Reptile & Amphibian Forums

After losing my colony of 400 breeder mice to a virus I decided to build the colony up (after disinfecting room and equipment from top to bottom) using Swiss Webster because I read many posts saying that they produce large litters. I started with 51 females purchased from HARLAN and held them to 8 weeks of age before starting the breeding. I knew the first litters would be small - they averaged about 8 per litter. My problem and concern is the second litters only averaged about 6 per litter. Has anyone had similar problems with Swiss Websters? Do they normally take a few litters to reach max litter size? If so, that would not be good because their useful breeding life is usually less than a year.

I feed them Harlan 18% protein diet - the room is well ventilated - the room temp is kept between 62-68 degrees - lights on timer 15 hours on and 9 hours off

Thanks.
Tomsey

Do you keep any rats or anything else with them? I went through a similar deal lost my whole colony to a virus after I brought rats in from someone else. Now everything of mine is direct from the labs, after losing my colonies I redid everything, the old caging was made of wood and it all found its way to the burn pile. I disinfected the whole room and started over with all new caging. First generation, all my rats and mice fresh from the labs, sucked they had skin problems small litters and very little production. Second generation came completely around, they breed like wild fire and no more skin problems etc. So dont give up, I think second or third generation and they’ll come around for ya, but wait till your second litters to pull animals for new breeding stock. Genetically I have always been told first litters are weak. Hope this helps Jason
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Jason & Danica
Have you ever been so close to tragedy Or been close to folks who have..Have you ever felt a pain so powerful so heavy you collapse..I've never had to knock on wood but I know someone who has..Which makes me wonder if I could if I ever had to knock on wood..And I'm glad I havnt yet because I'm sure it isnt good..Thats the Impression that I get. By The Mighty Mighty Bosstones.
Classic Dums

At Christmas time I bought 15 lab mice. (low budget). I bought 1.2 each of 2 inbred strains that are known producers of small litters (4 - 6 avg sized litter). I bought 1 female ICR, and 2.4 swiss websters. I also bought 1.1 hairless mice.

Of those mice I purchased only 1.1 of the swiss websters are even alive, in addition to 1.1 of one inbred strain, and 1.2 of the other inbred strain.

One of the two swiss webster males they sent me was a dud. One of his females had a litter of 3 pups.... and none of them had anything else for ten weeks thereafter. I switched to the other male and within three weeks had a big pile of pinkies (35 pinks out of four females). I've used those to create some additional breeding groups, and now I have six setups, 1 @ 1.3, 3 @ 1.2, and 2 at 1.1 (depending on maturation of the mice more than anything). In the oldest group of mice, they just started popping them out, but again, less than the desired amount. Always less than ten viable pups. The mice themselves are about 16 weeks old. Some of the other groups have also started having offspring, and they are having less than 10 babies each.

I did have a while that I was feeding a rodent chow that was a little low in protein and had some cannabalism, so that might have something to do with the low production I had for a while. But it's been a while since I remedied that. Even my low-litter-size inbred mice that are 8 months old are kicking out litters of 12 to 14, and my regular fancies are kicking out litters of 10 - 20. But the swissies are still kicking out low production litters.

I have one hybrid group, I crossed my largest-litter producing fancy strain (I call'em Toblerone) with the female ICR, and am now breeding those female babies to a Toblerone/swiss combo. Those mice are getting huge litters also.

Even my one ICR female, before she perished, had litters of 15 - 20 each time.

Either the hype is just that, "hype" or the swissies just won't produce for me. If I had my druthers, I'd get ICR in the future. (can't afford it).

Since I have fancy strains that produce in a similar manner to the swiss websters I'm not too worried though. Why pay extra for some special strain of mice when your specially bred mice do the job so well anyway!?
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~Sasheena

Kit, Kaboodle, Tantilla, Tantillas, Lightning, Kinkee, Maple, Licorice, Castle, Bishop, Queenie, Jester, Pandora, Phantom, Aphrodite, Athena, Hermes, and Lady

I get a lot more production in the summer than in the winter. Wait a couple of months and see if production goes up considerably. I understand that day length has a lot to do with it. Also, when kept just a little warmer, more energy can go into producing babies than keeping warm. My swiss websters produce great--I usually get litters in the 13-18 range (in summer) and even had one as large as 28! (very small pinkies, though). As long as they don't get too hot and the males go sterile, a little warmer works better for me!

On another note, lab mice are raised in sterile conditions--thus, they often have disease problems when exposed to the outside world. Their immune systems have never had to deal with ANYTHING before!

A guy I used to work for bought and sold A LOT of mice. When he couldn't get them from his usual source, he would buy surplus lab stock. There were always a lot of losses with these because they couldn't handle the verious pathogens that were around.

Rodney

Excellent point about immunity. Lab strains are raised under very strict condictions so that they won't have infections or diseases that could corrupt experiments. They are also inbred so that they will all react the same to the experiment, not because inbreedeing produces better strains. The most that can be said for lab strains is that they are stable, i.e. most defects have been bred out of the strain and that they breed true.

DeMak