Avoiding Listeria

Listeria spp. are ubiquitous environmental bacteria and are also found in the faeces of normal animals.  They will multiply in silage following entry of air and when pH is ≥ 5.5.  Spoiled silage is traditionally blamed for most outbreaks of listeriosis but in some cases has not always been fed.  A wet winter would leave muddy conditions which could increase disease risk through ingestion of soil.

• Check silage analyses for high pH and/or high ash content (>80g/kg DM) indicating large amounts of soil contamination at harvest e.g. cut very low, molehills or wet weather at harvest.
• Avoid feeding silage that is either obviously spoiled or from punctured bales.  The top layer of the pit and the outer layer of bales are highest risk.
• Clean away uneaten silage before adding more.
• Make silage accessible to sheep avoiding trampling by muddy feet.
• If rolls are fed directly onto the ground change the area where feeding takes place.

Heather Stevenson, heather.stevenson@sac.co.uk