know the likely percentage of white-headed pups that would be produced? Same with blue eyes--it seems they pop up unexpectedly at least some of the time.) Does anyone know?

If I read correctly, the merle gene, even if only one allele, can cause anomalies in the eye structure of the dog carrying the allele. Are you saying the same is true of non-merle dogs with blue eyes? Likewise with deafness. It occurs in dogs without a lot of white on their heads (Joan's Dhu comes to mind) too, so there must be other factors unrelated to color that are also involved.

My point is that while the health concerns may be the same, it seems to me that the genetic causation of those health concerns might NOT be.

J.

[Mark Billadeau]

Julie, you are correct that the inheritance of white headed or blue eyed dogs is not known and would be difficult to use to minimize the correlated health effects (note that I said correlated and not caused because this has not been demonstrated). However, the evidence (while correlated) is inconclusive on the health effects of Mm because most of the epidemiological studies for merle were performed prior to being able to know the genotype of dogs with merle coats. The older studies correlated deafness and eye issues to coat color based upon the assumption that the gene which causes the changes in coat color also controlled the development of hearing and eye development.

In addition not all of the conclusions in the epidemiological hearing studies are still accepted. The Reetz study touted above was refuted based upon the deaf/hearing cutoff criteria applied to the BAER data.

Reetz et al6 reported hearing results for 38 Dachshunds: 8 nonmerles, 19 single merles, and 11 double merles. They reported hearing loss (slight to total, unilateral, or bilateral) in 54.6% of the double merles, and in 36.8% of the single merles (43.3% total merles affected), but in none of the nonmerles. Hearing was tested by determining the BAER threshold to click stimuli under sedation. Any threshold >20 dB was designated as abnormal, not because it is an accepted standard, but apparently because 1 of the nonmerle dogs was determined to have a 20 dB hearing threshold. Only 1 dog, a double-merle male, was totally deaf in both ears (threshold >90 dB) and none of the dogs was totally deaf in only 1 ear. If deafness is defined as the absence of a response to the loudest stimuli presented, true bilateral deafness occurred in 9.1% (1/11) of the double merles and 0% of the single merles, not the 54.6 and 36.8% reported by Reetz et al. The difference in results is explained by the inclusion by Reetz of dogs with partial hearing loss.

The pigment-associated deafness associated with the piebald and merle patterns typically presents as total deafness in 1 or both ears, based on histological studies 11,12 and 1 investigator’s (GMS) experience BAER testing several thousand dogs; thus, the partial hearing losses reported by Reetz seem unlikely to be likely genetic or associated with the merle gene.

Since congenital hearing loss is not partial but is full hearing loss, the criteria used by Reetz is inappropriate for associating coat color to this form of hearing loss.

So now we're back to where we started. Despite the more recent studies (using genotyping) which refute the link between Mm and health issues people continue to make breeding decisions based upon coat color.

[Pam Wolf]

It could be possible that such decisions are colour based, but in working Border Collies it should be based on working traits. While I've seen one blue merle I'd call very good, I cannot say I've seen any merles that I could not find another dog, not merle, that would be better.

[Mark Billadeau]

Pam, then why state there is no reason to breed a merle when you're actually saying there is no reason to breed a mediocre working dog (where coat color does not enter the decision)?

[ShoresDog]

If you hold this opinion based upon the epidemiological studies, then you should also hold the same opinion about white headed dogs and blue eyed dogs since these phenotypes are also associated with the same health concerns as merle. If you do not hold the same opinion about white head and blue eyed dogs, then you simply have a color bias against merle.

Not necessarily. I have a bias against traits that inevitably lead to compromised dogs being born, without any corresponding benefit. I don't think that is true for white-headed dogs, as there are certainly wonderful examples of good working dogs with lots of white on their heads, and as Julie said, the inheritance is likely not the same.

Mark, do you know of any good reason that the merle trait should be maintained border collies, in the face of the evident harm it causes?

[Pam Wolf]

Well Mark, there is that too.

[Mark Billadeau]

Not necessarily. I have a bias against traits that inevitably lead to compromised dogs being born, without any corresponding benefit. I don't think that is true for white-headed dogs, as there are certainly wonderful examples of good working dogs with lots of white on their heads.

There is equal evidence/reports in the epidemiological studies on the correlation between deafness & white heads and deafness & merle; but you choose to only focus on the merle.

You keep saying there is evident harm associated with Mm and I keep saying your evidence is suspect.
I guess we will continue to disagree which studies are relevant (older epidemiological via phenotyping or the newer study using genotyping), on the possible health effects of Mm.

[terrecar]

If they're recessive or incompletely dominant, then it's possible to get them without choosing for them, so to speak. The same can't be said about merle.

