Low Bone Remodeling Research Articles

Plasma osteocalcin concentrations in cows around parturition. The influence of a regular versus a very short dry period.

Plasma Ca, P, Mg and OC concentrations were compared between 2 groups of Holstein cows around 2nd calving. Thirteen cows were milked until their daily milk production was lower than 2 kg, which occurred 4 d before parturition. The control group (8 cows) was normally dried 8 weeks before the expected time of calving. Apart from the week following the initiation of the dry period where plasma OC concentrations were significantly lower in dried cows than in the control group (which would indicate lower bone remodeling in dried cows), no significant difference concerning Ca, P, Mg and OC concentrations were observed between the 2 groups of cows. This indicates that the only lack of 1 8-week-long dry period probably has no major immediate effect upon Ca and bone metabolism in young dairy cows given a convenient Ca and P daily intake. Nevertheless, the lack of the dried period might protect the cow against parturient hypocalcemia: the decrease in plasma Ca and P concentrations observed 12 h after calving was less intense in non-dried cows than in controls.

Relationship of Bone Remodeling, Oxygen Consumption, and Blood Flow in Bone

Blood entering and leaving tibiae of normal dogs and dogs in states of low bone remodeling and high bone remodeling (hypoparathyroidism, hypothyroidism, hyperparathyroidism, and hyperthyroidism) was analyzed for ten-minute 85Sr clearances, arteriovenous differences in oxygen content, partial pressures of oxygen and carbon dioxide, and pH. The arteriovenous differences in oxygen content of tibial blood were the same in high, normal, and low-remodeling states. 85Sr clearance was decreased in dogs with low-bone remodeling and increased in dogs with high-bone remodeling. The close adjustment of osseous blood flow, as indirectly determined by 85Sr clearance, with remodeling activity and the constant oxygen uptake indicate the importance of alterations in blood flow in meeting the increased nutritional demands of active tissues. These adjustments of blood flow through bone to changing nutritional needs suggest a metabolic factor linking flow to the tissue's need for nutrients.