Salmonella Transmission | A Journey Through Feed

Feed enables Salmonella transmission from field to farm. How? Salmonella occurs naturally in the environment; it doesn’t spontaneously appear in feed mills or on poultry farms. To control Salmonella transmission in poultry, we must understand how Salmonella transmission occurs and identify controllable elements within the production chain that provide widespread impact.

Feed-source Salmonella control and prevention relies on producers’ understanding risk in their individual facilities and implementing high-impact mitigations. Even at a low prevalence, the frequency at which feed is supplied and consumed increases the risk of Salmonella transmission to poultry operations. If Salmonella is in the feed birds will find and consume it. There are over 2500 serovars of Salmonella, and the same ones isolated in soil, feed and feed ingredients, have also been isolated from processing plants and supermarket products.

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How Does Salmonella Transmission in Feed Occur? 

Salmonella requires energy, moderate temperature and moisture to grow. There are aspects to feed production that facilitate these growing conditions. Salmonella is opportunistic, and even after becoming stressed, it capitalizes on ideal conditions. As a natural occurrent in the environment, there are a couple of ways that feed can become contaminated with Salmonella.

Soil as a Reservoir for Salmonella Transmission

We know that Salmonella occurs naturally in the digestive tracts of humans and animals, but did you also know that it can be found in agricultural soil? Not a surprising fact if you think about it. After all, poultry is not the only food product that causes Salmonella outbreaks; fruits and vegetables, such as salad and sprouts, are often cited as a source of human Salmonellosis outbreaks. In addition, studies have shown that fields fertilized with pig and poultry manure can sustain Salmonella for up to 21 days and 1 year, respectively. One study specifically examined the ability of Salmonella to colonize and persist in agricultural soil under conditions of organic fertilization and via irrigation. It was determined that agricultural soil can indeed be a source of Salmonella. Long story short, farmers fertilize fields, plants absorb nutrients from the soil to grow, and Salmonella colonizes plants through plant interaction with the soil, be it the root in the ground or soil contamination of the leaves.

Salmonella Transmission via Feed and Feed Ingredients

Salmonella incidence in feed and feed ingredients is well documented. A 2022 meta-analysis of nearly 100 different studies examining Salmonella in feed and feed ingredients determined that Salmonella prevalence was two times higher in raw materials than in finished feed and milling equipment. Additional published sources have found that Salmonella incidence in finished feed and feed ingredients ranges from 3.2% to 12.5%.

The feed manufacturing process involves many processes that can further amplify Salmonella transmission through feed. For example, feed ingredients are often ground and mixed into poultry feed formulations, which increases the available surface area of feed for Salmonella contamination and increases the total volume of contaminated material passing through the mill. Feed production also yields the production of dust, which can spread Salmonella throughout the milling process and lead to Salmonella residence within feed mills, which further increases the potential for Salmonella transmission to finished feeds.

Why Is Salmonella Prevention and Control in Feed Essential to Salmonella Control in Poultry?

We all understand on a fundamental level how “germs” spread. Salmonella transmission very much follows this model; it requires a host and a fomite. Feed is a fomite for Salmonella, and it is critical to understand why Salmonella prevention and control in feed and feed ingredients is crucial to Salmonella control in poultry.

Feed Is Central to Poultry Production

It is well known that feed is the most significant in poultry production. Poultry growth and development does not occur in the absence of feed. From the day of hatch until processing, poultry interacts with feed.

Feed Is Widespread

Let’s think about how many things feed touches from field to farm. Ingredients are harvested from a field using farming equipment, loaded into trucks and delivered to mills or processing facilities. From there, ingredients are prepared for use in finished feed using equipment and either included directly into a diet or further transported to another location for inclusion. Feed ingredients touch receiving areas, mixers, coolers, presses, and more within feed mills. Finally, finished feed is delivered to farms where it is loaded into silos and eventually ends its journey in poultry feeders. The integrated nature of poultry production means that feed supplied to farms will likely touch several houses within a farm.

Feed Has a Direct Line to the Gut

Salmonella naturally occurs in gastrointestinal systems, so when Salmonella contaminated feed is supplied to poultry, it can easily colonize the gastrointestinal tract. Unfortunately, once Salmonella reaches the farm bird to bird transmission takes over, and there is little that can be done to exert control.

Feed presents an opportunity for Salmonella control in poultry. Salmonella prevention and control in feed can be an effective strategy so long as feed remains Salmonella-free until the point of consumption. Tools, such as feed sanitizers, can be used in finished feed and feed ingredients at low inclusion rates to control Salmonella effectively and will continue to provide long-lasting protection against feed recontamination.

For more information on feed as a fomite for Salmonella, or to learn more about how feed sanitation can aid your Salmonella prevention and control efforts, contact us.

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