Described is an intra-mammary teat sealant and a corresponding method of forming a physical barrier in the teat canal of a non-human animal for prophylactic treatment of mammary disorders during the animal's dry period. The method includes the step of infusing a bismuth-free teat seal formulation into the teat canal of the animal. The method also prevents the formation of black spot defect in dairy products, especially cheddar cheese, made from the milk of animals so treated.