A year ago I purchased some simonsen mice. I got 5 different strains (some for some fancy mice experiments). The swiss websters I got did reproduce readily, and had litters of eight or nine. As they acclimated and got to the second generation, i was getting maximum fifteen pinkies. They never improved, and eventually my swiss webster colonies got sickly and died. I also purchased one ICR mouse from them (they were preparing to discontinue or limit their production of ICR, so one was all I could get). I crossed the female ICR to one of the swiss males, and in turn crossed the female offspring from THAT litter to my own fancy strains that already had litters of 17+. My new strain often has litters between 19 and 22 babies. The one thing that baffles me about these mice, is that the babies are HUGE. They aren't tiny little pinkies, but instead they come out the size of some of my fancy mouse strain fuzzies! I remember when I was preparing to get the swiss websters I was told about their large body size, and was actually surprised at how small they were compared with some of my own strains. I have to admit that the swiss/ICR/Fancy crossed mice are the best I have. Big huge litters, huge babies, tons of milk, docile, never cannabalize, never bite, and even calmer than usual hoppers. They are also long-lived, the original fancy mouse I started that strain with, and several of his females only recently passed on, about a year after I put them into a breeding group. And there was never a drop in production until they hit the year mark.
Anyway, I know some people have a lot of luck with pure swiss websters, I didn't. But I also had a lot of problems with all of my Simonsen mice. The hairless mice each went blind in one eye, and 75% of their hairless descendants also go blind in one eye. The C57BL/6 (black inbred mice) had only deformed babies, even though there were not supposed to be any deleterious recessives in these guys. They sent me replacements, and those too produced deformed babies. The DBA mice (inbred) were good breeders but mean! They hybridized really well with my fancies however, and I've gotten the cutest mutation from their lines (dumbo eared mice). Again, they should have been homozygous in 99.997% of their genes, so there should have been no hidden recessives. It was an interesting experiment with the mice, and I think it improved my mouse colonies, but I have none of the pure strains remaining that I purchased in December '02.
