Influence of 1α,25-dihydroxyvitamin D3 on Calcium and Phosphorus Secretion of the Mammary Gland in Lactating Camels

Plasma calcium (Ca) and inorganic phosphorus (Pi) levels, and content of these minerals in milk were measured in six thirdparity she-camels after i.v. administration of 1α,25-dihydroxyvitamin D3 [1α,25-(OH)2D3]. This steroid significantly (P < 0.05) increased plasma Ca and Pi levels from 94.2 ± 4.1 and 54 ± 2.5 mg/l, before the first calcitriol injection at 0 h, to 108.1 ± 3,4 and 63.5 ± 2.4 mg/l 24 h after end of treatment, respectively. Ca and Pi levels remained high until the end of the test. Intravenous administration of 1α,25-(OH)2D3 significantly (P < 0.05) increased Ca and Pi concentration and secretion in milk. Ca concentration and secretion of milk sampled every 12 h increased from 1080 ± 30 mg/l and 1100 ± 64 mg/12 h at 0 h, to 1218 ± 34 mg/l and 1240 ± 57 mg/12 h after the second injection, respectively. Those of Pi increased from 732 ± 66 mg/l and 754 ± 61 mg/12 h at 0 h, to 840 ± 38 mg/l and 890 ± 56 mg/12 h after the second injection, respectively. Ca and Pi contents and secretion in milk remained high (P < 0.05) until 12 h after treatment. These results showed that 1α,25-(OH)2D3 might affect the mammary gland of lactating camels. It increased Ca and Pi contents in milk without, however, significantly affecting milk production.