# Inbreeding Depression



## Megan Bays (Oct 10, 2008)

I've read where people have mentioned an inbreeding depression several times.

What exactly is this? How does it happen? When do you know you are have an inbreeding depression?

I pulled this quote from Don's latest thread on breeding:


Don Turnipseed said:


> Tony, what kind of cowdogs are you breeding? Couple of questions if it is OK. People believe breeding like this causes deformities. I have seen one but the bitch was over ten. How about all these mutations that people think run rampant? I haven't seen any. How about the overall health of the keepers and the energy level? Must be pretty darned good since they get the job done.


Thanks!


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## Don Turnipseed (Oct 8, 2006)

There are obvious signs and some not so obvious.
Obvious sings would be loss of size and loss of energy. 

Not so obvious (at first anyway) would be loss of fertility.

I think I am forgetting one but I haven't really thought about this for years. Much of what is written on the subject would lead one to believe you will see it in all the pups. This is not right at all. As the dogs are tightened up, it will affect a percentage while the others tend to get bigger and stronger. The second part of that is what is never mentioned....at least I have never seen it mentioned. It is one of those subjects where only the downside will elicite the correct response.


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## Ashley Campbell (Jun 21, 2009)

Here's how I see it. There was a herd of horses in northern Arizona in the 1970's. The BLM gathered up about half the herd and sold them off for population control. In early 1990, they did a similar round up. Since there are many natural predators for the horses up there, most ofl the weak offspring had been culled off. 
However, inbreeding depression was displayed with two brothers and their mother. We ended up with the two brothers and the mother, one of the colts was still nursing. His brother died soon afterward, the nursing colt died 4-5 years later and had numerous health problems and had aged at about twice the rate that is normal. The mother ended up being sterile after her two sons, she never had another colt.

Long story short, we had some of the originals pulled in 1970 to compare DNA with from the 1990 group. It was like Deliverance with how closely related they were.

Also in the group that was pulled was a stark difference in appearance. The newer group were stockier built, smaller, and all roan in color. 

So basically, if there's a defect and you inbreed, it can come out in spades, but it also improves those that are not defective. 
Some people are of the opinion that inbreeding causes "The Hills have Eyes" scenario, while it can produce the good or bad traits that the dog bred back to has, not necessarily a mutant.


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## Don Turnipseed (Oct 8, 2006)

This type of breeding brings out the recessives which is why it was the preferred method years ago. It brought things to the surface where it could be dealt with or, if it couldn't, you folded your hand early and got new stock. Now the popular method is to stay loose enough that the recessives don't manifest themselves as double recessives. That is all fine and dandy but it doesn't mean most dogs todays are not carrying one recessive that is being spead through a good part of the gene pool without showing until you go back to a relative some generations later. Happens all the time and the breeder is sitting there scratching their heads as to "where did that come from". After 11 generations(BlackJack), outcrossing is a scary proposition.


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## Don Turnipseed (Oct 8, 2006)

I thought of an excellent example of what inbred depression looks like looks like to give folks an idea. Some of the nature shows have shown it right on TV and didn't know what they were looking at. One show had several lion kittens. They kept focusing on one that wasn't doing well at all. As the pride moved to a new location, the kitten was falling farther and farther behind and finally just died. For those of you that remember that show, that is what it looks like. Weak, puny, just never does well.


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## Daryl Ehret (Apr 4, 2006)

What if they're only half-tired? :razz:


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## Kadi Thingvall (Jan 22, 2007)

Something interesting about the pedigree posted. I ran the numbers, and it was right at 20% IC 

A father/daughter breeding is 25% IC. So although the pedigree looks highly inbred, and 20% is a high IC, a father/daughter, with no other inbreeding, is actually higher. 

What would be interesting is to find out which breeding you would be more likely to see "inbreeding depression" in. And which one would be more likely to produce overall consistency.


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## tracey schneider (May 7, 2008)

Doesn't a lot of it really depend on selection...including lack there of?


