Controlling Salmonella Risk in Feed Manufacture
5 June 2020
Preventative measures taken across the feed chain can reduce the risk of salmonella infection on UK poultry units and help strengthen the industry in the light of increased import pressures.
It was in December 1988 that Edwina Currie caused a major collapse in UK egg sales when she said that ‘most UK eggs were infected with salmonella’, putting an unwelcome and unjustified spotlight firmly on the industry. However, it drew attention to an issue and precipitated a range of actions to improve control measures in UK poultry production.
Salmonella remains a public health concern and in September 2019 the Guardian reported that at least 100 people had been poisoned by British eggs in the last three years.
But perhaps the biggest reason for increased awareness of the issue is the forthcoming trade talks with the US and the controversy surrounding the potential importation of chlorinated chicken from the US.
In recent tests carried out by the US Department of Agriculture’s Food Safety and Inspection Service for the year to 25th January 2020, 12% of plants failed the official standards on salmonella on chicken carcases. Plants fail the standards where more than 10% of tests on fresh chicken are positive for salmonella. It is estimated that salmonella poisoning causes 1.35 million infections and 420 deaths in the US annually.
With the increased awareness, the more the industry can show it is taking all steps to prevent infection with salmonella the better placed it will be.
All poultry farms are required to ensure units are regularly cleaned and disinfected, to adopt rigid pest control and biosecuritry measures and maintain comprehensive records as part of a salmonella prevention programme. They must be seen to be working to prevent problems and ensuring their suppliers are taking all appropriate steps to prevent sources of infection is a key element of this.
Feed is a major input on all poultry units and is a potential vector for salmonella, so the feed manufacturing industry needs to ensure that all steps are taken to minimise infection risks. A wide range of enterobacteria, including salmonella, can be present on raw materials and finished feeds. Many widely used feed ingredients including soya, rape, maize and cereals are prone to salmonella with rapemeal particularly susceptible.
Furthermore, it is estimated that up to 6% of all compound feed is salmonella positive. Infection can be reduced by paying close attention to the compounding process where specific scenarios can cause problems.
The first is feed cooling down which leads to condensation, especially if aspiration is inadequate. The warm, moist conditions are an ideal breeding ground for salmonella.
The other problem area is corners such as on conveyors and at the end if lines. Warm products can stick leading to the production of biofilm acting as a reservoir for infection and infecting all feed as it passes these points.
One proven way to reduce salmonella risks is in feed manufacture is to treat feed and feed ingredients with buffered organic acids, particularly as an alternative to formaldehyde. The buffering makes the acids less corrosive and safer to handle than unbuffered propionic or formic acids which are not meant to be used in the industry anymore.
Fysal Feed from Trouw Nutrition is a blend of organic acids with surfactants to ensure even distribution across feed. It is suitable for use on layer feed, breeder feed and other highly buffered feeds.
All product forms and dosages show a gradual improved reduction after 48 hours. The average cfu reduction was 28% after 24 hours, 63% after 48 hours, 73% after 72 hours with 100% reduction after a week.
Table 1 shows the effectiveness of Fysal liquid with a standard propionic and acetic acid formulation. The trial compared seven different concentrations over 24 and 48 hours, looking at the effectiveness in reducing two different strains of salmonella – S. typhimurium and S. enteritidis.
Two key parameters were recorded. The minimum inhibitory concentration (MIC) is the concentration that inhibits 90% of growth, while the 50% inhibitory concentration (IC50) is the level at which 50% inhibition is seen compared to the control.
Fysal Feed is more effective at inhibiting both types of salmonella and has a longer lasting effect, being more potent after 48 hours. It is also more effective in the control of E. coli.
Fysal Feed is corrosive due to the high potency of the product but is very effectiv Compounders who have full stainless steel mills are in a position to be able to use Fysal Feed. Those who have mild steel at any point would need to look at Fysal Liquid and Econ which are non-corrosive blends.
A combination of Fysal formulations can provide effective control across the manufacturing process. An example programme would see Fysal Feed applied to raw materials with Fysal dry powder applied to existing wet spots in the mill. Fysal Liquid should be used after any heat treatment in the mill to protect feed throughout the process and again as close to the last heated point as possible.
To help develop the most cost-effective salmonella control protocols, Trouw Nutrition can carry out a feed safety audit and provide advice on product application, hygiene and management and formulate the best Salmonella prevention programme specific to individual needs.
The main objective is to analyse the origin of contamination with samples serotyped to track the cause of contamination before an optimal product regime is devised. The audit also involves training staff in preventing econtamination.
Lauren Judd , Feed Additives Products Manager – Preservation