problem with KO litter survival

[soobs100]

Hi

I am trying to breed a colony of knock out mice in C57BL/6 back ground. The animals are maintained in a ventialted caging system. The problem I encounter is only 10-20% of the litter survive. I have tried both keeping the male in or taking out with the pregnant female to check if that helps in the survival of the pups. Usually if thepups that are alive the second day survive. I counter the problem in hetero x hetero breedings as well. Last week, I tried to use Balb/c as a surrogate mother. Two of the litters survived more than 5 days. but unfortunately the mothers bit the pups after 5-7 days which I have not observed even in BL5 mothers. i would appreciate all the help how to increase the litter survival.

Best regards
subbu

[biaani]

Problems of low survival are most common with the mother's first litter, when she hasn't figured out how to deal with the pups. But it doesn't sound like that here. Could it be that the mice are stressed for some reason? Is there noise in the room, is someone opening the cage every day, are there rats housed in the same room? Such things could stress a mouse female and make her kill the pups. We had a similar problem when there was a construction work close to our animal facility and the noise made the mice freak out.

Also, I guess you have genotyped the surviving mice to see that it's not your mutation that's compromising survival, i.e. that KO and hets die more frequently.

[goundhog]

Usually we only have one pregnant female in the cage, so when the babies were born, it would just be the pups and the dam. The litter size is usually higher with young female (6wks- 3 mo old) , but the litter size also dropped after its peak of 10-11 pups per litter. Was the dam demonstrating a good maternal behaviour? (sometimes your gene-of-interest may affect the behavior as well, on top of survival) For the females bite the pups and the pups can walk around, you might want to put jelly food at the bottom of the cage and separate the dam and pups, seeing if the pups can survive.