15 September 1995

LOW FORAGE RAISES RISK

Low forage, high concentrate diets put high yielding dairy heifers at increased risk from laminitis, often with severe consequences. Jessica Buss details the latest findings

HIGH-yielding dairy heifers offered low-forage diets risk acute laminitis.

The caution comes from researchers at Liverpool Univer-sity, Veterinary Field Station. Lack of forage causes acidosis which, they say, triggers laminitis.

They advise heifers are introduced on to an adult cattle diet gradually to ensure adequate fibre intakes. This is especially true at housing, when the risk of laminitis is increased.

Liverpool Universitys Dr Bob Ward claims the increase in low-fibre, high-quality silage and high cereal diets can cause acidosis.

"Laminitis incidence was less common after quotas came in because more by-products were fed which are more fibrous than cereals," he says.

As well as including more fibre in the diet to reduce risk of laminitis, Dr Ward recommends housing heifers in straw yards because cubicles and concrete put extra stress on their feet.

John Hughes, Liverpool University researcher and independent dairy consultant, claims to have seen laminitis cases in heifers and second-lactation cows in 9000-litre herds last autumn. "Some of these animals had to be culled," he says.

He warns that stock suffering from laminitis will be sore on all four feet, so it may be difficult to pick them out, for they stand for long periods without moving.

"The only real answer is to get the heifers on straw bedding and watch the diet," he says. "Hay is useful, for it helps keep the rumen stable." &#42

NOT ENOUGH FIBRE – TOO MANY TOXINS

Lack of fibre in the diet reduces rumen pH, causing acidosis. The toxins produced are absorbed through the rumen wall into the bloodstream. These toxins increase blood pressure which causes the laminae of the foot to swell. Because the laminae is trapped between bone and horn it is painful.

The laminae degenerates and damage is permanent.

As the disease originates from the bloodstream, all four feet are affected.

&#8226 Source: Dr Richard Murray, University of Liverpool.

Independent dairy consultant John Hughes: Beware – stock with laminitis will be sore on all feet.

To avoid risk of laminitis, introduce heifers to the adult diet gradually to ensure sufficient fibre intakes.