26 April 1996

Extra magnesium is best

way to beat the staggers

By Jessica Buss and Rebecca Austin

GRASS staggers risks could increase after the recent rain, according to Hampshire vet Jonathan Harwood of the St Peters Veterinary Group.

"Grass that has been held back due to lack of moisture will take off," he says. This fast growing, young grass has a low magnesium level, because it has no time to take it up from the soil, he explains. Cold, wet weather increases risks for feed and water intakes of dairy and suckler cows will be low. And reducing mineralised concentrates on offer can also trigger staggers, he warns.

"Cows are unable to store magnesium so need to take in their daily requirement by mouth. Any excess is excreted in the urine."

The best way to supply magnesium is in drinking water troughs. Add before turn-out and for an extended period.

"Magnesium chloride crystals can be added to water by hand at a rate of 40g a cow a day," he says.

For best results add magnesium crystals to the water more than once a day and to all troughs to ensure all cows receive it.

Because cows find magnesium unpalatable for ad-lib feeding it is best supplied in molasses. However, this method is expensive, warns Mr Harwood. And when magnesium is offered in feed blocks cows may miss them.

One study showed up to 20% of cows ignored feed blocks. This is a concern with suckler cows who are prone to stress, which also increases the risks of staggers, he says.

Suspect deaths of cows should be tested to identify possible magnesium shortfalls and to identify how supplementation has failed.

In ewes, staggers is most apparent three weeks post-lambing and is still a danger after six weeks.

ADAS senior livestock consultant Dr Elwyn Rees recommends producers feed 8g a ewe a day of calcined magnesite a week prior to grazing. The mineral can only be retained in the body for 48 hours so further supplementation may be necessary when grass is growing rapidly, he says.

Calcined magnesite is not very palatable so mixing it with molasses allows ewes receiving no concentrates to maintain adequate magnesium levels, says Dr Rees. If available, magnesium-enriched beet pulp is another option.

Adding the mineral to water as soluble magnesium chloride is not always successful. "In wet, cold weather sheep are less likely to drink. Under these conditions they will be most likely to develop staggers." &#42