Because mastitis usually occurs in lactating females, the best prevention is to make sure your dog is spayed — especially if you’re able to have the procedure done before her first heat. If you do have a lactating dog, ensure her bedding is kept clean, check her teats daily for signs of infection and clip her pups’ toenails.
Brum, Douglas. “Mastitis in Dogs.” PetPlace.com (April 14, 2011)
PetMD. “Bacterial Infection of the Breast in Dogs.” (April 14, 2011)
Ruben, Dawn. “Care of the New Mother Dog.” PetPlace.com. (April 14, 2011)