Meaning of the abbreviation used.
P…. Protein
F….. Fat
f….. Fiber
C….. Carbohydrate
Dm… Dry matter
M….. Mineral
cr ….. Conversion ratio

All of theses have significant role to play In the formulation. I will explain in details.
The higher some of the nutrient value the unreliable that Feedstuff is eg the higher the fiber, the unreliable the feedstuff is.