Bone mineral changes in dairy cows. The effect of low and high calcium feeding during the high yielding period.

Bone mineral content in two coccygeal vertebrae of 14 cows of Swedish Red and White Breed were investigated using the dichromatic photon absorptiometry. The investigation started at parturition and continued for 120 days. Each animal received a controlled amount of hay, ensilage and concentrate, and the milk yield was measured and registered. Seven cows (group L) received Ca and P close to the ARC standard. The other seven cows (group H) received a 30 % higher amount of Ca and P (15–20 % above Swedish standard) than the ones in group L. The bone mineral content in group L decreased by 10 % up to 90 days postpartum, and thereafter increased. In group H, the mean bone mineral content increased.