Hypocalcemia is a common condition in the immediate postpartum period that affects dairy cows due to an increased loss of calcium in the production of colostrum and milk. This condition is met with detrimental effects to cow health and production, which can be seen clinically as milk fever or subclinically without apparent signs. Multiple studies have shown that prophylactic oral calcium supplementation immediately after calving helps subgroups of cows but not others. Our investigation into different dynamics of hypocalcemia provides a potential explanation for the lack of efficacy in some groups: they may not need additional calcium, or the calcium may be administered too early to be beneficial. However, the definitive answer as to why there is a lack of response of some cows to oral calcium, or all cows to subcutaneous calcium administration, is unknown: do these treatments interfere with calcium homeostasis or are we administering them at a non-ideal time?

Our objective is to evaluate how different postpartum calcium supplementation methods, and the timing of their administration, affect blood calcium concentration and regulators of calcium metabolism, specifically parathyroid hormone and calcitonin.