nesting material

She’s super pregnant and about to pop! I got her about 4 days ago and she didn’t look this pregnant when I got her, (I did not know she was pregnant until a few days ago) her nipples are very visible and i moved her into a nursery cage where she is nesting, but I do not know how far along she...

EDIT: This question isn't about rats who might eat such a large amount of nesting material that they're not hungry for the nutritious stuff they need. I'm not asking what nesting materials don't give deficiencies upon being a significant part of the diet. I just mean, what will digest fast...