Calcium in the Dairy Cow

 

The most serious problem involving calcium in the dairy cow is LOW levels of calcium. Milk fever, parturient paresis and hypocalcaemia are all terms that relate to low levels of calcium.
Hypocalcaemia simply means low calcium concentrations in the blood ('Hypo' = Low and 'calcaemia' means calcium in the blood).
Hypocalcaemia and Milk Fever: Very low levels of blood calcium cause obvious signs of milk fever in dairy cows...
Hypocalcaemia without signs of Milk Fever: Not all cases of hypocalcaemia result in milk fever. The term sub-clinical hypocalcaemia means that blood levels of calcium are low, but not low enough to cause obvious signs of milk fever.
Sub-clinical hypocalcaemia may cause problems including:
    * Poor appetite and low feed intakes
    * Sub-optimal milksolids production
    * Reproductive problems including metritis (a 'dirty' uterus) and poor conception rates
The outcome of hypocalcaemia (milk fever, or sub-clinical milk fever) depends on the age and physiological state of the animal. For an older cow that is about to calve or is lactating, clinical milk fever is a likely outcome. In young calves that haven't yet been bred and aren't lactating, calcium deficiency may contribute to rickets. Rickets from low levels of calcium is rare and more commonly result from a deficiency of phosphorus and / or vitamin D. Rickets is rarely seen in New Zealand cattle.
Milk Fever is the common name for the veterinary term parturient paresis. Milk fever is seen most commonly in cows that have just calved or are about to calve. Sometimes milk fever is seen in cows that have been milking for 8 to 10 weeks or more. Milk fever signs include weakness, the cow 'goes down' and is unable to get up again. Clinical signs of milk fever... If not treated, the animal goes into shock and will die.

There are three stages of clinical milk fever:

Stage 1:
    * Poor appetite / off feed and may be off her milk
    * Still on feet
    * Fine muscle tremor including slight head shake
    * Grinding teeth
    * Stiff legs, falls over easily
    * Dung output is reduced
Stage 2:
    * The cow has gone down, and is still sitting up on her sternum
    * The cow may appear drowsy, often with an 'S' bend or kink in her neck OR the head is turned back against her flank
    * The cow may extend her neck and drool with her tongue out
    * Her nose will be dry and her ears, tail and feet feel cool
    * Her eyes may appear dry and 'staring', looking vague
    * She may be constipated with few or no rumen contractions visible through the flank
    * Sometimes the cow is bloated
    * The heart rate is faster than normal and difficult to hear through a stethoscope or to palpate through the rib cage
    * Occasionally, the uterus may prolapse (turn inside out and hang out of the cow) if the cow has just calved
Stage 3:
    * The cow is down, but is lying stretched out on her side, she can't sit up on her sternum on her own. Rumen contents may be regurgitated out of her nose
    * Her limbs and head / neck are flaccid, and wobble when moved around
    * The cow is almost comatosed
    * The cow will die of shock within hours if not treated