I haven't trained animals for blood draws (the tiger keepers have done that with a few tigers already) but I did put the fat back on a zebra (with beet pulp and feeding apart from the others) and on a P horse mare (that took a few years due to difficulties eliminating parasites and fighting wisdom that stated that old horses are naturally anorexic). I also stopped our Himalayan black bear's afternoon stereotypies via reduction in the number of feedings to one a day and by greatly increasing the time it took him to find his food, I increased the appetite on a caribou that hadn't eaten well for years, I found out through trial and error how petting emus stopped them from attacking and I could fetch an ailing calf from under the nose of a bison who I knew I could trust to not attack. If I had to convince the entire staff to try my guesswork until I got the results I was looking for, I would have failed. Because of stability, the horses know which hay rack is theirs in the morning, the hippos know that when I turn on the music it's time for them to go out on exhibit, each yak knows which door is theirs, the old brown llama does not need to be coaxed into the squeeze cage, I know by how fast the yaks come in how much hay to give them, I know that clumped feces means your animals are eating enough to put on weight, I know that our capybara's diet is still too rich and so on. Multiply that by 5 sections and you get people that know their animals inside out everywhere and who are constantly working on improvements. 8^) Many times it does come down to one keeper who realizes that there is a problem and then tests solutions until something works.