There are two types of fat that goes to make the FGM. One is the phospholipids and the other one is the cholesterol. If you estimate both in the milk then that would (though not precisely) give you some idea about the quantity of FGM expected.
pleased to joint you it is a very important question ...it is not the purpose of our research but.i thank that: to get 1 kg of FGM we need between 400 and 1200kg of raw milk ..( MFGM makes up an estimated 2-6% of the total fat globules ).it is very related from the quality of milk and its component in cholesterol+phospholipigs+ glycosphingolipids ... but we can collaborate ..