I am reading Marlin Perkins' autobiography and he states that at the St. Louis zoo (I think thats where it was) they had a 19 or 20 foot python (species escapes me at the moment but I think it was an African rock) that they force fed for 20 some years. It never took a meal on it's own. A slightly larger snake of the same species that they kept in the same enclosure ate regualrly and with a passion. They even had a picture. A dozen men sitting on a stretched out snake while two guys used a giant pinkie pump to stuff chicken down its throat.
If I remember I'll grab the book from home and get the details.