S'Dandi Shih Tzu
All Rights Reserved
2000 - 2008
Sally and Dick Watkeys
8235 Outer Drive South
Traverse City, MI 49684
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S'Dandi Shih Tzu
Just BePaws . . .
VetGet testing. Is that anything like the “Black Plague?” At times it seems that way. If you comment to some people that you are testing, the response usually is: and…well, what happened? Of course, if you relate the results, and they are not perfect, there is the possibility of annihilating your breeding/showing program in the Shih Tzu world. So many people do not understand how to use this test as a tool instead of as a suicide pack for those unfortunate animals that carry one or both of the dreaded “markers.”
I was one of those people who didn’t understand all the implications of the test several months ago. Many questions surfaced in my mind after attending the VetGen seminar given at the 1999 National. In the first place, it involves a huge sum of money. It also involves putting your kennel’s future in the hands of someone unknown with that “human error thing.” You talk to other breeders. Lots of them aren’t going to test “until the test is more definitive.” Then, there are those who test one or two animals, decide that if the dog is from a breeding other than theirs, it must be the fault of that dog because they’ve never had any problems. Next are those who jump on the bandwagon, test, and discard the dog if it carries even one marker with no thought whether it is an outstanding example of the breed or not. This alone could wipe out the best dogs of any small kennel situation not to mention possibly some of the best dogs of our breed. Last, are the people who test, look carefully at the results, the animal involved, and move forward with the knowledge that they now have another tool to use in their breeding program, a tool which will aid in the decisions to produce the best possible Shih Tzu.
Testing is a very scary process in the best of circumstances. Once the decision to test has been made, there is the anticipation during the time it takes to receive the kits, then, actually administer those three swabs, mail them off with a prayer (I usually add a kiss for good luck,) and wait for the results. Lots of thoughts surface during those long two weeks. How will the results come back? How will this affect my breeding program and me?
With me, it was devastating at first. The first three tests came back M/N. I panicked! Now, what? Place all those animals? Slow down. Think, think, and think some more. Where can I go for advice?
John Duffendack of VetGen was most helpful. He calmed my fears, talked to me about my animals and answered my many questions. My friend, Joi Rush, was the next call. She added support to my wavering confidence. We talked about the big picture and how to handle the results carefully.
Besides the VetGen test, before breeding, each dog should also have a complete blood workup with all the other tests run to compare with the RD result. These should include a Thyroid check, Creatinine, Bun and Urine Specific Gravity. If any of these results are questionable, and the RD result makes you wonder if you should breed this animal, you probably shouldn’t. Here, several considerations have been investigated, not just one test. It must be remembered that the 20-30% margin of error is definitely a large figure. If you test 10 dogs, 2-3 could have the wrong results. That is why there is a need to have other test results to consider before discarding the marker dog from a breeding program, especially if said dog is a wonderful example of the breed. We can’t afford to eliminate those good animals from our already small gene pool. We all started with the same, original 14 dogs from the palace.
To clarify the terminology, M means the dog is carrying one marker of the disease, N means the dog is carrying no markers or clear. M/M means the dog is carrying both markers, one from each parent, while M/N means the dog is carrying only one marker with the other being clear.
From all the research I’ve done since getting involved with RD testing and talking to others who are also testing, most of us are looking at about 90% of our breed carrying at least one marker leaving only about 10% clear. That’s rather scary!! In questioning seven breeders living in that many different parts of the country who have recently tested their stock, the percentages were much higher. The numbers were astounding. Total tested: 65 dogs. Total tested M/M: 30. Total tested M/N: 31. Total tested N/N: 4. That makes just over 6% of this test group clear with approximately 94 % carrying at least one marker. Incredible! Also, look at the number of M/M results. Isn’t that frightening?!! OK, what now!!!!
What should be done about breeding? After all the test results have been gathered and evaluated, look carefully at the dog. The more selective we are with our breeding stock, the better are our chances of producing healthy puppies that will compliment our breed. After this evaluation process, which dogs do you put together? Pedigrees are important, of course, but now, it’s complicated by VetGen’s results. Once you have them, they’re always in the back of your mind. I don’t know about you, but, for me, the result becomes part of the dog. A little knowledge of genetics is necessary to proceed.
Breeding two M/M dogs will produce all M/M puppies. Is that what we want? This is really scary to me. The puppies will be 4 times M/M. Doesn’t that mean we’re multiplying the chances for RD in the puppies? I think so.
Breeding a M/M to a M/N will produce some M/M puppies and some M/N puppies. Do you take the chance? How wonderful are the two being used for breeding. Are you willing to test the litter to see which one will be kept for future breeding?
Breeding a M/M to a N/N will produce all M/N puppies. Keeping your goals in mind, this is a workable situation. Take the M/N puppy and move forward.
