# Baby mice: growth stopped and tail looking skinny.



## lindberg4220

Don't know what it's called in english, but i wonder if any of you have any info on such mice, especially if it's heritable.

I know it's a genetic defect, and that it's called "mini-mice" in Denmark. 
The babies stop growing around 2-3 weeks, have a poor immune system, their tail starting to look like beads on a string. They usually die before weaning or about that time, some live 2-3 months.

Any info on this defect is appreciated!


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## moustress

This is most common with satin mice, but it can happen with any kind of mouse that has been inbred excessively. There's an example below. This little mousie is still looking relatively healthy, several others from this litter have already died. It's the result of harmful recessive genes. Satin mice came from radiation experiments back in the 50's, and the meeces were inbred to were inbred to stabilize the satinization as a stable recessive characteristic. they tend to being anemic, have troubles digestiing food, and if they survive past two or three weeks, they are stunted. It also happens more often in any of the more exotic types of meeces such as long haired, curly, or any other special type. Of course, getting mousies from an established breeder can help prevent this kind of thing, but recognizing the signs of inbreeding is an essential part of breeding healthy mousies from pet store stock, or any other source, for that matter.



Here's an example of what I'm talking about, I call these pintails.

Things to watch for: Wrong head shape; it might appear like a buffalo head. Body bunchy or hunched along the back. Rear end that looks boxy. And then there's the tail, which I think is an indicator of the general vitality of the mousie. A little stick tail on a boxy butt is very, very bad. The sort where the the segments appear as if strung on beads, such you mentioned is the worst. I won't breed a mouse with a skimpy looking tail. These things in addition to general signs of good health such as clear eyes, healthy coat, alert and active behavior are all things to look for when choosing a good mousie.


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## WillowDragon

I believe only satin mice in america came about that way, english satins are not prone to any of the illnesses you describe.

Willow xx


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## Cait

Satins in the UK did come from labs but are not related in any way to the above problem, it can happen in any variety of mice and is no more common in a certain type.


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## WillowDragon

I imagine it must be a deficiency of something?

Willow xx


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## Jack Garcia

WillowDragon said:


> I believe only satin mice in america came about that way, english satins are not prone to any of the illnesses you describe.
> 
> Willow xx


Neither are show-quality satins in the US. It's only in petstores that you find stock the way mousetress describes.


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## moustress

It's genetic, and is much more common in satins in the US, but can happen in any kind of mousie. The example I showed is a diluted blue baby of about three and a half weeks, and came from a pairing of a pet store mousie who, in and of himself, is quite healthy. He carries satin and produced a healthy litter the first time around; but one of the young boys was precocious and nailed mom and two sisters at the age of just barely over 5 weeks old. there will be only five keepers from those 'oopsie' litters, and they won't be used for breeding. This is emblematic of why it's not a good idea to inbreed on purpose unless you are very sure of the integrity of the genes you are working with. Angus, the buck from the pet store, and Deep Blue the doe he was paired to are going to be paired up again very soon, as he is a very nice angora long hair, and like I said, is a very healthy mousie. Eventually I want to take another stab at producing blue tris.

With satins, it's more than just the visible defects, there's a problem with the digestive tract, reduced fertility, reduced life span. While all my satins came from pet store stock, I now have a very healthy line of satins. It took awhile, but it's not impossible. I considered it a challenge and as I had no breeders in my area it was a challenge I couldn't avoid, as I love mousies.

And it's not just in pet store stock; I had the same problem with a mousie from a well known West Coast breeder. No one is perfect.


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## WillowDragon

Is this defect visable from birth?

Willow xx


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## moustress

If you cull the littlest ones, you probably won't ever see one like the one I posted. It's generally pretty obvious by the time the eyes open, and sometimes before that. I used outcrosses to my healthiest standard mousies to help weed out the bad recessives in the satins. I still occasionally find one or two pintails in a litter of satins or lang haired meeces. It's a good argument for keeping a written record of all pairings and the results of those pairings.


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## lindberg4220

WillowDragon said:


> Is this defect visable from birth?
> 
> Willow xx


No, the earliest we have seen it in DK is around 2 weeks from birth.


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## lindberg4220

moustress said:


> If you cull the littlest ones, you probably won't ever see one like the one I posted. It's generally pretty obvious by the time the eyes open, and sometimes before that. I used outcrosses to my healthiest standard mousies to help weed out the bad recessives in the satins. I still occasionally find one or two pintails in a litter of satins or lang haired meeces. It's a good argument for keeping a written record of all pairings and the results of those pairings.


Those babies wont live much longer, they are not sold and will be culled as soon as they get sick. And obviously they wont live long enough to be bred.


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## WillowDragon

I always cull obviously underdeveloped runts from day one (If they don't die naturally, which they usually do) and any pinkies that don't thrive in the first week... but that doesn't generally happen with my stock at the moment (Used to happen to me more many, many years ago when i bred a few litters of pet shop stock)

If I ever got a mouse that started to look like that i would cull straight away, and not not breed from the parents again. Luckily all my bubba's are fat and happy by that age.

Willow xx


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## WillowDragon

I have some litters that are just 4 weeks old, far too small (I have a thread about them, Mini Mice) and have literally only just developed thin ill looking tails.
As in, they looked okay last night, and i've just checked on them now and i can see bones in some of the tails.

They are active, running around like proper young mice and eating and drinking well.

I thought the litters problems with growth came from the mothers being very bad for the first few days of life, because when i placed them with a nanny, they did improve... but now it seems it may be genetic???