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## Don Turnipseed (Oct 8, 2006)

Which pedigree Kadi? There are two posted. I never look at IC's but it has been awhile since any have come up at 20. I don't know how to figure them. The last fewm times the full bro/sis cross has been figured ith numbers varied but they were always in the low forties. If it is my ped, BlackJack comes from a litter with 100% survivabilty. Without looking it up, I believe the full bro/sis cros had 9 out of 11. That litter also had parvo at 8 weeks during the summer and only lost one so they are strong. This is why I decided to do the cross.


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## Don Turnipseed (Oct 8, 2006)

Daryl Ehret said:


> What if they're only half-tired? :razz:


LOL, yeh Daryl, that is exactly what people think happens. Nice photo. Is that one of yours?


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## Kadi Thingvall (Jan 22, 2007)

Don Turnipseed said:


> Which pedigree Kadi? There are two posted. I never look at IC's but it has been awhile since any have come up at 20. I don't know how to figure them. The last fewm times the full bro/sis cross has been figured ith numbers varied but they were always in the low forties. If it is my ped, BlackJack comes from a litter with 100% survivabilty. Without looking it up, I believe the full bro/sis cros had 9 out of 11. That litter also had parvo at 8 weeks during the summer and only lost one so they are strong. This is why I decided to do the cross.


The first pedigree in your recent cross I just did post. There is a lot of inbreeding going on, but the specific common dogs are a few generations back, which is probably why the IC was at 20.

You can plug the names into this site http://www.czerwonytrop.com/inb/index.php?full=ok&lng=en and it will figure the numbers, and show the percent by dog.


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## Nicole Stark (Jul 22, 2009)

tracey delin said:


> Doesn't a lot of it really depend on selection...including lack there of?


Yes, it does. With that counterbalance (selection), while not totally and completely an irrelevant concern, one can evade the potential for an inbreeding depression to occur. It's not really something that exists entirely on its own or rather just because prolonged inbreeding has been utilized but more than likely it's primarily driven by poor selection, or lack thereof, and environmental particulars which are shifted either deliberately or otherwise, thereby making it more likely to occur. No surprise there my only point is, is that inbreeding for phenotype clearly isn't necessary. 

Frankly, I'm a firm believer in if you know what you are working with from the start inbreeding isn't necessary but because it can be safer for those who have 20-30 years into a breeding program sometimes it makes sense to closely guard what you are working with by breeding that way. Consider the number of breeders any of us knows who has 20 years or more into their programs/lines - they're hard to come by. So what then are your options? Popular sires? Yes, that's often the case. To me, it seems logical that people naturally shift to inbreeding as their preferred strategy.

I've mentioned before that I've got a dog with a COI of about 0, yes that's right - a mutt. Yet, I've also posted pictures of 4 generations to illustrate that like really does beget like at least when pedigrees are stacked with dogs that represent the same or largely similar physical attributes. This dog isn't unique but rather a solid representative of the standard within this particular breeding program.

BTW Tracey my comments are not necessarily for or directed at you (seems to me you get the gist of it anyway) but rather for the general discussion based upon my own experiences and observations.


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## Daryl Ehret (Apr 4, 2006)

Don Turnipseed said:


> LOL, yeh Daryl, that is exactly what people think happens. Nice photo. Is that one of yours?


That's Pia, though she's actually an outcross. I think the tightest linebreeding I've ever done was something like a 4-5,4-4. Someone recently asked something like "what will I get if I linebreed this," and with the picture added, I responded "more mouths to feed." :razz:

Don explained quite a bit of this very adequately, but here's a shot at it in different words,

Inbreeding increases the frequency of homozygous (same-type) pairings of alleles at every specific loci on all chromosomes. Further inbreeding (beyond the F1 generation) puges more variations of allele types (which code for characteristics) from the gene pool. These reduced varieties of allele-types can be either beneficial, detrimental, or inconsequential.

