Hi, I used to work at an animal shelter back in college.
Did they rescue mostly cats and dogs, or were there every any wildlife there as well?
Mostly cats and dogs. Have you heard of no-kill shelters?
We have a no-kill shelter in our town, of course they still have to euthanize some sick animals.
That is terrible. Such shelters should not exist! 
In the US there is no government run organization that provides oversight of the shelters.