There was this article, i can't remember though about that singapore zoo has a agreement with many zoos of the world they mentioned about the young elephant bull Sang Raja going to koln, Inuka the polar bear though he hsn't left and Palong the elephant bull that went to Rotterdam which is now unfortunately dead. Anyway on to the main point it said that singapore zoo is a like you said not a massive interchange but quite big to some extent that they are a a extremly succesful zoo when it comes to breeding. It also mentioned that San Diego zoo and Sydney's Taronga zoo are another two extremly successfull breeding pitstops.
just saying.
Palong was a shame, an extremely handsome bull with great breeding potential. Unfortunately he fell into a ditch and broke his leg and had to be euthanized.