I was advised by the midwife at the hospital that you shouldnt give cows milk until 1 year old for 2 reasons, firstly because there is not enough iron in cows milk and secondly because the protein in cows milk is not easily digested by the baby....for your info this is what i have read
Babies who are exposed to cow's milk before their first birthday are more likely to be anemic, have diarrhea or vomiting, and/or experience an allergic reaction (the proteins in milk are more numerous than those in other milk products, such as the yogurt). The excessive protein load in cow's milk can also overload a baby's kidneys. It is deficient in vitamins C, E, and copper. It is harder to digest as well, often causing intestinal blood loss.
of course like anything there are differing opinions and at the end of the day you have to do what you want