Hi Lori -- I'm wondering if you mean actually bagging up in the udder or if you might mean that the milk glands are filling? Don't know if you know, but the milk glands are located on the belly, directly in front of the actual udders. If you feel for the udder, move your hand straight ahead towards the mare's belly button. The milk glands are in that area.
Even when I know the due dates, I feel for those milk glands to start filling about 8 weeks before the foal is actually due. Their swelling precedes the filling of the bag. Then I know things are on target. Hope this helps. - karen :saludando:
Just had another thot -- There is a stage, before the milk comes into the udder, that is what we call "loosening," for lack of a better term. The udders start to sag a little & might give the impressioin of starting to fill, but they are just getting ready for that eventuality. This happens maybe 10 weeks before the due date, in my experience. If that's what you're feeling, that would put the mare pretty close to target date. Oh, and July 2 is my birthday.