The Limestone flour 3 kg from NAF A rich source of calcium designed to supplement bone growth requirements. NAF’s pure Limestone Flour should be fed when there is a need for additional calcium in the diet to supplement bone growth requirements. It helps in muscle contractions, particularly of the heart, and it has a role in the nerve impulse transmission in the central nervous system. Perhaps calcium’s best known role is in milk production and it is vital that lactating mares have an adequate supply.