All farmers will recognise a downer cow by the symptoms presented, and they know that this disease is brought about through a low level of calcium in the blood during a stress period.

This issue is commonly called milk fever and the cow involved a downer cow. What farmers won’t always recognise is that the cows that present with clinical symptoms are just a small part of a much bigger issue. This is why most researchers into the disease will use terminology such as hypocalcemia, as this broader term better conveys the true issue (calcium deficiency), and the fact that the disease takes many forms and effects many processes critical to early lactation.

For every incidence of a downer cow there will be many more cases where the cow stays on her feet but suffers the wider effects of the deficiency. Calcium deficiency can commonly exhibit in such things as calving problems, metritis, retained fetal membranes, mastitis, poor immunity, poor conception and the list goes on. Few of these things are as dramatic as the downer cow, yet they are equally important.

THE BODY’S CALCIUM BALANCING SYSTEM

The majority of feed sources supply more than adequate levels of calcium, yet calcium is among the most poorly absorbed elements. The body controls calcium uptake very tightly as an imbalance can lead to serious complications. This is done through the release of hormones, particularly, parathyroid hormone and vitamin D (a hormone not a vitamin), and calcium storage is controlled by another hormone called calcitonin. The body’s hormonal system responds quickly to manipulate the available calcium level based on demand. This system works really well, provided the diet is right and the cow has not been subject to longer term deficiencies. And also provided they are not under or over conditioned cows, as these cows are not as good metabolically at regulating these hormones.