7 February 1997

Listeriosis and silage risks

FLOCKMASTERS are being warned not to feed spoiled silage to sheep to safeguard the flock against listeriosis.

Vet David Henderson from the Moredun Foundation, Edinburgh, says the disease affects the ewes brain and causes nervous symptoms and abortion close to lambing. "She may hang back from the flock at feeding with her head drooped or on one side and could appear to be blind," he says.

High levels of the infection can occur in patches of spoiled silage even when clamps or bags of silage are generally of good quality.

Any silage made under poor conditions is particularly vulnerable to contamination. "The bug multiplies in patches where poor fermentation has occurred through soil contamination or, for example, where plastic has been ripped."

He advises flockmasters to avoid feeding spoiled silage by removing all of the affected silage plus several inches of silage surrounding the spoiled patch.

"Treating infected ewes using antibiotics is only effective if the disease is caught in its early stages.

"Any ewes that you suspect are infected must be examined by a vet because the symptoms are similar to some metabolic disorders that occur close to lambing.

"Dead ewes and aborted foetuses must also be sent for post mortems where the disease is likely to have been the cause," he says.