Would like to know more about it
Okay, so this zoo (Ramat Gan Safari Zoo), uses the 'hands on approach', meaning that specialist zoologists and vets do a checkup on all animals every morning.
Important note, only specialists do this, the general audience and zookeepers are not allowed to touch the animals.
The way the checkup works, is that after the real nutritious breakfast, the zoologist comes in with treats (peanut butter, white cheese), and asks the animals to present a body part, like when you train a dog. Things like "show me your shoulder", "show me your tongue", and then they gently touch the body part with a plastic stick. Then the animal gets a treat.
This serves both as a physical checkup to check for injuries and diseases animals may hide (and social animals often do like to hide injuries), and it allows to administer medicine. Like, if an animal needs a specific pill only for him, the zoologist can put it in the peanut better. If it needs an injection, instead of touching the animal with a stick they just do a quick injection (most animals don't even notice the difference in my experience).
This way you can do all easy medical treatments in the animals habitat, without tranquilizing amd causing it stress. More complicated medical intervention obviously requires more.
What surprised me the most is how most animals recognize and trust their keepers, and so can do this morning checkups. This included tigers and crocodiles. Some animals are still not trusted enough, like Cassowaries.
With the safari animals, because they all live together and you can't call them one by one, it's a bit more complicated. What they do is observe the animals throughout the 3 feedings of the day, and if they see an animal suspicious of injury, they later lure it away from the herd, usually with something fun like a favorite food or an enrochment (the hippos for example love the water hose).
Then they can be observed alone, and if they do turn out to need medical help they are preferrably taken to a quarantined area where they can be treated, and if all else fails they are tranquilized and sent to the hospital, but this is usually avoided because tranquilization is stressful and animals could get injured while tranquilized.
If you have any more questions I'd be glad to answer!