Inbreeding in feeder rodents

[saleengrinch]

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

[speakeasy_serpents]

“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.

[owalreptiles]

@chesterhf

My biggest gripe with this argument, is “how do you know they only got stronger?”.
Do you have a control group of outbred strains that you’re comparing to?

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

@chesterhf

What is the criteria here?

More offspring, physically bigger, less health issues.

@chesterhf

Are you documenting size of each litter, weight of each mouse at weaning (21days), reproductive lifespan, % of mice that need to be culled for health reasons, body condition, male/female fertility and and if any of these things gradually changed or decreased with over 15+ generations would you know? Or is it just that these mice/rats are producing enough offspring to meet your needs and seem to be healthy enough.

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.

@chesterhf

People always jump to malformations like extra limbs or deformities as the outcome of severe inbreeding, and while they can be, in reality it’s much more likely to be subtle things like failure to thrive, higher rates of cancer, decreased fertility and reduced immune function. The latter would be one of my large concerns, as exposure to a pathogen can easily wipe out an entire inbred colony because their immune function is severely decreased.

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.

[saleengrinch]

@owalreptiles

I know because of my personal experience. Yes high homozygosity can have issues, but it can also have advantages.

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.

[t_h_wyman]

@owalreptiles

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.

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.

[owalreptiles]

Nope but I can still report observations made while they were still alive. There could of been unseen issues, maybe some needed time to mature, however zero evidence of it. I just saw the observable conditions of the animals improve as the generations went on.