Why all the Health Testing? Don't you know your lines?
In the decades I have been breeding canines, if i had a penny for every time i heard another breeder say " I know my lines," I would be a millionaire. Can you know your lines? I am not a wizard who can look at a dog and see recessive genes. The fact is that breeders who say this don't have this superpower either. They are guessing. Instead of guessing what a gene might have been hidden for decades in my lines, we use modern science to "see and know our lines."
We do two separate types of Health testing on our Chihuahuas. The first one is O.F.A. (Orthopedic Foundation for Animals), www.offa.org, which sets recommended testing requirements for each breed based on the most common health issues.
These tests must be done by a veterinarian that is O.F.A. certified (examples below in photos of OFA certificates and CHIC ) and on dogs over one year of age. If a breeder is selling a dog or puppies from parents they claim are OFA tested, please ask to see these documents, or you can search the dog's names on the OFA website linked above to ensure they are being truthful.
Currently, in Chihuahuas, it is recommended to have a Cardiac Exam done; preferred is an advanced Cardiac with Echo, manipulation of the patellas (back knees) and grade them for Luxation, and finally, an annual exam by a board-certified veterinarian ophthalmologist all Veterinarians signs a certification form on the results. We take these results and send them to OFA (with money, of course) to make the information public and send back Certificates as proof. The knowledge we gain from this is if we have any issues with knees or eyes that are minor, we can make sure we do not breed this dog to another dog with similar problems—making breeding choices based on health first.
It has been our experience that during a routine vet visit, health issues did not show up that did on the O.F.A. exam. The reason is it is a more intense examination, and with eyes, the review involves equipment and specialist education that a regular veterinarian would not have. Eyes must be dilated for the exam.
We have tested all our dogs with Embark for Breeders DNA test. This test tells us a lot about the unknown in breeding regarding recessive genes. We are over five generations into using Embark. Many breeders tell us they do not have to use Embark because “They know their lines,” but I question whether they are “wizards” and can see recessive genes. I know I am unable to do this magic.
Many companies do tests for Health, Ancestry, Inbreeding Co-efficiency (much more accurate than pedigree), and Coat Color on the market. We prefer Embark due to the updated tests they add without charge, the breeder tool for planning mating, and continual education and webinars to educate breeders and pet owners.
Embark identifies breed-specific genetic disease risks and traits like coat and color with a simple cheek swab. Coat Color testing is essential as many Chihuahuas need to be registered or labeled with the correct coat colors. In a breed where you have Merle, this is especially true; merle can be “hidden,” “cryptic,” or not visible to the owner, but if bred wrong can lead to many health issues like blindness and deafness. In horses and many other breeds' coat color, testing is routine for responsible breeding; we feel this should be the same in Chihuahuas. This test also tells us what recessive colors each dog carries so we can make better choices.
http://www.doggenetics.co.uk/merle.html offers unique insight into coat colors, esp. Merle. We also have a Merle Blog on this website just in Chihuahuas.
Adult size is guessed, and this is becoming more accurate with time and our understanding of how this gene works within our breed. Genetic diversity is a given, which is essential for any breeder to know. Chihuahuas are a very diverse breed, unlike many other breeds. However, if we are breeding for the future of Chihuahuas being healthier than today, keeping diversity high is especially important. That is why we also love that this test tells each dog's Genetic Inbreeding Ratios. The coefficient of Inbreeding (COI) measures how genetically similar a dog’s parents are (In humans, we understand that children produced from close relatives have more health issues, the same applies to dogs). From a genetic point of view, this translates to the percentage of the genome identical on both its maternal and paternal strands (also known as homozygosity). Years ago, before DNA, we studied pedigrees and calculated this for each breeding, but we are relying on the error of human record keeping. This tells us the ratio of duplicate genes to ensure we are not putting the risk of mutations in our puppies higher than they need to be.
These issues are known, and are Chihuahua-specific DNA genetic testing we are currently doing is as follows:
Progressive Retinal Atrophy, PRCD Exon 1
Progressive Retinal Atrophy, crd4/cord1
Neuronal Ceroid Lipofuscinosis 7, NCL 7
Spinocerebellar Ataxia with Myokymia and/or Seizures
Intervertebral Disc Disease (Type I)
Chondrodystrophy and Intervertebral Disc Disease, CDDY/IVDD, Type I IVDD
Degenerative Myelopathy (SOD1A)
Example of Embark Results
As scientists learn more about our breed, more tests will be available. Embark also tests dogs for over 218 other diseases. This report tells us if our dog carries only one mutation or two (we could not know this without genetic testing). This information we share with our veterinarians, and then we can make sound choices on who should keep in our breeding program, who cannot be bred together (i.e., Both carry one copy of the same mutation), and who is free of all known diseases. We believe in transparency and honesty, so all results are PUBLIC, and we publish the links on our website for anyone to read.
Breeding in this manner through our cost is more upfront; over the long haul, it saves money, time, and lives. We do not invest in unhealthy breeding dogs for years only to find out they produce sick puppies. We do not unknowingly breed in a fatal disease and have our breeding program crash and must restart.
We are committed to making all results good or bad publicity for other breeders and our puppy buyers. Without honesty, our breed will not overcome some of the more common issues that plague this breed.
Since all colors are acceptable in Chihuahuas, we do not breed for color; we passionately believe if you base your breeding program on color first and not the dog's health, it will only harm your breeding program and the breed down the line.
Breeding better for us means breeding Healthier and using science to help us.