International Dog Health Meeting #4 (Oceana Region) - Theme: Breeding for Health and Purpose - Post Meeting Resources

Click here to view pre-meeting resources for an overview of the workshop, speaker bios, and more.

Full Video of the Meeting:

Note: Only those who attended the webinar “live” are eligible for the product giveaways and $10 Orivet Loyalty Points offer. Deadline for product giveaway submissions is 10 August, 2023. Attendees will be contacted via email with details on how to claim their Loyalty Points.
 

Summary of Questions and Answers:

More Q&As may be added, and you can still email us with your questions...

Questions Answered During Meeting:
 

Question: Epigenetics, does that mean that ensuring non-stress environments for our dogs, over successive generations, can create a better temperament over time?

Answer: In the meeting, we discussed the impact of environment and health. Genetic inheritance is known to be a significant contribution to temperament, but the environmental factors in utero, epigenetics, etc. can impact how the genes are expressed... and of course there are additional environmental effects after the dog is born! Myrna's talk goes into a bit more conversation about this. 

Question: My female dog has 1 gene of a variant and the male dog is clear.  Her first litter produced all clear pups.  Will this be the case most of the time, or will there be pups that will have her gene and only carry the 1 gene?

Answer: In the meeting, we talked about how the chances are very small to have an all-clear tested litter, but this is not impossible. See further questions below. 

Question: With a specific genetic condition called Scottie Cramp in Scottish Terriers, there is currently no DNA test to show mutation. If a dog/bitch is a known carrier based on having produced affected dogs by being bred to another suspected carrier, should all future suspected carriers be removed from a breeding program given the aforementioned lack of testability? 

Answer: In the meeting, we provided an answer, but felt an expansion on this discussion would be useful... Any dogs clinically affected by the disease should be removed from breeding. As all available research suggests the disease is inherited in an autosomal recessive form, dogs who are likely carriers should not be bred to other dogs who are likely carriers.

Breeding dogs who are likely carriers to those who are confidently clear could be reasonable to avoid perpetuating risk of the disease and also avoid constricting the genetic diversity in the breed. It comes down to how much risk a breeder feels is reasonable, and if the mating has other benefits that justify the risk. Determining those dogs who are clear can be challenging, and should be based on multiple mating results and pedigree analysis.

One of the many challenges with this condition is that there appears to be a lot of variation in severity, which could indicate that even if a causal variant is identified, there are likely other genetic factors at play. As most dogs show some signs before the age of 1, it should be possible to reduce risks of accidentally using an affected dog, at least. This condition also has very similar signs to cerebellar abiotrophy in the breed (and many terrier breeds), so there is also a challenge in ensuring a correct diagnosis. 

Additional Questions Received:

Question: Do you mean that carrier isn't always passed to the children?

Answer: When you breed a carrier and clear tested dog together, each puppy (not divided across the total litter) has a 50% chance of being either clear or carrier. In most litters, some puppies will be clear and some carrier – but you could have a whole litter of clear puppies (or a whole litter of carrier). This is why testing the puppies is important – you cannot assume which are clear or carrier.

Question: So, can you categorically guarantee that a 'carrier' dog of PRA, will never express the genetic fault and exhibit PRA that it 'carries' ?

Answer: In an autosomal recessive (AR) simple mutation disease where a specific variant has been identified and is causal for the disease, dogs who carry only 1 copy of the variant (mutation) will not develop that specific form of the disease. This happens because for simple AR diseases, having 1 normal copy of the variant is sufficient to have normal functionality. 

In Progressive Retinal Atrophy (PRA), however, we know that many breeds have multiple different types of PRA that have been identified, so the test for one type of PRA does not determine risk across all known types of PRA (or of course, any unknown forms). This is where a panel or group of PRA tests may be helpful, as you could receive results across multiple forms of PRA. 
It is also possible for some AR tests to have “incomplete penetrance” or have other forms of inheritance. For incomplete penetrance, there is an additional unknown risk associated with the manifestation of the disease – e.g., some dogs have 2 copies of the mutation (genetically affected) but do not get the disease. 

Question: I'm very well aware of genetics and have bred for litters with very low COI. However, in my breeding program of over 30 yrs, those very low COI litters have resulted to the worst litters in health-wise. Even if both parents have lived healthy lives. Could it be that those lines have had different switch-off genes, which are lost in combining them? I'm lost with this issue.

Answer: It would be helpful to answer this if we had more information on what you mean by health. Breeding for genetic diversity essentially introduces more variation within the breeding stock. So, if by health you mean that conformation or temperament is more variable, or different than what you expected, or less predictable, that could be due to the introduction of more genetic variety in your plans. You could be experiencing some impact of masking genes or other unknown factors, but most likely the increased variation is causing unexpected or undesirable results. It can be a big challenge to breed for type without resorting to breeding for relatedness, as relatedness and inbreeding is like a "short cut" to desirable traits... but potentially with undesirable risks such as breed-specific inherited diseases. 

If you’re trying to make changes within your individual plans, I try to think about selection in a hierarchy: 

1. Are the dam and sire clear of signs of any (inherited or not) disease? How are their near relatives: parents/siblings/off-spring?
2. Do the dam and sire have a good temperament that reflects my preferences and compatible with the breed standard?
3. Do the dam and sire both have conformations that meet the breed standard, or are improvements working towards the breed standard from my last mating? Is the conformation supporting fitness and function? (e.g. no breathing, hip, elbow, coat, eye, etc. problems or extremes)
4. Are the genetic test results complimentary? E.g., for known inherited disease can the risk be reduced or eliminated?
5. Are the clinical/physical test results complimentary? E.g., for known complex inherited diseases, can risk be reduced?
6. Finally, if all other things are equal in choosing between sires (or dams?), is there a choice that will help maintain or improve genetic diversity? 

In summary:

• What can I observe in the dog? (Phenotype)
• What can I test for? (Genotype)
• What can I do for the future? (Genetic Diversity)

Ideally, genetic diversity management should be strategized and supported at a breed-wide level - such as steps to manage popular sires - increasing positive changes across the breed as a whole. 

Question: I wonder does Epigenetics have anything to do with the CRISPR-Cas 9 gene, also?

Answer: Epigenetics is the study of how environmental or other factors external to the genes themselves can cause changes in how the genes work. CRISPR and other gene editing technologies are looking at how to modify or change the genes themselves. It’s all in a similar universe of genetics, but they have different purposes. Epigenetic changes are, in theory, reversible as the DNA is not changed. CRISPR gene editing changes the DNA. 

Question: Myrna says that 'breeding is an art' so if this is the case, is she saying that it isn't a 'science' - so what part does genetics, DNA tests, etc. play?

Answer: I think Myrna's talk indicates that she fully sees the value in using science to support the "art" of dog breeding. Genetics, DNA tests, and other resources could be considered the tools of the artist!  Balance in all things...

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