Since we are approaching the silage making season, I would like to remind you about the care that needs to be taken with the preparation and cover of pit silage to ensure proper airtightness and compaction of the material that is to be ensiled. This will ensure proper ensilation and a pH drop in the silage, which apart from maintaining the food value also are major factors in suppressing possible growth of listeria and mould. While mould is clearly visible listeria bacteria are not, both organisms are found in the top and at the sides of the stack were compaction and airtightness are most easily compromised. Soil contamination via dirty tractor tyres are also a possible source of listeriosis bacteria to be introduced to the stack.