Have found with a bit of experimenting about 3 mts, dried up one of the mares a year ago, (I wean all mine next door to each other with an electric fence in between). I put them back together after about a month, the milk had all dried up but I found the 9mth old filly being fed again!! So separated them for just over 2 months and that did the trick, the mare then told her off!
I wean them gradually taking the foal back to feed to stop any mastitis, but increasing the time between feeds so the milk dries up slowly with little discomfort to the mare, its a bit more work but there is no stress and foalie is just the other side of a fence with its pals but has mum for comfort if it needs it.
