If you put an enchanted item (for example diamond sword with fire aspect) in the donkey's chest. it will turn into a regular diamond sword after killing the donkey (done this with the same sword).
Environment
vanilla minecraft survival/creative/adventure java 7u21 windows 8 using new launcher singleplayer world not opened in LAN
1: 2013-05-17_15.33.31.png having a diamond sword with enchantments. 2: 2013-05-17_15.33.41.png put the sword in the donkey's chest. 3: 2013-05-17_15.34.07.png killed the donkey retrieving a regular not enchanted diamond sword and the saddle+chest 4: 2013-05-17_15.34.10.png confirming the sword is really not enchanted
1: 2013-05-17_15.33.31.png having a diamond sword with enchantments.
2: 2013-05-17_15.33.41.png put the sword in the donkey's chest.
3: 2013-05-17_15.34.07.png killed the donkey retrieving a regular not enchanted diamond sword and the saddle+chest
4: 2013-05-17_15.34.10.png confirming the sword is really not enchanted