Minimising milk fever

Magnesium supplementation is by far our most important tool to reduce milk fever in our herds.

DCAD, MgS & MgCl

There is still debate whether the DCAD principle of milk fever control works in New Zealand. The great thing we have learnt from using DCAD is just how effective magnesium sulphate (MgS) and magnesium chloride (MgCl) can be in preventing milk fever when used in support of the traditional control programs that use magnesium oxide (MgO).

Unfortunately, both of these salts have their down sides; one of which is that both contain far less elemental magnesium than MgO (10%, 12% and 55% respectively), so we need to use them at higher levels.

MgCl is also very bitter and will put cows off water, while MgS can cause scouring when used in high amounts, so it is important that you work with your vet to develop a program that will maximise the benefits and minimise the side effects of these products.

Recommended magnesium dosages for springing and lactating cows

Remember that springers, colostrum mob cows and the milking herd need the correct amount of magnesium everyday, rain or shine.

Avoid potassium

The other key gain in our understanding is the role that potassium (K) plays in milk fever. The level of pasture potassium on a farm has a huge influence on both magnesium uptake by the plant from the soil, and magnesium absorption in the cow.  High nitrogen and high rainfall can also play a part in reducing magnesium absorption, but high K is the real driver.

• Knowing the K levels on paddocks to be grazed by the springer mobs gives a good indication of the risk of milk fever

• Farms with high K levels should supplement magnesium right through winter to maximise weight gain in dry cows and minimise metabolic disease

• Don’t calve down on effluent pastures as effluent contains very high levels of K

• Spring calving farms should avoid putting potash on calving paddocks between March and October

• High rainfall releases K from soils, increasing the level in plants, making this year a prime one for increased milk fever

A few other pointers to good transition management:

• Ensure that cows spend at least three weeks in the springer mob by drafting springing cows early

• Look closely at dry matter intake (not allowances) and transition feeding to allow the rumen to get used to the milking cow diet

• Ensure that cows in the colostrum mob have adequate magnesium everyday and are well fed to avoid ketosis - a risk factor for milk fever and a disease in its own right.  Aim for energy intakes of 90-110 MJME /day depending on cow size  

• Consider supplementing the colostrum mob with limeflour to increase calcium intake. Do not supplement the springer mob with lime flour, unless you have precise advice, as this will trigger milk fever

• We can blood test the first batch of springers to check their mineral status and take pasture samples to establish the degree of risk of milk fever

• If more than 5% of the herd had milk fever last year, take the time to develop a plan with your vet to reduce it this year, and do it now!

Nowadays, with careful prevention it is possible to calve an entire herd with less than 3% needing treatment for milk fever. Contact us for testing and customised advice.