Milk Fever (Hypocalcaemia) in Dairy Cows
Milk fever (or hypcalcaemia) is the result of a reduction of blood calcium in the early stages of lactation. This is due to the cow having a sudden, dramatically increased demand for calcium to produce milk. In the newly calved cow, this sudden need for calcium comes as a bit of a shock for the body and it can take several days for the normal mechanisms required to regulate calcium levels to begin working efficiently . It is during this transition period that cows are prone to classical milk fever.
Cows that are further into their lactation are better able to cope with the shortfall of calcium by absorbing it from their bones and also the mechanisms by which calcium is absorbed from the diet are working much more efficiently.
Cows can be affected by milk fever both clinically (with obvious signs) and subclinically (more subtle - often leads to other problems). The signs to watch out for include:-
- Subclinical; Retained cleansing, reduced appetite problems associated with reduced food intake (LDA in particular).Remember cows don’t necessarily have to be recumbent to be suffering from low grade milk fever.
- Clinical; Recumbency, 'S' shaped neck, dry faeces, cold, lack of cudding - eventually death. These are your classical cases. The cow is down and unless treated promptly can progress to death. The longer a cow is down, the more likely she will develop secondary problems such as muscle damage which can make her less likely to recover fully.
Diagnosis is generally based on clinical signs. Blood samples are often taken to analyse later if there has been no improvement – however, blood samples are not much good if taken if supplemental calcium has already been given as this will give confusing results.
Calcium is injected subcutaneously and/or intravenously. A COW NEEDS TO BE GIVEN BETWEEN 6-12G CALCIUM TO TREAT THE CONDITION. A 40% bottle of calcium contains 12g and a 20% bottle of calcium contains 6g. It is important that you are aware of how much calcium is in the bottles that you have on your farm. If in doubt ask your vet.
Take care not to overdose as this can cause heart failure. Always give intravenous calcium slowly and monitor the cow carefully and stop injecting if you have any concerns. The cow will tremble and may begin cudding if treatment is successful. Not all cows will get up straight away.
Be careful when giving multiple bottles of calcium under the skin and into the vein – there is a risk that this may actually raise the blood calcium to too high a level which can cause death in some cases. Giving magnesium under the skin (never directly into the vein) and a phosphorus injections can also help in some cases. Discuss with your vet the best treatment protocol for you on your farm.
The basic aim when preventing milk fever is to adequately prepare the cow for a the sudden increase in requirement of calcium when she calves and begins to lactate. Some suggestions on how to do this include:-
- Feed a low calcium diet in the transition during the last 3 weeks to encourage the calcium regulation mechanisms to kick start early. Ideally you need to be feeding a diet with less than 100g calcium a day which practically can be difficult to achieve. You are basically trying to trick the cow into believing that she is in a state of low calcium during a relatively safe period for her to be in this state (her calcium demands are low at this stage)
- Using a DCAB diet – This method slightly acidies the rumen which in turn produces an environment which supports optimum calcium absorption from the diet. This is effective but requires careful monitoring. Monitor urine pH to check the effectiveness of the diet. You need to supplement dietary calcium when using DCAB (not restrict it as is normally reccomended with other diets). Discuss with your vet or nutritionist if you are thinking about trying a DCAB diet.
- Check the magnesium status of your dry cows and supplement them if necessary – However, don’t over supplement as this can inhibit calcium absorption.
- Monitoring of the cows with blood samples during the dry period will help highlight some potential problems.
Milk fever problems can be a tricky to resolve and often requires dietary changes that can take weeks to show results (you just have to grin and bear it in the meantime). It is better to prevent a problem if at all possible.