Gradually or at once
After a baby is 12 months of age, and is eating a variety of baby foods, he can be weaned off formula
and start whole cow milk.
The weaning can be gradual over a week, in which more and more cow milk is mixed into the liquid formula each day. By the end of the week, the baby's drink will be mostly or all cow milk. Or one can wean suddenly, by making the formula disappear and just offering milk.