susang said:
Well I don't know what I"m doing wrong I had 1.3, one female never bred but was a good Mom. I started another colony 1.2 they did OK but first male very aggressive towards me, great Dad. So he got replace with son, the most I got out of that colony was 12-15 a month but had to remove wienlings, before the female would drop next litter. So if I took them out today, she would have a litter tonight and the other female soon after. Now my origianl colony has started eating some fo the babies, and 5 out of 15 were like mini-mice adult looking, acting, eating, but about the size of a quarter. I seperated those to see what happens. Just this past month I have had a hard time growing any to feeder size. I started a new colony of 1.2 white mice to see what happens, so far one is pregnant. I'm seriously thinking of keeping just the mine and the white and freezing the rest and starting another new colony :shrugs: susan
ps thanks again for starting this thread, I'm really learning a lot.
You need to rotate your females to keep your numbers up. Back-to-back breeding takes alot out of the females, and they should be retired after roughly 6 months. Any more than 7 litters, or so, and the numbers dwindle, attitudes become meaner, and they get aggressive towards the offspring. The males don't lose as much through the breedings, and can be rotated once a year or so, depending on the attitudes displayed and the production numbers.
FWIW...12-15 pinks per month from only 2 females is fairly good production. You're average 6-7 babies per female per litter, which falls right in line with very average litter sizes. Use more females. This accomplishes several things:
First, more females automatically results in higher monthly production, because you have more wombs producing. With a 3 week gestation, it is unreasonable to expect any more than 1 litter per month from any female.
Second, it lowers the aggression of the females, because they share the mothering responsibilities. Instead of each mother protecting and caring for her own young, they share the workload and develope a more tight-knit family unit.
Third, it takes pressure off of the females by allowing the male more breeding options. Much like humans( :grin01: ), the males want to breed constantly, even if the female is already pregnant. In a 1.2 colony, both females will get pregnant fairly close together, leaving the male with no outlets for 3-5 weeks at a time.
Finally, more females in a colony helps to produce more "staggered" litters. If you have a new litter born every week of the month, it doesn't take long for the freezer to fill up. Plus, you can cull partial litters, and allow more babies to reach larger sizes, without depleting resources or causing mammary tumors in the females by removing all of the offspring while she is lactating.
I know it's pretty easy...get a male and a female and let nature do it's thing. But for steady mouse production, you need to be aware of more than the physical aspects of keeping and breeding mice. There are limitations, naturally, to what females are capable of. Left to their own devices, mice are notorious overbreeders. But continued back-to-back breedings cause a TON of physical wear and tear on the females, and greatly reduces their effective reproductive life expectancy. They will certainly live longer than they are productive in a breeding colony. Worn out females simply can't produce the way a young, vibrant, and freshly weaned female can...
FWIW...I rotate females every 6 months, almost like clockwork. First week of September and first week of March, I get new females, and retire the previous breeders. I also have MUCH lower production numbers during summer months, when heat tends to ward off any desire for breeding the mice have...males included. This is the same schedule I have set up for my colonies in the pet store, and works well for both my personal and professional needs...
The gestation period is about the same. Litter size is usually somewhere between 5-14 babies on rats. (the litter size is usually on the higher end after the first litter and then they have lotsssss for a long time and then towards the end of their life they get smaller again) I think I have a couple newborn rats in the freezer if you want me to weigh them for a size idea 
