Quote Originally Posted by frankykeno View Post
I would assume (having never really studied this part of rat care) that like any mammal, rats will get their milk coming in just prior to actually giving birth. Also like most mammals, active nursing by young will trigger milk production. It's been shown even in human females that have adopted infants, that we can begin to produce milk in a limited way, without ever having been pregnant in the first place, simply by the action of a constantly nursing baby.
Actually, from my knowledge on the subject (which isn't expert by any means), I don't think the phrase "in a limited way" is very accurate here. I've heard that many women who decide to breastfeed an adopted baby are able to produce enough milk that their baby does not need other supplements. It does take more time and effort to build up the milk supply than if the woman had been pregnant. There are also many who aren't able to produce enough to be a complete diet, but it may still be a very significant amount of milk. I think it is tremendously cool that this is not only possible, but can be extremely successful.

Anyway, back to rats. I agree with Joanna's assumption that the pregnant rat is almost certainly producing milk at this point, and even if she weren't there might be a pacifier type of effect.

I do think there is some concern for the unborn babies. I think it may have been Connie who posted a link recently to some studies about this, and if I recall, it said that if there is much difference in age between the babies, the younger litter will suffer because a nursing mother's nipples are changed by nursing, and if she has 2 week old babies (using that as an example, I don't remember specific ages if they were mentioned) nursing on her when her own young are born, the tiny newborns may not be able to latch on properly to the nipples that have adjusted to the stronger suck of the older pups. Maybe Connie or whoever it was can find this for us again.

Also, getting back to what I know from my breastfeeding days, nursing causes the production of pitocin which is the same hormone used to induce labor. So I guess it could possibly cause a premature delivery.

It sounds like neither one of these would be a problem as long as the 2 mothers were very close in their due date, but I'm really just speculating. I'd love to hear someone with more concrete knowledge chime in. Or for those who do the group mothering thing with their rats, in your experience does it appear to cause problems if the first litter starts nursing on the still pregnant mom? And how much difference in delivery dates do you usually have?