Detrimental allele types are most times recessive, and not expressed until they have esablished themselves in homozygous form, in an individual organism. Linebred specimens are more likely to reveal any unwanted genes in their phenotypic expression, while the healthier specimens of such a cross are twice as likely to be free of unwanted detrimental recessives.

Natural selection acts on those unfit individuals by not favoring their survival success rate, thus purging the frequency of detrimenal recessives from the gene pool. Breeder selection from the trouble free specimens are double likely to faithfully reproduce themselves into their own offspring, and double likely to be free of the recessives that are unwanted.

The "loss of fitness" for survival when expressed in those troubled specimens proves them to be less suitable to their environment, is therefore called "inbreeding depression", and may result in characteristics such as smaller statured animals, reduced fertility, or any number of imaginable negative effects.

One term that is rarely ever mentioned at all, is "outbreeding depression", where a loss of fitness occurs from continual outcrossing. _Outbreeding depression_ is the result of udesireable genetic material which perpetuates and proliferates throughout the genepool, all the while camoflauging the presence of detrimental alleles with more dominant counterparts, until there becomes very few among the populace that are free of the probability of producing it.

In _outbreeding depression_, unwanted recessives have originated from either generations prior, or even from recent mutation that has yet to manifest itself phenotypically until a pairing is made where both parents are recessive carriers (F2 or later generations).

Inbreeding depression is a short term solution that can save future generations (thousands and more) animals from suffering the negative results of undesireable recessive pairings, and potentially save a breed through it's commitment when brought with careful consideration. It's important to remember that where there is inbreeding depression, _there is also purging._

Outbreeding depression occurs from the results of careless outcrossing, where the breeder's highest consideration may only be on the level of something like _'well I have this male, and a female...'_ This then results in the perpetuating of undesireable genes through multiple generations, while proliferating throughout the breed, affecting thousands yet unborn, and therefore in my opinion, the greater of two evils.


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## Selena van Leeuwen (Mar 29, 2006)

thanks for the link Kadi, I don´t know how to calculate the IC so it´s helpful.

The litter we expect this weekend has an IC of 21.875% I just calculated.
The litter we expect beginning of august: 6.25 % 
The litter we expect in september:14.85 %

the father-daughter litter we did last year is 25 %.

Pretty thight, haven't seen much depression though.


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## Don Turnipseed (Oct 8, 2006)

Daryl Ehret said:


> That's Pia, though she's actually an outcross. I think the tightest linebreeding I've ever done was something like a 4-5,4-4. Someone recently asked something like "what will I get if I linebreed this," and with the picture added, I responded "more mouths to feed." :razz:
> 
> Don explained quite a bit of this very adequately, but here's a shot at it in different words,
> 
> ...


Excellent post Daryl. Much better overview of what is taking place.

I didn't plan on being up this early but, Titan went on a killing spree about 4 am and blew the yard up pretty well. He is so much like his dad, Winchester. He can kill so fast that skunks don't even have time to spay. That is a good thing. I will take a garbage bag and shovel out when it is light and collect his latest victim before it gets hot. Why?? Because the evaporative cooler is on his side of the house. I was out there with a flashlight to see what the problem was when he went by me carrying the darn thing. If the skunk had sprayed him I would have known what was going on when I opened the door.


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## Don Turnipseed (Oct 8, 2006)

Kadi Thingvall said:


> The first pedigree in your recent cross I just did post. There is a lot of inbreeding going on, but the specific common dogs are a few generations back, which is probably why the IC was at 20.
> 
> You can plug the names into this site http://www.czerwonytrop.com/inb/index.php?full=ok&lng=en and it will figure the numbers, and show the percent by dog.


Thanks Kadi....and thanks for the link. I will take a look at that when I am awake.


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## Kadi Thingvall (Jan 22, 2007)

Selena van Leeuwen said:


> thanks for the link Kadi, I don´t know how to calculate the IC so it´s helpful.


I know how, and I'll still use a computer program every time  MUCH easier on the brain.


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