In last week’s article, I discussed the tremendous amount of data that is now available. Yet, even though there is more information “out there” than ever before, breeding dogs has become more difficult, not easier. In this week’s article, I am going to go over strategies that breeders can use on an individual basis to cope with test results as they come in from various sources. Did I say “cope with”? Yes, I did! Read on…
In the beginning, dog breeding was as much (if not moreso) art as science. Breeders studied pedigrees, learned the prominant lines (male) and families (female) in their breeds, and which “nicked” well with each other. People did not utter words like “gene pool”, “diversity”, or “gene frequency”. While the basics of inheritance were well understood by many, it was their sense of where the good genes could be found and how to mine this knowledge which separated the great breeders from the rest.
Breeders today have to work with a great deal of information in order to come up with a breeding that they hope will contribute quality pups to the next generation. There is so much information, in fact, coming from so many diverse sources, that breeders are at risk of becoming technicians, simply breeding for a “good” test result, rather than artists looking at creating the equivalent of the next canine masterpiece. I call it the difference between negative breeding (breeding to get away from some percieved unwanted trait) and positive breeding (establishing a vision and breeding in a positive direction toward that goal).
It’s important to maintain balance in breeding decisions. Tests should not be disproportionate in the decision-making process. Tests can become the sole driving force in a breeding program; conversely, some breeders do not test at all! Neither one is conducive to producing quality animals.
Breeders need to not only have a working understanding of the diseases they are testing for, but also need to know how those diseases affect the breed as a whole (macro-scale), as well as on an individual level (micro-scale). Breeders deal with both: on the macro-scale side of things, not wanting to pass on deleterious genes to the next generation, while at the same time not damaging a breed’s diversity. On the micro-scale side, breeders need to know how to counsel puppy buyers who end up with a pup who does not get a passing test result. They also need to be able to sell pups, and promote their stud dogs! Inability to balance macro- and micro-scale effects of genetic tests creates problems in one direction or another. Too much emphasis on micro-scale, and other genetic issues for which there is no test can magnify in a breeding program. Bottlenecking and diversity can be lost if too many breeders follow the same “recipe” for breeding. Too much emphasis on the macro-scale can cause a breeder to have difficulty selling pups, or a stud dog goes unused becuse of popular perception of that breeder as a “maverick”.
So, how does a breeder or individual dog owner cope when the test results start rolling in? How to keep it all in perspective when that phone call comes in that a pup is dysplastic, has cataracts, has an unexplainable test result? This is where a breeder’s knowledge, and a breed-centered Parent Club or Breed Association can be most valuable. Every scenario is a bit different, as each type of test has a bit different approach. I am grouping these into logical (for me) groupings, rather than disease-by-disease, which would be a very long article indeed!
Polygenic diseases with no gene test: these are genetic issues that do not yet have any gene-based test for them. Instead, we do what is called a phenotype test: assessing a dog for evidence of the results of deleterious genes, rather than looking at the genes themselves. Screening tests in this category include OFA/PennHip/OVC for hips, elbows, patellas, thyroid, cardiac, shoulder OCD, and CERF screening for cataracts and entropion. Some of these tests are the oldest and most commonly used, yet the diseases they screen for are extremely complex and involve several to many genes.
My mantra for all test types is: get a second opinion! In some cases, and depending on breed (this is where info from your Breed Club would come in handy!), waiting a while before retesting could be useful. Since these tests are done by visually examining a dog or its x-rays or other imaging, human error becomes a factor. Differences in positioning, radiograpic density, and sedation all play a role in how an x-ray can turn out. Also, knowing your breed’s developmental quirks factors in. For instance, unlike the majority of breeds OFA reports on, Chessie hips can improve marginally to markably between the ages of two and four years. Waiting six months to a year and redoing films can yield vastly different results. Lastly, it’s always useful to send the films in to OFA. While your vet may be a great guy (or gal!), the OFA screens many more hips than the average vet, so while your vet may deem the x-rays as not able to pass, OFA may have a different idea on the subject.
Likewise, visually examining a dog’s eyes for evidence of hereditary diseases is fraught with error. The lighting in the exam room may not be right. The vet doing the exams may not be used to looking at your breed’s eyes. The eyes of all mammalian species actually start out as part of the skin; in some breeds (like Chessies) which have unique coat types and coloration, odd “artifacts” can remain from the embryonic development stages which can mimic a cataract. If a dog or pup is diagnosed with cataracts, waiting six months to a year and redoing the exam is the best advice. If you are relatively new to the breed, or this is your first encounter with a non-passing result, consult with other knowledgeable breeders for the name(s) of Veterinary Ophthalmologists in your region who have experience examining many Chessies.
As a breeder, when you get that phone call from a puppy buyer, don’t feel shy about asking those probing questions. These can be difficult calls to field; emotions can run high, the puppy buyer may feel used, etc. It’s a good idea to remain calm, not be accusatory, and find out the details. It could save the dog/pup in question, and salvage the breeder/buyer relationship. There are vets out there who recite the mantra that all breeders are bad and just in it for the money. If your puppy buyer has the misfortune to have one of these vets, your work is cut out for you! Have factual references you can point your puppy buyer to, like articles on the OFA website, or your breed’s Parent Club.
Single-Gene DNA-Based Tests: These are DNA-based, true “genetic” tests which look at disorders which are caused by one gene, rather than several genes acting together. In Chessies, these diseases include prcd-PRA, EIC, ED/SF and MPS-VI. “OK smarty-pants” I hear you say, “how does a second opinion apply HERE?” Here’s how.
All DNA-based tests rely on sampling the pup or dog in question. They also rely on laboratory testing of those samples, and accurately documenting and recording those results. There is room for error at both ends of this process.
When sampling for DNA, a blood draw is always the gold standard. Cheek swabs are efective, but it’s too easy to get samples mixed, especially where litters of pups are concerned. Puppies swap spit all the time! Add in the fact that in many cases, owners take their own samples, and the chances for error multiply. In any case where a test result is from a litter of pups sent in by the breeder, it is prudent to have the test redone via blood draw (if possible) or have your vet do the cheek swab following the mouth cleaning protocol to the letter. Yes, retesting DNA is expensive, but not as expensive as spaying/neutering an otherwise perfectly good dog.
At the other end of the process is the laboratory doing the testing. Yes, there are many labs out there offering testing, sometimes at a greatly reduced rate. There is nothing wrong with seeking some overhead reduction, but just be aware that some labs are using earlier or incomplete versions of the tests available. Results may not be accurate, and you may have to suffer the embarrassment of explaining how a pup could test “affected” when both parents tested “clear”. To be on the safe side, I recommend that the DNA Labs listed on OFA’s site be used. This will save you the expense of retesting at a later date if/when inconsistent results crop up.
Next week, I will tackle DNA Tests for Polygenic Traits, a unique (and still fairly new) category of testing, that is causing headaches and waves of anxiety throughout the dog-breeding community. Not to mention, posing a real threat to purebred dog breeding, worldwide!