Parathyroid Hormone-Related Peptide and Vitamin D in Phosphocalcic Metabolism for Dromedary Camel

In mammals, phosphocalcic and bone metabolisms are mainly regulated by parathyroid hormone, parathyroid hormone-related peptide (PTHrP) and 1α,25-dihydroxyvitamin D or calcitriol. In camels, circulating levels of calcitriol are 10 times higher than those determined in other ruminants and further increase during early lactation. Calcitriol and parathyroid-related peptide stimulate intestinal absorption of calcium and phosphorus, and phosphocalcic excretion by the mammary glands to maintain breast milk production in the same species. These endocrinian features allow, on one hand to improve the uptake of calcium and phosphorus in the adult, and on the other, to meet the phosphocalcic needs during growth and development of the young calf, in a precarious medium. In camels, the status of vitamin D varies with the season and the postpartum stage. Hypocalcemia and hypophosphatemia due to a deficiency of vitamin D are responsible for many bone disorders which could be corrected by a diet rich in calcium, phosphorus and vitamin D.