Maize silage contains low levels of calcium, sodium and magnesium.
Supplementary mineral recommendations are not absolute for all situations, but reflect:
Calcium (Ca) = Limeflour (35% Ca)
Sodium (Na) = Salt (39% Na) or sodium bicarbonate (27% Na)
Magnesium (Mg) = As magnesium oxide (52% Mg), chloride (12% Mg) or sulphate (10% Mg)