
Unlikely but they don't 'catch' mastitis. It's a condition that can happen. We've only had it once in one of our girls. And yes, it's important to rotate the puppies so they cover ALL the teats. Many time, my newborns avoid the back teats, preferring the middle ones - obviously if you have a big litter, they usually more or less drain all the teats. It can be that with a small litter, there they don't, that this happens.
And this is another reason why I didn't pile rich food into my pregnant bitches. Newborn puppies don't need lashings of milk - it's wisest to up the food intake once you see how many puppies she's catering for, and into the second week when the puppies are normally taking lots of milk.