Generally rescue groups go for 'the greatest good for the greatest number', so presurgical lab testing is not done, among other things. And then, issues are missed that matter. And avoiding pain medications is also cheaper; humane, not so much.
Mary
I'm in rural Paraguay. The rescue people are volunteers who open their homes to abandoned animals without any government or NGO assistance. Few vets here can afford any of the equipment you see in a first world vet clinic. Everything is done with the best of intention, almost no money and a lot of experience showing what works out best for the animals involved. My rescue vet has 30+ dogs on her property needing homes and spends her nights tracking down abandoned dogs in terrible shape - I know I adopted 4 of them and one (Max) is pictured below having 100's of parasite pulled out of him and a partial ear amputation, for free, in her own time after she spent hours searching for him.
There is too much reliance on pain meds I've seen this in the first world and compared it to here and S.E. Asia.
Last year she sterilized more than 550 cats and dogs, most had no home to go to, she donated her time we donated money for sterilization gear and anesthetic. I also try to donate fuel money, we estimate she's been responsible for 2,000+ sterilizations since I met her 3-4 years ago.
Those who took the various animals in are usually poor. Some have dirt floors and
no electricity or money for their own medicines. They feed the animals -often 20+ cats and a dozen or more dogs- before themselves... they truly are humane.
Limited pain meds are reserved for after major surgery like amputations, eye removal, car/motor bike accidents etc. I know because 5 of my animals (4 dogs and the one eyed pregnant cat below) I adopted from that same vet were found abandoned on roads with very serious (not minor) injuries and have had a leg amputation, an ear amputation, 3 broken legs fixed, an eye removed, etc, etc after being hit by vehicles/abused and she did it all for free.