We wean with our catch pen. The cows and calves can see each other. One or two may even nurse if they get their heads through the panels and the momma lines up just right. I believe we are breaking the emotional bond more than the milk. After four days the Momma cows have all quit sleeping by the pen. We then move the calves to another pasture. Momma cows are not walking the pasture looking for babies. We keep a different cow or two with the calves. The calves do not really seem that upset by the process.