There is a public perception of the dangers of cow milk for children under 1 year of age. One reads this caution everywhere. However, the idea that a child from one day (365 days old) to the next (366 days old) can drink milk, and even what that means, is a bit odd. My son is 10.5 months' old, give or take a few days, and of course when I added cow milk to the Cream of Wheat that I had found in the grocery store, I was treated like a criminal. It seemed to me that that was a good way to introduce the growing infant to cow milk, and indeed it is.
Cow Milk Dangers
It turns out that the dangers of cow milk for infants under 12 months is a bit overhyped. Indeed, the main point is a suggestion that infants under 12 (or 9, 10, or 11 months, depending upon the country), is to not have it as the sole source of milk.
In the United States and the United Kingdom, it is recommended that whole cow’s milk should not be used before one year of age. In Denmark, it is recommended that whole cow’s milk can be introduced gradually from nine months of age and in Sweden from 10 months of age. The Nutrition Committee of the Canadian Paediatric Society recommends that whole cow’s milk may be introduced at nine to 12 months of age. -Whole cow's milk in infancy
A common rule of thumb in the US is no milk before 1 year, whole milk until year 2, and thereafter 1% or 2% milkfat milk. But even this may err on the side of too little milk fat for a two-year old, and does not address the actual amount of milk (which should be somewhere between 24 ounces and 500ml).
The main issues are twofold: digestibility, and nutrients. There are a few other side issues such as allergies (which affect a small proportion of the population) and lactose intolerance (which is affected by amount of milk). Most other purported issues have no evidence in their favor.
Nutrients in Cow Milk
In terms of nutrients, cow milk has more protein, and calcium, and sodium, and less iron; and increased calcium inhibits iron uptake. Also, only whole milk is recommended until the age of 2-3, when skim milk may be appropriate, depending on the child and their diet at the time. According to one study, children whose primary source of milk was cow milk at 9 months, had less iron in their blood, on average, than children breastfed, and children on infant formula (who had the most). A small number of children were actually anemic, so the degree of harm is fairly low, in any case.
Digestibility of Cow Milk
Infants are not able to digest cow milk at birth, and cow milk as an additive to food should not be given before 6 months. However, at that time, and certainly by the ninth month, Cream of Wheat with a bit of milk is something entirely reasonable and appropriate.
Adding Cow Milk to Food
At six months, an infant can digest a small amount of milk added to food, such as soups, porridge and the like. Foods made with milk such as pancakes, mashed potatoes, and scrambled eggs, are a great way of consuming milk, which is a functional food.
Transition to Cow Milk from Formula or Breastfeeding
Transition can be gradual, such as 25% cow milk to 75% formula or breastmilk. It also may be good to warm the milk, or at least achieve a temperature at which the infant is already adjusted, or in any case one they prefer (my son always liked cold formula/breastmilk in a bottle.
Of course not all cow milk is equal. One really needs raw milk, from healthy cows with healthy diets, a minimum of antibiotics, and no growth hormones, if at all possible. Most milk has additives, as well, such as milk powder (at the very least). Sourcing raw milk (and doing low heat pasteurization) is not impossible, and is really the best course of action.
Cow Milk vs. Toddler Formula
Milk is a functional food, and as such, well-marketed (and expensive) toddler formula is largely a waste of money.