Sunday, December 4, 2011

Mismark Case Study: Australian Shepherds

According to the AKC, the Australian shepherd comes in four "acceptable" colors, seen above: black, red merle, blue merle, and red. All of these colors may come with or without white markings and/or tan points (often termed "copper"). Image is from Wikimedia Commons under a Creative Commons license.
This Aussie has no tan points.
Australian shepherds, or "Aussies" as they are often called, have become popular dog of choice, especially for those who participate in many of the popular dog sports. A very American breed, despite what the name implies, Aussies are a common sight at events such as flyball, agility, and disc dog. Though the are often described as coming in "four standard colors," the standard actually allows for sixteen different color and marking combinations (black and liver with or without merle, Irish white, or tan point). However, there are also a number of colors or marking patterns that are not allowed under the standard. These are as follows:

This Aussie has too much facial white
  • "Incorrect" white markings
    • May include piebald or excessive white on the face
  • Sable
    • With or without merle or white markings
  • Yellow (recessive red)
    • With or without white markings, may hide merle
  • Brindle
    • With or without merle or white markings
    • May be in combination with the tan point gene
  • Double merle
    • Not allowed by standard mostly due to excessive white
  • Dilute
    • May be in combination with any of the previous colors

Too much white makes this Aussie a mismark
All of the above colors appear in the breed with relative frequency, some more so than others.  Many are inherited recessively (yellow, dilute, excessive white), so as such it's nearly impossible to completely breed out the color. In fact, it has been proven nearly impossibly to completely eliminate the modifiers that cause excessive facial white from the population. Yellow, piebald, and excessive facial white are seen far more frequently than is dilute (which turns black dogs blue and liver dogs fawn). Piebald's most noticeable feature is when white starts crossing the line between the withers and tail, and sometimes it's a tough call as to whether a dog is piebald or not. Interestingly enough, in the show world there has been selection for a lot of white on dogs, so that makes it even harder to determine if a dog is piebald or not.

This Aussie is a sable mismark
Other colors are only recessive to certain colors, so they will only show up in certain lines (sable and brindle are both recessive to dominant black, which is what causes the dogs without tan points). One way to select against the appearance of dogs who are sable or brindle is to select for tan points. By breeding only tan pointed dogs, sable is effectively eliminated. Also, since solid black hides brindle, having a dog with some red makes it easier to identify those that do have brindle.

This double merle Aussie is a deaf mismark
In addition, despite the fact that the standard allows for dogs without tan points or white markings, you will rarely see dogs in the show ring with any of those phenotypes. If you do find them, they're usually only seen coming from the lines bred for working or sporting. In fact, this is also true of merle, where most of the dogs seen winning in shows are merle. Since the color is so popular in the show community, this has the potential to narrow the breeding population to only merles as breeders try to produce more show-quality, flashy merle dogs. However, this leads to the potential to produce, you guessed it: double merles. Double merles have a very high chance of being blind and/or deaf. Breeding of double merles should be avoided at all cost, especially by breeders who claim to care for the health of their dogs.

This Aussie? would be a yellow mismark
As with every breed standard, I see a lot of problems with the standard for the Australian shepherd, but I also see problems with the dog show community. Though the standard allows for sixteen different combinations of color and pattern, only four are really ever seen in the ring. On top of those, only two of those four colors are favored by judges. Worst of all, those two colors can lead to serious health problems when bred together. By making use of diversity, not only can double merles be avoided, but overall breed health may be improved. The breed has been split into two subsets: show and working/sporting. Though these are not color classes, it is still a narrowing of genetic diversity that should be unnecessary. In addition, to some extent it is almost like breeding for color classes. This is due to the heavy preference for certain colors in the show lines while little to no preference is seen in the working/sporting lines. More narrowing of the breed has come from the breeding of the miniature (an now toy) Aussies, which have been selectively bred for their smaller size.

2 comments:

  1. There suggested favortism in the breed ring towards merles is inaccurate. There is an even mix of champions of both red and black, merles and non-merles.


    There still remains a bias among judges and owners for very prominent white markings and the show lines have seen an influx of piebald white genes to encourage the maximum amount of trim.

    It is something that the long time breeders and judges from the parent registry discourage, but a lack of mentorship in all breeds, the Australian Shepherd included, means that novice owners and breeders produce what they like to see in phenotype and ignore genotype.

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