God only can answer this question with exact composition. If at all some one can find out the exact composition of FCS then it will become defined media. However you can find the list of major components in " culture of animal cells by Ian Freshney"
I don't know about exact composition of FBS, but check this out http://www.labome.com/method/Fetal-Bovine-Serum.html
FBS contains ~100 mg of immunoglobulin per liter, growth factors and hormones, binding and transport proteins, factors for spreading and attachment, aminoacids, vitamins, trace elements, fatty acids, lipids, protease inhibitors.
Then Google for "FCS FBS aminoacid" key combination and so on, for example to get more specific information about composition
God only can answer this question with exact composition. If at all some one can find out the exact composition of FCS then it will become defined media. However you can find the list of major components in " culture of animal cells by Ian Freshney"