I'm a vet student involved in shelter med and I've been following along with this discussion and quietly nodding along, but I felt like adding this in. Our shelter in the Northeast gets a handful of transports from the South throughout the year. Personally, our shelter does a lot to be transparent and we absolutely do behavioral and medical euthanasias. But the transport companies/Southern shelters are so incredibly sketchy. For each animal, we get the signalment and a single, often outdated puppy picture. Sometimes we'll get a little bit of a heads up about major medical conditions, but otherwise, we don't get any medical or behavior record until the day of when the animals are already en route, and often we don't get their full medical or behavior record until they show up with papers attached.
In our last transport of only five dogs, we received the records upon their arrival and found documented in their history but untreated: giardia, 2+ months of diarrhea, ringworm, kennel cough that started three days before transport, heartworm (yes this happens but to know and not tell us beforehand?), and bite wounds. And this is by far not the worst we've received. We've had one transport dog die in foster care despite specialty treatment at the vet school. Why this is even allowed by the transport company, or how health certificates are signed when the animals are in this state, I just don't understand.
I wish that the Southern shelters understood that they only harm their relationship with us when they send up dogs that never should have gotten health certificates. We stopped taking transports for a while because of the total lack of information shared ahead of time.