6 October 1995

Milk fever alert…

MILK fever cases have risen sharply as producers delay housing to make use of the autumn flush of grass.

"Grass is growing fast and is young and leafy," says Dr Tony Andrews of the Royal Veterinary College. "This means calcium is more readily available to the cow, increasing the risk of milk fever.

"The problem is exacerbated by low levels of magnesium in the grass combined with autumn applications of nitrogen, which inhibits magnesium uptake by the plant and in the rumen," he says.

At calving there is an immediate three- to fourfold increase in demand for calcium and whether the cow gets milk fever or not will depend on how quickly her body can respond to this demand.

Calcium absorption into the blood must be primed to respond rapidly to prevent milk fever.

Harper Adams nutritionist Liam Sinclair says that to do this the cow should be fed under 50g (3oz) of calcium a day pre-calving to ensure she is already working hard to extract as much calcium from her diet as possible.

Then higher calcium diets can be fed after calving and uptake should be sufficient to prevent the disease.

"For the three weeks up to calving restrict grazing and ensure cows are consuming 5kg to 6kg dry matter of straw a head a day plus 2kg to 3kg concentrates a head a day," says Dr Sinclair.

"Feed mineral supplements with a calcium to phosphorus ratio of 1:1 and high magnesium levels.

"But condition scores should be kept between 2.5 and 3, because when the cow gets too fat problems such as acetonaemia can arise," he says.