Calcium
Calcium is a one of the most important minerals in ruminants. It plays a key role in muscle function and immunity particularly around calving time.
Probably one of the most important macro minerals, especially around calving time. The cow will have a big demand on calcium before calving and especially during milk production. Older cows are more prone to issues with calcium around calving. This is due to their reduced ability to flush calcium from bone around calving time.
Sheep have a higher calcium requirement pre-lambing (4-0 weeks pre-lambing).
Calcium plays a key role in muscle function and immune function. Some breeds like jersey and guernseys may be more susceptible to deficiency.
Calcium also has complex interactions with other minerals pre-calving. For example we actually want low levels of calcium pre calving in the diet. High levels of magnesium and also low levels of potassium.
Also metabolic alkalosis will predispose cows to milk fever around calving time. This is where we must balance the dietary cations and anions in the pre-calving diet.
Milk fever or your down cow is the obvious clinical signs of the disease, but is only the tip of the iceberg within the herd in relation to calcium. Low blood calcium (subclinical milk fever has serious effects on cattle). This low blood calcium can affect muscles like the uterus and rumen. This may lead to poor involution (repulsion of the placenta) and lower dry matter intake (slower rumen function).
Calcium is one of the most important minerals around calving. It has several interactions with other minerals meaning that effort is needed to balance these in a cow’s diet. In grass-based systems this is why we put emphasis on pre-calving diets high in magnesium.
