Why do we have all this DNA and Health testing done on our dogs?
We do two separate types of Health testing on our Chihuahuas. The first one is O.F.A. (Orthopedic Foundation for Animals) sets recommended testing requirements for each breed based on what is the most common health issues. These tests must be done on dogs over 1 year of age. Currently, in Chihuahuas, it is recommended to have a Cardiac Exam done, A 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 mail them in, to make the information public. The information we gain from this is if we have any issues with knees or eyes and it is 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 being it is a more intense examination, and with eyes, the review involves equipment and specialist education that a regular veterinarian would not have.
We have started to test all our dogs with Embark for Breeders DNA test. This test is expensive but tells us a lot about the unknown in breeding.
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 are not registered or labeled with the correct coat colors. In a breed where you have Merle, this is especially true, merle can be hidden and not visible to the breeder, 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 to responsible breeding, we feel this should be the same in Chihuahuas. This test also tells us what recessive colors each dog is carrying so we can make better choices.
Adult size and genetic diversity are a given. Chihuahuas are very diversity breed, unlike many others breeds but if we are breeding for the future of Chihuahuas being healthier than today than keeping the diversity high is very important. That is why we also love that this test tells us each dogs Genetic Inbreeding Ratios. The coefficient of Inbreeding (COI) is a measure of how genetically similar a dog’s parents are. From a genetic point of view, this translates to what percentage of the genome is identical on both it's maternal and paternal strands (also known as homozygosity). We study pedigrees and calculate this for each breeding, but we are relying on the error of human record keeping. This tells us the actual ratio so we can make sure we are not putting the risk of mutations in our puppies higher than they need to be.
Breed Specific DNA genetic testing we are currently doing is as follows:
Congenital Macrothrombocytopenia (TUBB1 Exon 1, Cavalier King Charles Spaniel Variant)
Degenerative Myelopathy (SOD1A)
Neuronal Ceroid Lipofuscinosis (MFSD8)
Progressive Retinal Atrophy (PRA) Cone-rod dystrophy, crd4/cord1 (RPGRIP1)
Progressive Retinal Atrophy (PRA) Progressive rod-cone degeneration (PRCD Exon 1)
Spinocerebellar ataxia with myokymia and/or seizures (KCNJ10)
As scientists learn more about our breed more tests will be available. Embark also tests are dogs for over a 160 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.
Breeding in this manner through our cost is more up front, 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 and producing sick puppies. We do not breed in a fatal disease unknown and have our breeding program crash and have to restart.
We made a personal commitment to make all results good or bad publicity for other breeders and our puppy buyers to see. 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 firmly believe if you base your breeding program on color first and not the health of the dog, it will only do harm to your breeding program and the breed as a whole down the line.
Breeding better for us means breeding Healthier and using science to help us with that.