DNA Testing

by Anne Zelvys (Science articles can be confusing to the average lay person, with this in mind, I have attempted to write a practical guide to the new aussie owner)

Aims and Application of DNA Testing

Science articles can be confusing to the average layperson, with this in mind I have attempted to write a practical guide to the new aussie owner.

Is to reduce the risk of parents passing on health issues. This testing is just as important for the pet puppy owners as well as anyone interested in showing or breeding, as we are talking about the health of all dogs.

Testing is an easy tool that allows breeders to ensure that the stock they are breeding does not pass on known problems, or that any issues that do exist can be easily managed and perhaps reduced in future. This process is easily done by taking a cheek saliva swab and then shipped to one of the licensed laboratories that then conduct the relevant test for the given breed. A certificate is then sent back to clarify results.

Understanding what the test results mean is sometimes confusing for breeders let alone the pet puppy buyers, so we have provided links at the end of this article to the websites to provide further information. When purchasing a pup you can check the Laboratory Website to see what testing is required for your chosen breed and then you know what to ask the breeders for. Official Health Certificates for the parents of your puppy should be available for you to view.

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  • Nova
  • Australianshepherdpups350
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Future Development

Remember that there may be diseases that do not currently have DNA testing. The science community is working to develop DNA testing further so it is always important for breeders to keep abreast of new development.

It is important that as a breeder we should consider our breeding dogs in the big picture. Hence not to completely discount dogs from the gene pool just because they do not have a Clear for all current tests, otherwise we could restrict the gene pool in the future should new tests be found that might determine which lines could carry issues such as epilepsy or diabeties.

Clear by Parentage

Sometimes when visiting breeders they will mention that their breeding stock might be Clear by Parentage – this means that their puppies parents might not have had testing but the grandparents are tested. If this is the case then they should have the Certificates for the grandparents as well as having the profiling done on their own dogs to verify that these dogs are the correct parents. Really it makes more sense for a breeding dog to have their individual testing done. (as of 2015 the cost for DNA recommended testing is approx. $350)

The following DNA tests are currently recommended for Australian Shepherds.

CEA/CH - Collie Eye Anomaly - Choroidal Hypoplasia

This is a Recessive Gene which can affect many different herding dog breeds such as Border Collie, Collie Rough, Aussies and others. If the dog has one copy of the gene is declared as Carrier, If there is two copies then is Affected – if there is no gene then the dog is Clear (some certificates use the term Normal).

Breeding – ideally it would be great to have both parents as Clear however this is a Recessive gene hence requires a copy from each parent to be an issue. So if one parent is Carrier that is okay provided the other parent is Clear then the pups will not be at risk of developing Collie Eye.

HC (sometimes shown as HSF4) - Hereditary Cataract

With the Australian Shepherd the Hereditary Cataract is a Dominant Gene that is the most common cause of blindness in dogs and sadly there is no cure. Dogs affected may not show symptoms of blindness developing until 5-6 years old hence testing prior to any breeding is worthwhile. There are multiple genes that cause cataract but not all of these are Hereditary, some of the breeds predisposed are French Bulldogs and Boston Terriers.

Breeding – Both parents should show Clear. This is the only way to ensure that none of the puppies will be at risk of developing HC. When a gene is a Dominant Gene then even one copy of the HSF4 mutant gene will test as Affected – Dogs that are Affected 1 Copy of the Hereditary Cataract gene are 12 times more likely to develop the Hereditary Cataract at some point in their life.

MDR1 - Ivermectin Sensitivity

Ivermectin is a cattle and sheep wormer and found in many of the products also used to treat dogs. Most breeds of herding dogs can have issues with Ivermectin based drugs, so caution should be taken when using drugs from the list or even if in the vicinity of farms where dogs could eat cow or sheep poo when farmers have treated their stock.

With testing, 1 Copy is shown as CARRIER, if there is 2 copies then dog is AFFECTED. If both parents are Affected then we know the pups will also be Affected hence take care what drugs used, there are alternative drugs that can be used ensure your vet is aware. (Note: some owners of Carriers of MDR1 Sensitivity have reported that they have had dogs react when treated with the listed drugs, hence it may be worth playing caution with ALL Aussies).

Breeding - Many dogs are Carrier’s or Affected and still used in breeding programs as it would limit breeding too the detriment of other health issues by discounting the wider gene pool. Affected dogs can be viewed like any other allergy and there are other alternative drugs that can be used thus not placing the dog at risk. It is just a case of understanding what to avoid.

NBT - Natural Bob Tail

This is a confusing one for many of the general public who are used to seeing a dog with a tail. However there are a few breeds where individuals that carry the NBT gene will cause a shortened tail or even an absence of tail. There are no other health issues for the dog that are related to this trait. Some other breeds seen are Rottweiler, Welsh Corgi, Old English Sheepdog.

In the USA a very large percentage of Aussies are docked short at birth regardless of the tail length the pup is born with. However under Australian Standards it is accepted Aussies could have any length tail – docking or shortening the tail is against regulations here unless by a veterinary for health issues. However what you will likely see in the show ring is nearly 100% full bob tails.

The NBT gene is a Dominant trait hence only a single copy is required in order for a dog to have the shortened tail. So if results show CLEAR then the dog will have a FULL tail. If results show as CARRIER (which actually means that the dog is Affected) hence the dog will be NBT this means the pup may have anything less than full tail. The length of the NBT tail is determined by other genes that are currently not known.

Breeding – So with breeding Clear to a Clear – ALL puppies will have full tails. If breeding a Clear to a Carrier, pups are approx 50% Full Tails and 50% shortened tails. If breeding a Carrier to a Carrier, Pups are approx. 25% Full Tails, 50% shortened tails the remaining 25% pups that receive 2 copies (AFFECTED) of the NBT gene will not survive: they will either be reabsorbed during pregnancy; born dead or die within a very short time. (note percentages will vary from litter to litter but will balance out over all breeding eventually).

Alfoxton Breeding Note: Breeding NBT sire to NBT dam is therefore likely to produce smaller numbers of surviving pups, hence if 8 embryos at 4 weeks into the pregnancy could reduce to 6 pups by whelping of which statistically there could be 2 full tailed pups and 4 pups with shortened tailed. In our breeding experience approx 10-20% of NBT pups are expected to be Bob Tail the rest have had various lengths from ¼ to ¾.

Breeders seem unaware of this fact and as we do not have compulsory DNA regulations to know the true NBT status of breeding stock bred either here in Australia or from USA, so this makes collecting statistic for a better picture very limiting.

Official Status of DNA Testing

There is no official requirement for breeders to DNA test their breeding stock, however most ethical breeders make the effort to reduce risk. It is also worth noting that these test results are not added to the Official Registration Certificate of the parents issued by the governing associations. This is such a shame, as the health records should be given equal or even more importance than any show records. Perhaps in the future this will change.

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