Take care to avoid listeria infections

GIVEN the increase in damaging listeria infections earlier in the year, sheep farmers are being warned to take particular care in their late silage making this season.

Liz Genever, Eblex beef and sheep scientist, says: “Caused by bacteria which thrive in soil, faeces and rotting vegetation and can proliferate at relatively low temperatures, listeriosis typically manifests itself in ewes drooling, with drooping faces or walking in circles as a result of abscesses in the brain. It also causes abortions in pregnant ewes and is known to present a particular risk to pregnant women in contact with newborn lambs.

“Ewe infections are primarily associated with high dry matter silage since its limited fermentation can easily be insufficient to suppress bacterial multiplication. Most cases occur four to six weeks after poorly fermented silage is fed, or where secondary fermentation of previously stable silage is permitted by failure to remove stale forage sufficiently diligently at feeding out.”

Dr Genever says later silage cuts are a particular risk because they tend to have higher dry matters than earlier season crops, making the exclusion of air through consolidation far more difficult. This, combined with the fact they are invariably also lower in sugars, means a good fermentation is much more difficult to achieve. And poor fermentation means pHs insufficiently low to prevent bacteria - generally picked up through soil contamination - multiplying throughout the bale or clamp.

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