Maize for Silage
Technical
Insight 337

LISTERIA IN SILAGE

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WHAT IS LISTERIA?

Listeria moncytogenes is a bacterial organism that lives almost anywhere in soil, pasture, manure piles or silage. Listeria thrives in aerobic (oxygen present) conditions and in plant/soil environments with a pH greater than 5.5. Listeria can grow over a wide range of temperature (4 to 38°C) and drymatter (20 to 75%).

Listeria moncytogenes causes Listeriosis which is a bacterial infection, usually of the brain. It is common in ruminants, pigs, dogs, cats, some wild animals and humans.

LISTERIA IN SILAGE

Listeria is rarely a problem in well preserved silages since low pH (less than 5.5) limits its growth. Listeria can be a problem in poorly preserved (pH>5.5) silage stacks or in parts of silage stacks that have been exposed to the air and allowed to secondary ferment prior to feeding (e.g. poorly sealed edges or tops of stacks). Listeria may also be a problem in baled silage if the consolidation is poor or where the bale wrap has been punctured prior to feed-out. To reduce the risks of Listeria:

  • Follow recommended guidelines for harvest timing and/or crop drymatter.
  • Use a quality Pioneer® brand silage inoculant to assist in attaining a low silage pH.
  • Ensure that the silage is well compacted. Follow recommended chop length guidelines to ensure that all air can be excluded from the bunker, stack or bale.
  • Cover the stack or bunker immediately after harvest. Use a good quality plastic cover, tape all joins and seal the edges to exclude all air.
  • Ensure that bales are well consolidated and that a quality plastic wrap is used with the recommended number of wraps being applied to each bale. Ensure that the bales are handled carefully to minimise the risk of puncture and fix any holes as soon as they develop.
  • Avoid feeding hot and/or composted material from within or around the edges of silage stacks.

SYMPTOMS OF LISTERIOSIS

Sheep and goats are more susceptible to Listeriosis than cattle. The first signs of the disease are fever, depression and loss of appetite. Although not seen in every case, the most notable symptom of the disease is that the animal often walks in circles giving the disease its nickname “circling disease”. Although the dam may show no symptoms of Listeriosis, she may abort. Cattle are most likely to abort in the last two months of their pregnancy. For sheep and goats, abortions often take place at 12 weeks or later. Retained placentas may follow abortions in sheep and cattle. 

References

Coping with Catastrophic Ensiled Forage Losses and Cases Studies. Nutritional Insights Vol. 2 No. 2 Pioneer Hi-Bred International, Inc.

Harvesting and Utilising Silage.  Extension Circular 396, Pennsylvania State University.

Listeriosis. Veterinary Science Information, Cooperative Extension, The Pennsylvania State University.



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Revised: June 2015
Expires: June 2018