I was planning on breeding the parents again and placing the newborns straight with a nanny to se if they are ok, i may still do this, i'm not sure. The parents are my best typed mice i don't want to lose them from my program.

Willow xx


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## Megzilla

I had this in a few Yellow Broken+Self standard mice in the past. It only happened to babies that came from my past BEW doe. I would say it is genetic though, poor satin line?


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## moustress

I've seen this probem in standard and satin mousies, but it's more common in satins. I rarely see much of it any more, but it's a cumulative problem that involves harmful recessives, so outcrossing in lines that have shown the problem are the way to go. Once I got Pudge, a very robust male satin buck, and bred him to my healthiest does, I have had very little of this sort of thing in my satin lines. Recently I had a few from litters from sisters and brothers (accidental), and I did eventually cull the ones that remained after a few died on their own. Any line can suffer from excessive inbreeding, and the more unusual the breed, the more likely this is to occur, in my opinion. For that reason, I no longer breed any of the curly meeces that show up occasionally, and I no longer breed long haired to long haired for the same reason. I've seen some of it in my tri lines, but they are the only unusual kind of mousie I work with; that line is probably due for some outcrossing in the next couple of generations. I'll be looking for a couple of nice jumbo PEW's, I think, for that.


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## WillowDragon

Inbreeding cannot be the case for mine, because they were all outcross litters with mice from completely different breeders.

Since I got more healthy mice from the litter that was younger when it went to nannies I am going to assume that it was lack of early nutrition which caused the deficiency in these babies.


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## moustress

Yeah, I'd imagine that any kind of gestational stress might cause this problem as well, such as poor nutrition, illness on the part of the doe, exposure to toxic substances, and, for certain, premature birth to an underdeveloped young doe.


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## Jack Garcia

In human babies this is called "failure to thrive" and the causes are numerous but poorly understood in a lot of cases. That's why I'd cull any and all babies exhibiting these features. _edited to add: I mean I'd cull mouse babies, not humans!_

Very careful, selective inbreeding by itself does not cause these problems--inbreeding poorly does.


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## moustress

Uh, yuh...

Failure to thrive actually means something else entirely, Jack. It's caused by babies not getting the physical contact and affection that they need in order to take nourishment in adequate amounts to support growth and development. It can also be caused by lack of adequate nutrition in and of itself. This sort of thing has no relationship to birth defects caused by inheritance or adverse conditions during gestation.


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## Jack Garcia

Nope. I'm afraid you're misinformed again. Failure to thrive has no single cause and no single treatment: http://kidshealth.org/parent/food/weigh ... hrive.html Instead, it describes a general condition of...well, failing to thrive. It is also seen in dogs (puppies). It's a catch-all term for when babies just don't do well and the reason isn't fully understood.

The same applies to mice. Regardless of the complicated underlying causes, and regardless of specific nutritional, neurological or physical ailments, once they're born if they are sickly in general and fail to thrive, then they're failure to thrive babies (or mice). Look up "failure to thrive" in any medical journal (or even on Google) and you'll see.


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## moustress

Ah, so, honorable mousekeeper Jack, once again you have shown me to be wrong. We will both be so wise soon if we keep correcting each other.  I learned the term in a psychosocial context in anthropology.

(With apologies for a the mini-takeover of someone else's thread. again.)


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## Jack Garcia

It's not a take-over because this is directly relevant as to what's happening to the mice in question: failure to thrive.

Be well!


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## Kage Davies

OMG o.o

That, the picture on the first page, is EXACTLY what happened to my last litter, all except for two, and that's why I stopped breeding o.o. I had no idea it was a genetic defect. I thought I'd let them get some infection or bug or other. They keeled over, one by one. I never saw them eat solid food either, only ever powdered lactol (only two of the skinnies made it passed weaning). AND I culled the teeny tiny ones before their eyes opened. I culled the last two skinny bubs after 'weaning' because they weren't really weaned at all, and they were so painfully skinny (going by their tails.)

The other two are normal sized and healthy, though. They never showed any signs of being small.


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## Jack Garcia

Kage, I would say don't let that discourage you. As you've seen from this thread, nobody's 100% certain what causes it so it probably wasn't something you did or didn't do. It just sometimes happens.


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## Kage Davies

Aaah. It was my own sentimental fault, I only breed one litter at a time and I was very attatched to one of the bubs.

I would pick it up again, but I don't have time. I'm waiting till my studies are over and I get get a mousie shed .


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## Megzilla

as luck would have it (in the unlucky way) this is happening to 2 pups in my current litter. One's a longhaired satin, the others a standard ): poor bubbas


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## Autumn2005

I've had this happen to a couple of my litters. Actually, I've had 1-2 in almost every litter I've had. I even gave one of the pups to a friend and felt really bad when it died. So basically... try not to inbreed too much? Record which parents produce these pups and try not to breed them again? Why does it feel like I spend more time record keeping than playing with my mice?


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## Erica

If a satin carrier is bred with a doe that doesn't carry satin, can they still produce a baby like that? The picture on page 1 is very similar to the baby that I have posted about previously. He kinda has the boxy butt, but he is definitely growing. Overnight he sprouted a full body of hair, and seems to be growing, but very slowly.


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## WillowDragon

It can happen whether a mouse is satin or not... its not limited to that.

My litter (Its only been one for me, well three litters combined into one) was because the mums didn't look after them properly, I have bred the parents since then and fostered the babies off and had none of the babies at all come out like this.

W xx


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