Actually, this (last sentence) is not entirely accurate. The merle gene is incompletely dominant. Red dogs can be Mm without showing that pattern at all. Usually in that case, the merle pattern is barely visible at birth and fades with time. The point is, you can conceivably have a red dog with the merle factor without having any visible indication that the dog is Mm (a cryptic merle) .

This is important in light of Shores Dog's argument that the danger of breeding merles is that it increases the probability that MM breedings will happen. It can happen inadvertently with the red dogs.

[ShoresDog]

You keep saying there is evident harm associated with Mm and I keep saying your evidence is suspect I guess we will continue to disagree which studies are relevant (older epidemiological via phenotyping or the newer study using genotyping), on the possible health effects of Mm.

Okay, but my viewpoint that merle should be bred away from does NOT depend on Mm dogs being compromised. I think we all agree that MM dogs can be very badly compromised. My strong opinion that merle shouldn't be bred comes from my belief that in any breed where there are a lot of merles, MM dogs will be bred, whether through ignorance, greed, or by accident. When I fostered for the local Aussie rescue (this rescue actually takes all herding breeds), it made me so sad to see how many blind and/or deaf dogs there were who needed homes and how long it took to place them. One completely blind and deaf white dog has been listed for over three years. Why would we expect this not to happen in border collies? It sure happens with Aussies and evidently Lassie collies too.

Are we willing to see large numbers of blind and/or deaf MM border collies? For what? Is a coat color so important?

[terrecar]

The Reetz study touted above was refuted based upon the deaf/hearing cutoff criteria applied to the BAER data.

Hummm. I'm the one who presented the Reetz study as an example of an alternative conclusion regarding the health impact of Mm, but I certainly don't think I 'touted' it. I'm pretty open minded and usually don't 'debate' something unless I have strong views on it, preferring open discussion to posturing. However, if I were a breeder, I would personally hesitate to do a Mm X mm breeding unless there were some overriding benefit. Having said that, I certainly wouldn't condemn a breeder for doing a Mm x mm breeding; at least not on that basis alone.


ETA: It goes without saying that I would condemn a Mm x Mm breeding.

[concrete]

Wasn't Ralph Pulfer's Tweed a merle? He was certainly an excellent dog and was bred.

Kevin

[workindogs]

I believe that Ralph Pulfer's Tweed was heavily ticked.....but not a merle.

[workindogs]

I'm not sure if this is MM sheltie or not....the webpage calls it a "double dilute", but I found it via another page that referred to it as a double merle.

http://www.shadowhil.../boys/oreo.html

Looks like he's sired a lot of Champions.

EDITED: This is the webpage where I found the link....I guess this sheltie breeder bred to this dog: http://www.jusdandy.com/litr06.htm
and again: http://www.jusdandy.com/litr09.htm

[terrecar]

I'm not sure if this is MM sheltie or not....the webpage calls it a "double dilute", but I found it via another page that referred to it as a double merle.

http://www.shadowhil.../boys/oreo.html

Looks like he's sired a lot of Champions.

Yes it is a double merle. If you look at the sire and dam in his pedigree, you can find photos of both of them on that site, and they are both obvious merles. This is just very disturbing to me. How anyone can justify this, I'll never know.

[workindogs]

I wonder if he's deaf and/or blind.

It seems there are a number of pseudonyms for Double Merle...aka White Merle and Double Dilute.

[KnottyClarence]

I'm not sure if this is MM sheltie or not....the webpage calls it a "double dilute", but I found it via another page that referred to it as a double merle.

http://www.shadowhillshelties.com/shelties/boys/oreo.html

Looks like he's sired a lot of Champions.

It says there is absolutely "nothing wrong" with this dog. Does this mean he can see and hear? So MM doesn't always cause deafness and blindness?

Saw an MM Aussie with a dent for one eye, and the other about a third normal size, plus deaf, once. He just stood there and sniffed.

[Pam Wolf]

Looks like he's sired a lot of Champions.

EDITED: This is the webpage where I found the link....I guess this sheltie breeder bred to this dog: http://www.jusdandy.com/litr06.htm
and again: http://www.jusdandy.com/litr09.htm

And that is the same breeder who breeds Border Collies.

The add says he is a double merle.

[geonni banner]

The term "double dilute" comes from the notion that merle is a "dilution" of the tricolor. A merle to merle bred dog that presents as white is then called by some a "double dilute."

I have known two Collies of this kind of breeding - all white, one with blue eyes and one with one blue and one blue & brown. Both dogs were sighted and seemed to have unimpaired hearing. Both had to be kept out of the sun most of the time, as they were prone to sunburn.

Breeding merles together is a crapshoot. And one I don't feel is ever justified. There is simply too much risk.

[workindogs]

I wonder what happened to the other puppies produced by these Merle x Merle breedings.