Similar to an earlier post, some drive through parks in the states also have the option of buying feed pellets. The one drive through I really like is Fossil Rim in Texas but I do not like very much the pellet part - it makes many of the animals beg. Some also stick their heads in the cars which as someone else stated seems dangerous. The two times I visited on my own I did not buy feed. However the last two times I went with my cousin who purchased feed. I did take the opportunity to get some humorous closeup photos of a head in the window, but I still think I would prefer if they would not sell the feed.
At Out Of Africa in Arizona, they give you carrots to feed from a safari bus that they drive, but you are only allowed to feed camel or giraffe (no zebras or antelope or ostriches). The fun part is, they encourage you to put the carrot in your mouth and get a giraffe or camel kiss. May not seem hygenic (I have not done it myself), but it makes for a fun picture!