What should we look for in a good dairy cow/heifier?
What type of testing does she need to have done? Does the milk need to be tested for anything for it to be safe to drink?
(I assume it's much like a goat. You milk into a cup, make sure it looks good, and go on. Filter milk and get it COLD! Make sure clean teets and healthy animal etc)
Some do, some don't. You would have to test your individual cow to know for sure.
Apparently the older breeds, like Jersey, and I'd imagine Dexter, produce milk we are, on average, more suited to digesting.