Inbreeding in feeder rodents

Not the exact same as in, they don’t have an extremely complex brain that can have a ton of things go wrong that makes us slow and unable to function in society. Inbreeding genetics still work in the same ways though. Just not in as obvious of ways since rodents can’t speak.

I have put this topic in “slow mode” to promote thoughtful discussion and save it going back and forth with repetitive points.


Mood disorders more common in children of first-cousin parents, study finds | Genetic Literacy Project

This is not about rats, but since humans were brought into this discussion. I thought it might be a good read. I am finding it very interesting. Some of my family members a long time ago married first cousins and some of the mental issues did show up. It could happen to any species in my opinion. Even rats. I will leave it at that.


So the effects of inbreeding of first cousins were apparent after one generation. So I’m guessing the effects on actual siblings would be more profound after one generation.

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If you read the article it says there is a higher chance there are mental issues, but not in every case. I think it is a luck (or bad luck) of the draw in this case. For physical issues it probably takes a few, not sure how many generations it took for Charles II. His family tree is a wild ride though lol.

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Yes, thank you. Fingers moving faster than brain. LOL

This is a fallacious argument that is constantly thrown about when comparing two different organisms on the gross level when that is not the realm we are dealing with

Inbreeding effects are a genetic issue. And genetics is genetics is genetics. It does not matter is we are talking about humans or humpbacks or ball pythons or bandicoots or mice or moose

Inbreeding effects are the result of a loss of genetic diversity because there is no introduction of outside genetic material.

Mice and rats do not have some alternate genetic code that allows them to spontaneously generate genetic diversity de novo as a mechanism to combat inbreeding. Absent the introduction of unrelated genes (or the < 1 in ~30,000,000,000 or so chance of a perfect recovery mutation) you will absolutely develop inbreeding effects

Ummm… No, you most certainly do not see inbreeding effects in humans in one generation. Like with any closed system, it can take time for the effects to be know. Barring specific known issues (haemophilia, sickle-cell, etc.) five to seven generations is, typically, where it starts to become evident

That link is misrepresenting the actual findings of the study which were that offspring from cousin x cousin pairings may be at higher risk for common mood disorders. The important word there is RISK and in this contest it translates to ‘statistical chance’. This is not some “Eureka” moment however because it is simply confirming what is already known when it comes to inbreeding - i.e., there is a greater statistical chance of bringing together common alleles when closely related individuals mate. I mean… DUH! How do we prove a new recessive trait? By breeding two closely related individuals (parent x offspring, sibling x sibling) that we know are carrying the common allele.


Is this not then confirming there is a effect within one generation? If your odds are higher to develop a defect in one generation is not the higher odds a defect in itself?

At some point,* yes. Of course.

I am going to be sadistically Socratic on you and answer your question with a question LOL

If I take a pair of cousin snakes that share an Albino grandparent, am I guaranteed to produce an Albino from them??


Dr Wyman clearly I am at a disadvantage in this debate. You have a PhD and all I have is wit and charm. Cut me some slack here.


Not trying to put anyone at a disadvantage, just going with a different style of teaching here. Mainly because work reared its ugly head and I had to run so there was no time for one of my novellas.

Things are not on fire any more. Let me eat lunch and make up a couple figures and then I will be back


Fair enough Travis but for the record I read The Republic by Plato as well!

And now we return to our regularly scheduled programing…

So, my question:

The answer is very simple and straight forward - No, you are not guaranteed to produce a visual Albino in this case.

Why are we not guaranteed to produce a visual?

Our cousin snakes are both 50% poss hets, as such there is no guarantee that either of them are actually carrying the Albino gene.

Simple and straight forward enough.

But what does this have to do with that study and my assertion that there is no single generational effect?

Expand the example out. What if, instead of an Albino grandparent, it was a “Mental Health Issue” grandparent. In the same way we cannot guarantee a visual Albino from a 50% poss het Albino cousin pairing, so too we cannot absolutely guarantee that offspring from a 50% poss het MHI cousin pairing will have Mental Health Issue.

Now flip the whole thing upside down…

I walk into an expo and pick a random CH bush baby male from one random importer table and a random CH bush baby female from another random importer table. I also find a breeder that has a cousin pair of 50% poss het Albinos sitting on his table.

I bring both pairs over to you and tell you that if you breed them and fail to produce Albinos, I will pay you $1000. Of those two pairs, which has the higher risk of producing Albinos?

This then is what that mental health study is saying. There is a greater risk of the cousins producing an Albino when compared to two random individuals, but it is not guaranteed you absolutely will produce one.


My whole point was even at the first generation a human sibling pairing has a elevated risk of defects.


Above, you said results (not risks) of inbreeding are seen in the first generation.

I never denied that the risk was there. The risks of inbreeding with any sibling paring are also much increased, that is true regardless of whether the organism we are talking about is a human or a mouse or a ball python


I also said is the elevated risk not a defect in itself. But I digress, I concede Dr Wyman.

“Purebred, is just inbred spelled with a dollar sign”

Sorry this just popped in my head…when i was a kid I lived next door to a retired ranch hand…I mostly blame him for my love of animals. Reading this thread made me remember one of his many quotes.

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I’m comparing rodents multiple generations down the line to the first generation I bred.

More offspring, physically bigger, less health issues.

Documenting? nope. I was breeding rats for snake food, not running an experiment. However I can visually see these things happen and share my experience, such as. On average litters used to be about 9 babies both rats and asf, multiple generations down the line, average was about 17 for the rats ASF probably averaged 20 or more. When I walked in the room, you can hear rats with respiratory problems and/or see it. Nearly non existent after multiple generations. Given genetics aren’t the only thing that can affect that. Adults used to be about (_) this big and multiple generations they got about (__) big. I didnt weigh them, but is was visually obvious. Fertility was never an issue from the start, I only breed a given rats/asf for a year, mice 6 months, then they would be retired. no issues from the start with that either. Might be surprising but I didn’t have any rodents die to old age, so i cant speak for the lifespan.

I had less isues with some and the rest no evidences was shown for them.

I know because of my personal experience. Yes high homozygosity can have issues, but it can also have advantages. If i would of saw issues, i would of easily dialed back or outcrossed. Theres no advantage to making rodents with issues. Just kept making breeding groups out of the offspring of breeders that were doing the best.


I’ve had similar experiences as you Matt. I agree if your noticing big problems then you outcross. My rodent colony is fairly large. I started with a diverse group with animals from multiple sources. I don’t pick my breedings but I cull any animals with noticeable defects. When I cycling and adding breeders I always pick the animals that appear to be the healthiest. I do add new blood to my colony but not that often. Usually I’ll just pick around 6 females up from shows. But sometimes it will be long periods without new blood being added. The only time I’ve ever had bad noticeable offspring was when I first added mertins Red Devils to my colony. They were having eye issues so I just made sure not to put the mertins females in with visual mertins males. Problem was gone.


This goes back to what I said above, how would you know if the effect of inbreeding depression was not hitting these animals when they are culled before those effects can be manifest? Do those 17 size clutches hold true for a female that is two years old? Three? Do the adult animals even live to three, or do they develop cancer and ■■■■ out? Feeder breeders cannot answer these questions because they feed/freeze the animals before they even get to this point.

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