title: Effects of a deficient magnesium supply during the dry period on bone turnover of dairy cows at parturition.
abstract: The bone activity and bone mineral content in rib bones resected from 33 dairy cows between 3 and 8 h after parturition were measured, and the effects upon them of a deficient supply of dietary magnesium (Mg) during the last seven weeks of pregnancy were studied. The cows were fed a diet containing either 0.22% magnesium (low Mg) or 0.82% magnesium (high Mg) in the dry matter (DM), and the potassium content of both rations was increased to approximately 4.1% in the DM to reduce the absorption of magnesium. In the cows fed the low-Mg diet a fall in plasma Mg concentration was observed. In the low-Mg, low-parity cows the plasma Mg concentrations at parturition were higher than in the low-Mg, high-parity cows, i.e. 0.83 mmol/l and 0.54 mmol/l, respectively. After parturition four cows in the low-Mg, high-parity group showed clinical signs of hypocalcaemia but none of the other groups did so. The bone formation in low-parity cows was significantly (P less than 0.05) affected by Mg supply, with higher percentages of both trabecular surface covered by osteoid and osteoid volume in the low-Mg group. In the high-parity cows no significant differences in bone formation were found between the low- and high-Mg groups. An inadequate Mg supply resulted in a significantly (P less than 0.05) higher Ca content in the bone ash of low-parity cows and a significantly (P less than 0.05) higher bone ash percentage in the bone of high-parity cows.
authors.affiliation: Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, State University Utrecht, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: van Mosel
authors.forename: A T
authors.initials: AT
authors.lastname: van 't Klooster
authors.forename: H S
authors.initials: HS
authors.lastname: Wouterse
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000033:anatomy & histology / Q000737:chemistry / Q000503:physiopathology*; D002118:Calcium / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D004032:Diet; D005260:Female; D006996:Hypocalcemia / Q000209:etiology / Q000662:veterinary*; D008274:Magnesium / Q000008:administration & dosage / Q000097:blood / Q000652:urine; D008275:Magnesium Deficiency / Q000150:complications / Q000503:physiopathology / Q000662:veterinary*; D007744:Obstetric Labor Complications / Q000503:physiopathology / Q000662:veterinary*; D010010:Osteoclasts; D010298:Parity; D010758:Phosphorus / Q000097:blood / Q000652:urine; D011247:Pregnancy; D011897:Random Allocation
chemical_list: D010758:Phosphorus; D008274:Magnesium; D002118:Calcium