The hormones send signal to the mammary glands in the body for it to start to produce milk to feed the baby. However there are times humans rely on to cow's milk. There are differences though between the two.Human milk has more whey protein compared to the cow yet they has less casein which is another type of protein compared to cow's milk. For carbohydrates, human milk is higher than the cow's milk. For the fatty acid, the cow's milk contains more unsaturated fat.