YAll kosher milk products must derive from kosher animals
The milk of impure cattle and game (e.g. donkey milk) is prohibited
Dairy products may not contain non-kosher additives, and meat products or derivatives (for example, many types of cheese are manufactured with animal fats)
A number of pre-processed foods contain small portions of milk products, such as whey, which do not have to be declared on the packaging but may nevertheless render the product non-kosher, especially to bread