October 2020

The transition period is a stressful time for dairy cows and ensuring a smooth transition into lactation is essential for optimal health, milk production and reproduction. The onset of lactation increases the requirement for calcium (Ca) in dairy cows, and cows often experience low blood Ca, or hypocalcemia. While clinical hypocalcemia, or milk fever, presents with obvious clinical symptoms, subclinical milk fever can easily go unnoticed. Ca plays an important role in the body, especially for muscle contractions and in the immune system, and even subclinical hypocalcemia is associated with increased risk of other health disorders, impaired reproductive performance and reduced longevity. Understanding the impact that subclinical hypocalcemia can have on-farm is essential, and being able to diagnose subclinical hypocalcemia is required to understand if a farm has an issue, as well as to evaluate management plans to address the problem. Additionally, using a Ca bolus at calving is a strategy to deliver Ca directly to the cow and ideally prevent hypocalcemia. The rate at which a Ca bolus dissolves impacts its ability to deliver Ca when the cow needs it most.

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