Contaminated silage is being blamed for a recent case of botulism in which a number of dairy cows died in the Shoalhaven.
The South East Local Land Services said the cause of the infection at the commercial dairy had been diagnosed by the NSW Chief Veterinary Officer.
Botulism is a relatively rare condition that crops up from time to time, particularly on dairies and in feedlots, with Local Land Services South Coast manager Paul Lyddiard, saying there was no public health risk from the incident.
Botulism is a paralysing disease caused by a potent nerve toxin produced by the bacteria Clostridium botulinum.
C. botulinum and its spores are widely distributed in the environment in soils, sediments, and in the gastrointestinal tracts of fish and animals.
They can also be absorbed via contaminated feed.
Once the toxin is absorbed it travels via the bloodstream to the nerve endings and blocks the transmission of nerve impulses to muscles resulting in paralysis.
Animals die of respiratory failure from paralysis of the breathing muscles.
Feed contamination can be caused by bodies of small animals such as lizards, snakes, turtles or mice that are inadvertently trapped in grain, hay or silage during the harvesting or storage stage.
“The land manager involved in this local incident has been in constant contact with their vet, industry contacts, Local Land Services and the NSW Department of Primary Industries throughout the event,” Mr Lyddiard said.
Local Land Services vets and NSW DPI worked with a private vet to collect samples and establish a diagnosis, which has been communicated to the relevant government and industry bodies.
Mr Lyddiard said the deceased cattle were removed and disposed of at an approved waste facility, with the advice and assistance provided by the NSW EPA and Shoalhaven City Council.
“Remediation works on the property have been completed to EPA’s standards and satisfaction, with Local Land Services providing support and assistance,” he said.
Mr Lyddiard said the suspected contaminated silage was being composted in line with Australian standards.
The land manager has been offered support and counselling from NSW Health.
What is botulism?
Most cases are due to contamination of the feed or water by rotting organic matter containing the botulism toxin or bacteria.
Bodies of small animals such as lizards, snakes, turtles or mice that are inadvertently trapped in grain, hay or silage during the harvesting or storage stage are some of the common types of rotting organic matter that contaminate feed.
High moisture feeds such as silage or brewer’s grains when allowed to rot rather than ferment can provide an ideal anaerobic environment for botulism growth.
Seven types of toxin have been identified, designated A to G. Vaccination programs are available to minimise risk.
Some of the highest mortalities have occurred where mixing wagons were used in preparing dairy rations and the toxin was evenly distributed throughout the mix.
Once the toxin is absorbed it travels via the bloodstream to the nerve endings and blocks the transmission of nerve impulses to muscles resulting in paralysis.
Botulism causes a progressive paralysis and animals die of respiratory failure from paralysis of the breathing muscles.
Animals are usually found sitting down, unable to rise and their breathing becomes progressively more laboured.
Losses can be seen for up to 17 days after ingestion of a contaminated feed.
Botulism can be confused with hypocalcaemia or milk fever.
