What is a common dietary problem that leads to hypercalcaemia in dairy cows?
If the dietary calcium is high leading up to parturition and lactation this will result in high plasma calcium concentrations and will inactivate PTH (and activate CT). At the time of parturition the cow will normally go off her feed. The mechanisms for rapidly raising calcium levels are not there (as she has been relying on dietary calcium which she is no longer getting). This means when her calcium levels drop she will not be able to raise them again, leading to hypercalcaemia. The best preventative measure would be to maintain calcium release from the bone by feeding the cow a low calcium diet.