Currently, milk is mostly quoted as “dollars per kg of milks solids” (MS) or “cents per litre”. Some of us oldies still like “dollars per kg of fat”. When we were being paid for the fat only, “dollars per kg of fat” was fine, because more fat produced always meant more money received. Now that two components of milk, fat and protein, are paid for, and one component of milk, the litre volume, is charged for, a fat price alone, a litre price alone, or even a milk solids price alone, all send a distorted message on how one might get more money for an amount of milk. It is possible to sell more milk solids, by having a lot more fat and a lot less protein, and receive less money. It is possible to sell more litres, with a lower fat and protein test, and receive less money.
The most accurate, although cumbersome, method to quote milk price, is to quote all three component prices at the same time. So the MDF is currently receiving an announced milk price, with compulsory levies deducted, of $2.96 for a kg of fat, $7.42 for a kg protein, and minus $0.026 for a litre.