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EXPERT TALK: The role of feed in controlling Salmonella in pigs

The European Food Standards Agency (EFSA) estimates that 10% to 20% of human cases of Salmonellosis in the EU can be attributed to the consumption of pig meat and they are now focusing their attentions on reducing this.

Many pigs are Salmonella positive at slaughter, as evidenced in EFSA’s 2008 baseline prevalence data, but at farm level even greater percentages of pigs were found to be Salmonella-positive. Salmonella infections in pigs are largely asymptomatic, with a high proportion of infected pigs becoming carriers and intermittent excretors of Salmonella in their faeces. What is clear is that there is no simple answer and on-farm interventions need to be ‘farm-specific’.
 
Identifying the times when Salmonella-negative pigs are exposed to infection, minimising the duration and the scale of such exposure, maximising individual pigs’ ‘resistance’ to colonisation and wherever possible sourcing Salmonella-free pigs are all important steps to take.
 
Many ‘gut-active’ products claim to improve gut health and improve pigs’ abilities to ‘resist’ infection against gut pathogens like Salmonella. Mannin-oligosaccharides, probiotics and encapsulated organic acids are widely used for their abilities to improve gut health, but perhaps most promising of all, the mono-glycerides of butyric, caprylic and capric acid not only appear to enhance gut defences, but also have direct anti-microbial effects against Salmonella in the gut.
 
The link between feed, farm and food is well recognised. As has been learnt from the poultry industry, once farm premises are ‘clean’, once breeding stock and their progeny are ‘Salmonella-free’ and excellent farm biosecurity is maintained, the most effective way to maintain Salmonella-free status is then to ensure that animals receive ‘Salmonella-free’ feed. When exploring the various options for controlling Salmonella in pig feed it is important to remember that the aim should be to expose the feed-eating pig to as few viable Salmonella organisms as possible and not to rely on that pig’s ability (or otherwise) to protect itself from the Salmonella it consumes.
 
Heating feed, over and above the ‘normal’ temperatures achieved during steam-conditioning and pelleting will produce ‘cleaner’ feed. However, even when using feed hygienisers, finished ‘clean’ feed still has to be cooled, stored and distributed. It is all too easy for Salmonella contamination to occur at these stages. Although organic acids and their salts are used for Salmonella control products in pig feed, there are a number of significant limitations to their effectiveness in-feed. When we look again at the poultry industry, where Salmonella control has largely been a success-story, many breeders make use of on-feed chemical treatments. This way, a long-lasting protection is guaranteed.
 
When we look again at the poultry industry, where Salmonella control has been largely a success-story, many breeders treat feed with formaldehyde-based products – thus ensuring long lasting protection. PP
 

Alan Doyle

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