Calcium is the mineral with the highest content in animals. In addition to forming bones and eggshells, it plays an important role in maintaining the normal functions of nerve and muscle tissues. Phosphorus is mainly found in bones and is involved in the metabolic processes of many substances. Insufficient calcium and phosphorus content in the diet or improper calcium and phosphorus ratio will cause calcium and phosphorus deficiency in ducks. Ducklings show rickets, and their beaks and tibias are soft but bendable. Adult ducks have osteoporosis, lay soft-shelled eggs, thin-shelled eggs, increased egg breaking rate, reduced egg hatching rate, and even stop laying eggs. Ducklings have poor tolerance to excess calcium. If the calcium content in the diet exceeds 1%, the ducklings will grow poorly. Laying ducks must be fed feed with higher calcium content during the laying period to meet the needs of eggshell formation.

Most of the phosphorus contained in plant feeds (corn, bran, rapeseed cake, cottonseed cake, etc.) is phytate phosphorus, which is difficult for poultry to digest and utilize. Available phosphorus (non-phytate) that can be utilized by poultry Phosphorus) only accounts for 30% to 40%. The available phosphorus in inorganic phosphorus and animal feed (calcium hydrogen phosphate, fish meal, bone meal, etc.) is 100%. Calculate available phosphorus (%) in the diet = inorganic phosphorus (%) + plant phosphorus × 30%. The inorganic phosphorus supplemented in the diet should account for more than 1/3 of the total phosphorus. The suitable ratio and dosage of calcium and phosphorus for meat ducks and laying ducks are shown in the "Nutritional Requirements of Ducks" table.