Breeding a M/N to a M/N will produce a M/M, 2 M/N, and 1 N/N if the genes fall the way they’re supposed to. What about puppy #5 or #6 if you’re so lucky to have a large litter? This is where you take your chances. You may get another N/N and yet, you may get another M/M or more M/N puppies.
To maintain a large enough pool of good breeding stock, it may be necessary to consider breeding a N/N dog to a M/N or a M/M dog. Of course, the best scenario is to breed two outstanding examples of the breed, both N/N and get all N/N puppies. That is supposed to be what happens. Not always! Again, this is where that margin of error comes in. I know of a breeding between a N/N stud and a M/N bitch, and the offspring tested M/M. That was a surprise for everyone involved and a big disappointment for the breeder as the M/M puppy was the one she had decided to keep. Now, which test is accurate-the tests on the breeding pair or the test on the puppy? No one can be sure. This is why it is so extremely frustrating at this particular time with only one marker being identified. Looking for the other marker, the gene involved, the mode of inheritance (which has not yet been determined) is like looking for that proverbial needle in the haystack.
Without taking a genetics course, this is the way I’ve come to understand it all.
Each dog is made up of 39 pairs of chromosomes-one set from each parent. “As the maternal and paternal chromosomes line up, they can and do exchange segments, so that at the time they actually separate, each of the two chromosomes will most likely contain material from both parents. These chromosomes are flexible. They bend and twist around each other. They are also self-healing. When both break, they may heal onto the paired chromosome. These breaks are called crossing over.” Basic Genetics II.
The crossover of the chromosomes can cause a false positive result. That’s where most of the problem is. A chromosome can act as if it’s affected by the marker even though it isn’t due to the crossing over characteristic that occurred in the recombination. “If a crossover occurs between the genetic marker and the defective gene, recombination occurs, meaning the marker might suggest there is a defective gene although the defective gene may no longer be present.” Today’s Breeder.
Very confusing? You bet!!! Hard to understand for the layperson? Absolutely!! However, in order to do the best breeding, it is necessary now to begin to study and understand all the parameters. We are no longer just putting together good pedigrees. We are striving for the continued health of our breed.
While it is important to reduce the frequency of this marker in our breed, it is also imperative not to remove much more than 10% of the unwanted gene in a single generation due to the dangerous effects on the overall genetic diversity of the breed. A better understanding of this concept is available by reading the article, “Population Genetics II: Reducing High Gene Frequencies” on the Internet Bowlingsite listed at the end of this article. “For the best benefit of the breed as a whole, the avoidance of carrier to carrier matings should be accompanied by some selection against carriers, but not by actual elimination to the carriers from the gene pool when such elimination would lead to too rapid a restriction of the gene pool.” Population Genetics, pg.2. As I see it, this is where our breeders need to be extremely careful. We can’t afford to lose the outstanding animals in our breed. Looking at the statistics listed in the beginning of this article, we must proceed with great caution. Careful selection is a must.
In my continued quest for additional information, I put everything I have gathered into a folder and took it to my vet. He was very interested in the articles from the ASTC and VetGen along with some information from the Internet and various emails with discussion and facts that I had come across. His input was that within a few years we will have moved forward to that step where all the research is in place and a definitive test will be available. Hopefully, it won’t be too late to save our breed from this terrible disease. Hopefully, we may still have a few animals that test M/N or N/N. In the meantime, it behooves all of us to test, in some way, the animals we plan to use for breeding. Breed only the best. Use all the tools available to help you accomplish your goals. Just remember, even M/M is workable if you like the dog, breed it carefully and have a plan for the future. And… according to John Duffendack of VetGen, just because the dog has one or two markers does not mean that it will ever be sick or produce sick puppies. The possibility is there, not the probability.
There are pros and cons to VetGen testing. Making the decision to test is a big step. It shouldn’t be entered into lightly. However, it’s all we have at this particular point in time. Work carefully, slowly, always with realistic goals in mind. I’m striving for all clear breeding stock at our house within five years. Working diligently, I hope to accomplish that goal.
The last consideration is for all of us to work together. Let’s not let this RD test be a plague. There is no need to point fingers at any one breeder. All of us are in the same boat. We’ll sink without each other. We need to cooperate across the country, put together the best dogs and help each other. We need to strive to produce those N/N puppies and promote the health of our breed.
Below are some resources I found very helpful in trying to understand genetics, testing and all the components necessary to move forward for the benefit of our breed. I would also be most happy to discuss or help anyone who would like to contact me personally. My email is email@example.com. Good luck and healthy breeding!!!
Today’s Breeder, issue 32, Genetic Gamble pg. 8-10
Unraveling Clues pg. 15-17
AKC Gazette, Aug.1996, Genetic Markers pg. 54-57
Genetics of the Dog, Willis, Malcolm
Population Genetics II
Reducing High Gene Frequencies
Basic Genetics III
Basic Genetics I
Basic Genetics II