7 August 1998

Chance of milk fever is high

MILK fever risks will be high this month if cows are not kept at tight stocking rates on grass, because of continued lush growth.

Hants dairy vet Jonathan Harwood explains that grass is high in calcium, and a high calcium diet pre-calving predisposes the cow to milk fever – calcium deficiency. Cows can produce calcium from their bones, but switch off that mechanism on a high calcium diet, and then cannot react to the huge demand for calcium immediately after calving. Over-fat cows are at higher risk of milk fever, he adds.

"Put all cows on a starvation paddock in the run up to calving, give them magnesium to help control their uptake of calcium, and feed straw or silage rather than grass." Offer magnesium at the same rate needed to avoid staggers at turnout, either in water, sprinkled on forage or in dry cow rolls, advises Mr Harwood.

"Injections are also available for use pre-calving while oral calcium gels can be given as cows calve. But these are more expensive than offering a suitable diet, supplemented with magnesium for milk fever prevention."