Milk Fever in Suckler cows on Machair Land

Hypocalcaemia, also known as milk fever, is typically not an issue in suckler cows, although experience shows that the conditions on the Uists are just right to be an exception to this rule. Grass and whole crop silages grown on the shell sand rich machair soils result in very unusual mineral contents in locally grown forage.

The problem

Milk is rich in calcium, to meet the needs of the calf to grow its skeleton.  The effect on the dam is that she can run low on calcium levels in the blood. This is called hypocalcaemia and typically seen around calving when milk production starts. Usually, there is enough calcium in feed and the dam has plenty of calcium stored in her bones, but the abrupt change to milk production disrupts the fine regulation of calcium levels in the blood.

Hypocalcaemia can affect cattle at any age; however it is more often seen in older and over-conditioned cows. To start with, animals may be mildly ataxic with ear twitching and fine tremors visible over the flanks. Some cows will lose the ability to stand. They stop eating, have a lower body temperature (below 38°C) and often lie in sternal recumbency with their heads tucked into their flanks. Cows that lie flat on their sides present an emergency and need immediate veterinary attention. If left untreated, these animals may die within hours.

There are other reasons why cows around calving cannot stand up, and most of these conditions will require a vet. Taking the rectal temperature will help to decide what the root cause is.

If cows can still stand, oral calcium supplementation will suffice in most cases; in fact, it is the preferred treatment option. Recumbent cows will need an intravenous infusion. Most recumbent cows will rise within two hours. If treated only once, however, relapses do occur.

As mentioned, something that has been observed from forages analysed for minerals on the Uists, is that due to the nature of the shell sand rich machair, it is not reflective of the “typical” advice that is given for preventing milk fever. Due to the unusually high levels of calcium, chloride and sulphur in the forage, the mineral balance pre-calving needs to be treated differently. Hence why it is so important to analyse your forage for minerals to ensure the correct nutritional advice can be given.

Forages have also been shown to be low in magnesium and vitamin D which are important for the calcium absorption in the gut and regulation in the blood. Knowing the mineral content of the forage fed during the dry period is essential to assess what further supplementation they need.

Where handling facilities and/or the placid nature of the cattle allow, prophylactic treatment of known problem cows with oral calcium around calving should be considered.

What can you do?

A diet high in calcium fed throughout pregnancy increases the risk of milk fever.  Therefore, be aware that high calcium forage will predispose cows to milk fever. High potassium in forage is also a risk, especially if over 2%.

Analyse your forage so you can assess the mineral content of the ration fed during the dry period more accurately. Only once you have reliable information on the mineral content can you decide on mineral supplementation and take advice from a nutritionist.

Ensure adequate magnesium intake, especially during the late stages of pregnancy.  During the dry period a total intake of 20-30g of magnesium is recommended. If potassium levels are over 2% then aim for the upper end of this range. Roughly half the magnesium supply will come from forage, so around 15g should be provided by a mineral, e.g. 100g of a mineral containing 15% magnesium or 150g of a mineral containing 10% magnesium.

Ensure adequate Vitamin D in the mineral supplement (minimum 100,000iu/kg).

Maintain an optimal body condition (2.5-3.0) in dry cows to ensure they have sufficient reserves for calving and don’t let them get fat. Take note of cows that go down with milk fever, they are likely to become reoffenders.