LISTERIA in the feed has been confirmed as a dangerous hygiene problem on fattening pigs farms.
A study by the University of Veterinary Medicine Vienna followed an incident of fatal listeriosis in fattening pigs in a farm in lower Austria with a 450-pig fattening operation.
Clinical symptoms such as anorexia, bloody diarrhoea and an increased body temperature up to 40° C were observed in about 10 per cent of the pigs, mostly in well-fed animals with a bodyweight of 40-100 kg.
In total, 35 fattening pigs died in about three weeks.
The Austrian researchers used DNA fingerprinting to show the bacterium Listeria monocytogenes was the cause.
They say it should be added to the list of diagnoses when fattening pigs suffer from bloody diarrhoea and septicaemia – especially if silage is part of feeding.
The researchers used two fattening pigs with clinical symptoms and maize silage samples for their study and DNA testing confirmed identical L. monocytogenes strains in samples taken from the pigs and the silage.
A high content of deoxynivalenol – a mycotoxin with potentially negative effects for the immune system – was also found in the maize silage.
The researchers say their results show that L. monocytogenes can cause clinical disease in fattening pigs, the result of immunosuppression due to high deoxynivalenol exposure.
“The feeding of maize silage contaminated by listeria, which survive under poor ensilaging conditions, was the most likely source of infection of the fattening pigs,” says researcher Heiko Stein.
“When feeding silage, it is important that all ensilaging procedures occur under appropriate anaerobic conditions to guarantee suppression of listerial growth.”
L. monocytogenes contamination of pork products is of great concern for public health.