Reminder over milk fever risk factors

MEDIA RELEASE
Monday, 9 August 2010

For immediate release

Reminder over milk fever risk factors

DairyNZ is urging dairy farmers to exercise caution when using Palm Kernel Extract [PKE] to feed cows pre-calving because of a potential risk of milk fever as a result of its high phosphorus content.

The message comes as a greater incidence of milk fever is being reported nationwide.

DairyNZ principal scientist Dr John Roche says dairy farmers need to be aware of all the risks.

“This advice doesn’t mean that PKE should not be fed. What it does mean is if you have a milk fever problem and are feeding PKE pre-calving, you need to consider that it may possibly be contributing to the problem,” says John. “Of course if you don’t have a problem, don’t try to fix it,” he says.

The recommendation is that, where possible, farmers feed no more than 3kg PKE per cow in the springer mob in problem herds because of its high phosphorus content.

Milk fever is a metabolic disorder that occurs because of low blood calcium and usually happens before or after calving.

John says there are multiple risk factors for milk fever and PKE is just one of many. They are:

• Genetics – for example, Jersey cows are five times more likely to get milk fever than Holstein-Friesians
• Cows that are too fat or too thin are more susceptible
• Anything that makes a cow sick (mastitis, uterine infections, ketosis) or reduces a cow’s dry matter intake (feed restriction in the colostrum mob) will all increase the risk of milk fever
• A difficult calving.

MILK FEVER AFTER CALVING
“The most important way for preventing milk fever at any time is through supplementing cows with magnesium for the last two weeks before calving. Cows should receive 20g magnesium/cow/day,” says John.

“This is equivalent to about 40g CausMag (magnesium oxide)/cow/day. If dusting on pasture or silage at least double this rate (80g CausMag/cow/ day),” he says.

“Supplementing cows with calcium (ground limestone) during the colostrum period will reduce the risk of post-calving milk fever.”

MILK FEVER BEFORE CALVING
Milk fever before calving is less typical and, therefore, far more difficult to deal with, says John.

“Pre-calving magnesium is still the most important way of preventing milk fever,” he says.

“Springing cows should not graze effluent (or night) paddocks, because of the increased concentrations of potassium and phosphorus in the grass.

“Most people are acutely aware of the effect of potassium on milk fever and so effluent paddocks are avoided with springer cows. However, fewer people are aware of the effect of phosphorus.”

High dietary levels of phosphorus reduce the effectiveness of vitamin D in helping the cow absorb calcium.

John says feeds that are high in phosphorus should be minimised pre-calving.

“This would include silage or hay made from paddocks that get a lot of effluent or by-products like Palm Kernel Extract (PKE), wheat middlings (Broll), and wheat or maize distillers’ grains (DDGs). Although these by-products are relatively good energy supplements and are useful carriers for minerals, where possible, feeding to springer cows should be less than 3 kgDM/cow/day.”

ENDS

ABOUT DAIRYNZ
DairyNZ is the industry good organisation representing New Zealand’s dairy farmers. Funded by a levy on milksolids, our purpose is to secure and enhance the profitability, sustainability and competitiveness of New Zealand dairy farming. We deliver value to farmers through leadership, influencing, investing, partnering with other organisations and through our own strategic capability. Our work includes research and development to create practical on-farm tools, leading on-farm adoption of best practice farming, promoting careers in dairying and advocating for farmers with central and regional government. For more information, visit www.dairynz.co.nz

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