12 mos. Babies can start whole milk at about 12 months of life. Though it's been traditionally recommended that only whole milk is appropriate, recent guidelines suggest low fat products are also fine for babies.
After 1 year of age. Whole milk should not be introduced to infants before they reach 12 months of age. A heat labile protein in whole milk is responsible to cause occult gastrointestinal bleeding resulting in anemia in infants. Less vulnerable though, toddlers also develop anemia when consuming a large quantity.
12 months. There are multiple reasons to delay introduction of cow's milk until 1 yr; an immature intestinal system cannot digest cow's milk and it lacks important vitamins such as iron and vitamin e. After this time, however, introduce cow's milk in a sippy cup (not bottle!). Toddlers should not drink more than 24 ounces of milk a day. Most of their calories at this time should come from table foods.