14 April 1995

£10m price of Mg deficiency

HYPOMAGNESAEMIA, better known as grass tetany or staggers, costs UK dairy farmers over £10m a year.

It is caused by a deficiency of magnesium, which is essential for muscle activity. When body levels fall dramatically, stock stagger, fall into spasm and quickly die.

Excessive potash and ammonia, typical in spring grass, suppress magnesium uptake. "Unlike other nutrients, livestock do not have magnesium reserves in their bodies which they can draw on when supplies are low," says Scottish Agricultural College nutritionist Dr Mitch Lewis. It is, therefore, important to supplement the diet with magnesium, he says. He recommends 25g to 30g a day for dairy cows grazing spring grass.

Mole Valley Farmers, the south west farmer co-op, recommends no potash is applied to fields intended for grazing before mid-summer, to prevent luxury uptake.

Similarly, too much potash applied to conservation fields in spring can cause problems when first-cut silage is fed. &#42