How do I know if the mare is producing enough milk? She seems to suck up her stomach when the baby is nursing and the bag doesn't look very full.
Make sure that baby is swallowing and nursing often. You can do an IgG test to make sure baby got enough colostrum. This is the first milk that is so important. Otherwise watch the baby’s weight, energy level and alertness. Babies sleep a lot but should have periods of awake time that are filled with running and playing. If all of that is normal then all is probably well. Of course, Nothing takes the place of a good veterinary new foal exam!