I have 2 new pups that will be 3 weeks old tomorrow. When they nurse, they stay on each of mom's teets for a few minutes, then move on to the next. After going through all of them, they keep moving, over and over, as if they aren't getting anymore milk out. They also have a hard jerking motion when they nurse, as if they are trying to pull out as much milk as they can. They're acting like they are starving. The thing is, mom is about 65 lbs. About 3 months ago she got out of our fence, which apparently was long enough to "find a friend", so we have no idea how big dad is. These new little guys are 6.8 lbs. at 20 days old, so I think they are getting plenty to eat. Should I supplement this early? Also, does anyone have any idea how big these guys will get? I can't seem to find any information online for weight at this age.