Kraft does not own all the cows that supply their milk. Kraft, like most other large food companies, sources milk from a variety of farmers and dairy operations. They have contracts and agreements in place with farmers and dairy cooperatives to purchase milk for their products.
They have set up quality standards and guidelines for their suppliers as well to ensure that the milk they receive is of good quality and also ensuring that the cows are treated humanely.
In some cases Kraft also provide their suppliers with feed, technical support, or other resources to help them meet these standards and to help them to improve their operation.