The use of limestone (calcium supplement) is increasingly common as an ingredient in the formations for complementary mineral feeds for rearing animals and poultry. This scientific feed contributes to rapid, healthy growth. Given that bones are almost entirely made from calcium and phosphorous, it is logical that these two elements are the main components of mineral feeds. The main sources of calcium in mineral feeds are lime with a high calcium content (minimum CaCO3 content of 97%), either finely ground or pulverised, bone flour and bicalcium phosphate, in that order. Normally calcium is added in a greater proportion than phosphorous. For example, optimum production from a milk cow corresponds to 2.7 g of calcium and 2.0 g of phosphorous per litre of milk produced. In poultry farms, lime is eaten in granular form. The grain remains lodged in the birds’ crops with the purpose of helping to grind ingested food. There is a definite preference for calcium carbonates (CaCO3) due to the fact that the calcium is absorbed by the birds, strengthening egg shells and improving their formation. Dolomitic stones are not used as little value is given to magnesium (Mg). Generally speaking, this element is provided as a laxative in the form of SO4Mg (magnesium sulphate - Epsom salts).