Check under the vet team here:
https://www.rzss.org.uk/conservation/meet-the-team
Professors, veterinary surgeons, veterinary nurses etc. Edinburgh zoo is not just your run of the mill local village zoo. So sorry buddy, I am sure you will understand if I still trust the word of these people on the matter and not you, a random person with distaste against zoos (not a big fan either to be honest). I mean this is not just any field as well, this is zoology. People usually get into it because they love animals and such. It is not completely impossible for someone in this field to lie to cover up but now it is just your personal distaste against zoos and human kind vs several very well trained people on the field... As I said, I am not a big fan of zoos either and somewhat undecided about conservatories (which is what "Edinburgh Zoo" actually is) but that does not make people working there terrible lying scum bags.
yea with a bunch of veterinary surgeons, nurses and zoology professors at their service, I am sure they were still not able to come up with a fake reason that your keen eyes were not able to spot immediately.