The typical dairy ration contains a mixture of forages and concentrates. The concentrate portion contains carbohydrate sources such as corn and a mixture of protein ingredients, along with minerals and vitamins. Nutritionists try to formulate a protein source to maximize milk production. In general, a protein supplement is the most expensive ingredient in a ration. It is important to understand how the forage program and rumen function help meet the protein needs of the dairy cow. There are two types of feed proteins.