LONG LIFE

Dale Malony: What you’re saying about how a gene may be suppressive reminded me of how a lot of people sometimes set their goals to avoid doing something wrong - we select our dogs to avoid certain diseases only… Nobody’s selecting for long life or spotting the dogs that these dogs just never have a health problem. Have you heard of anybody who has done any kind of experimentation to try to study animals that are particularly immune?

Dr. Padgett: Well, you sort of do that if you select for long lives, you select against all aborations at once. That’s really what you’re doing. And, we know long lives…long livingness is genetic. It’s clear that there are healthier people groups than other sets of people. Of course, if they’re healthier, then you’ve ruled out everything that would kill them all at once.

I don’t know of anyone in dogs…I’ve talked to a lot of breeders, especially the giant breeds like the Bernese Mountain Dogs, and they’re always complaining to me that their dogs are dying out at 6 ½ and 7 years. We know they can live longer than that because we’ve got Bernese Mountain Dogs that live 15 years. I ask them "do you breed for long livingness?"

Others’ Questions: So if you know that his dad and grandpa have lived until 18 then…

Dr. Padgett: Absolutely. That you can do. You can select for long lives. You do it by looking at the parents of that dog.

Line Breeding
Debbie Martin Question: This is from Joanne and she’s on a live doggy discussion group for all kinds of breeds. …There are many people that preach doom and gloom if one inbreeds or line breeds. So, what do you preach? Do you think that genetic depression will kill the breed?

Dr. Padgett: I don’t believe that.

Joanne Chanyi: I don’t either.

Dr. Padgett: No matter what anybody tells you, ask them for evidence of what’s going to happen to the breed first. We have more breeds of dogs than any other species on earth. We’ve got over 500 separate breeds of dogs. Out of the 500 separate breeds of dogs I’ve never heard of one that’s been lost due to inbreeding. Not one.

Dale Malony: Would you say in the wild that dogs line breed?

Dr. Padgett: Well sure. Ha! Ha! Of course they do. What the wolf does is he kicks the boys out and keeps the girls. That’s what he does. And so do the pack dogs, they kick the boys out and then the boss dog, the alpha dog, will kick the other dogs out. But he doesn’t kick the girls out. He likes the girls. The evidence is not clear at all. There are three real reasons that they argue against inbreeding.

The first reason is the chance that a gene that’s in that family is present in a pair of dogs within the family rather than in a dog outside the family. Even so, if a dog has one gene and you mate that dog with parent or sibling for any one gene, the risk of producing a defect is 12 and a half percent. If you talk about any five genes, five genes total, the risk of producing an effected puppy when mating between the same set, mother/ son, father/ daughter or brother/ sister is 45 percent. Okay? What’s the carrier frequency of Hip Dysplasia in your breed right now, I think it was 50, isn’t it?

Debbie Martin: 59 diseases, 39.1% Hip Dysplasia. (only 4.9% affected)

Dr. Padgett: A carrier frequency of 40% …so right now, with mostly out crossing your dogs, you’re just as high as inbreeding for five separate diseases, right? Five percent difference. In some breeds, it’s already higher. In Newfoundlands it’s 66 percent, the average for the whole breed, which is 20 percent higher than the average for the closest inbreeding you can do. So that’s one point.

The second point is that you decrease the general adaptability of the dog or any animal by making them homozygous, by making all of the genes paired. Because genetically you’re more adaptable if you have a big "A" and a little "A" than if you have two little "A’s" or two big "A’s". This is theoretical, okay? What I say is, dogs are the most adaptable species on earth. We’ve done anything that we want with them. If they were people, we would have people weighing from 30 pounds to a ton, or a 100 pounds to a ton. How much more adaptable can a species be? And all of those dog breeds, all 500 of them, were inbred to become a breed, every one of them had to be inbred to become a breed. So we have never lost one due to inbreeding and have 500 of them now.

Have you ever thought about why, when you breed two Shepherds together, you never get a Labrador? It’s because in the inbreeding process, all Labrador genes were excluded to the extent that there’s not enough of them in there to form a Labrador. The only way you can do that is to inbreed. So you inbreed on a certain set of characteristics, exclude all of the characteristics you don’t want, and then you have a breed of dogs that reproduces itself. Every breed of dogs, if it’s a breed, in fact, was inbred to the extent that they exclude all other breeds. And there’s no other species on earth like it, no other group of animals like it. I mean, how much more adaptive can we get? So I don’t buy that theory.

Inbreeding depression is the third major point that they have. If you have inbreeding depression, you will reduce, for example, the number of puppies per litter, but you don’t term everything in a dog bad at the same time. There are a couple of examples. The only paper that I’ve found in the literature on inbreeding in dogs was written in 1970 and that paper showed a decrease in the number of litters produced from about 75 percent to 25 percent in seven consecutive brother/sister matings.

So, the fact that inbreeding depression can occur is real, but what they didn’t do in that study was select healthy animals for inbreeding. They inbred based on relationships only. If you look at inbreeding depression in the work done by Helen Dean King in Wistar Rats, she inbred 20 consecutive sets of brother/sister matings, and they are now one of the most used research rats in the entire world. They are all over the place. Twenty consecutive brother/sister matings! When she inbred, she selected healthy animals. So if you inbreed and want to avoid inbreeding depression, then you need good husbandry. You need to pick good breeding stock, and then you will avoid inbreeding depression.