The massive financial consequences of a positive salmonella test result have forced producers to reassess their biosecurity measures, including additives that keep feed bug free.


From this January, any routine testing that finds the presence of either S enteritidis or typhimurium will result in the eggs being unable to go for human consumption unless they have been heat-treated to eliminate salmonellas the bacteria.

The financial impact of this restriction on sale of fresh shell eggs from infected flocks is a cause for great concern as for some flocks, it could mean premature culling.

In 2005, 8% of UK flocks were infected with salmonella. Although this is the lowest level of the EU top six producing nations, the National Control Programme has set the UK sector with the task of achieving a 10% reduction in incidence by 2010.

These pressures to reduce salmonella incidence has led Richard Scragg from Nottinghamshire-based Optivite to believe that while huge strides have been made in salmonella control, particularly with the Lion code and vaccination strategies, there is a requirement to take control to the next level.

“Salmonella is a complex problem as it is spread by several main vectors, and poultry producers need to take steps to reduce all possible risks via a comprehensive risk assessment and prevention programme,” says Mr Scragg.

“This will include improving biosecurity and possibly vaccination, but treating feed is another effective control measure.”

According to Mr Scragg, unit biosecurity is absolutely essential as salmonella can be carried by both welcome and unwelcome visitors. He advises producers to restrict visitors to the unit and to insist on a full disinfection programme including the use of a bacterial handwash before anyone enters housing.

Ideally visitors should use disposable biosecurity suits and either disposable overshoes or wellington boots which are kept on the unit.

Unwelcome visitors including birds and rodents are another major source of salmonella spreading infection to feed and litter via the urine and faeces. It is estimated rodents infect eight times as much feed as they consume. Units should make their housing rodent and bird proof and then implement rigorous control programmes.

Unit hygiene should be rigorously maintained with a thorough cleaning and disinfection routine adhered to between each intake of birds.

“It is also important to keep water systems clean as bacteria will thrive on the biofilm that can build up in drinkers and water tanks. The entire drinking system should be flushed and cleaned on a regular basis,” advises Mr Scragg.

Heat treatment

Animal feedstuffs are known as a possible route by which salmonella can enter the food chain. Heat treatment can reduce salmonella levels in feed, but it has a major weakness as it does not protect feed from recontamination after the heat treatment process. The coolers that reduce the temperature of feed after it has been heated can be an additional high risk area for contamination.

Heat treatment is also expensive, it can destroy valuable nutrients in the feed and uses a great deal of energy, increasing the carbon footprint of the feed manufacturer and making the feed less environmentally friendly.

And it may not kill all pathogens, particularly clostridia perfringens which can survive even very high temperatures.

Organic acids

Treatment of feed or feed storage areas with organic acids can be an effective control measure, offering advantages at both the manufacturing and storage/feeding stages. Organic acids have a powerful antimicrobial effect and can significantly reduce salmonella infection levels while not presenting antibiotic resistance issues.

“Treating feed with organic acids not only reduces salmonella levels in the feed, but also helps keep feed storage areas and feeding machinery free from infection,” says Mr Scragg. “Adding just 2kg of Salgard to feed as it is blown into the feed bin will help eliminate one of the major vectors by which salmonella can be spread by treating both the feed itself and all the storage bins and the feed delivery system.”

New code of practice

DEFRA and the Food Standards Agency have published a new code of practice for the control of salmonella in animal feeds.

The main purpose of the code is to provide information on best practice, and to help those involved in the manufacture, storage and transport of feeds minimise the risk of salmonella contamination. It brings together in one document, the advice that was previously dispersed in three codes and has been updated after an extensive consultation of stakeholders.

While DEFRA says the code is voluntary, the guidance it contains reflects recent legislative developments including the requirements of the EC Zoonoses Regulation and the EC Feed Hygiene Regulation.