Poultry products are one of the main sources linked to Salmonella in the human food chain, in spite of the fact that the industry implements control strategies throughout production. When humans are infected, the short-term effect of Salmonella is foodborne illness, but the distrust in the food products that led to the illness can be felt long-term. For poultry producers, foodborne illness results in food waste, recalls, lost revenue, and loss of brand reputation. 

What does “Zero Salmonella” mean?

As poultry meat and eggs are two main agricultural goods traded globally, food inspection agencies are implementing stricter policies for Salmonella. The “zero Salmonella” claim is sought after but has caused debate around the world, with just a few programs able to manage a significant, continuous reduction in the food chain. The challenge with reaching “zero Salmonella” is that prevention and monitoring policies must be implemented throughout production, a tedious but necessary task. 

Poultry and Salmonella: a common problem

Salmonella is regularly found in the poultry microbiome. There are over 2,500 variants (serotypes) associated with poultry, with very few causing illness in poultry and more causing illness in humans. Usually, Salmonella contamination starts with a bird consuming contaminated feed, debris, or fecal material (Chadwick, 2017). Salmonella can colonize in multiple locations throughout the poultry gastro-intestinal tract and, if there is damage or stress to the gut, can move into circulation and colonize in other organs (Pulido-Landínez, 2019). It will compete with the native gut microbiota for colonization sites and nutrition sources. Once colonized, it can replicate and move throughout the digestive tract, being found from crop to the ceca. Furthermore, the intestinal lining is shed every few days, so Salmonella is shed in the feces to the rest of the flock. 

Salmonella in the feed and drinking water

Feed comprises 70% of poultry production costs, thus efficient and sustainable utilization of feed ingredients and related resources is paramount to have the lowest possible cost with the least feed material waste. Salmonella contamination risk increases due to ingredients coming from multiple locations and cross contamination in feed can derive from crop harvest, feed processing, transportation, and storage (Chadwick, 2017). Monitoring feed ingredients that tend to be Salmonella carriers, like protein and vegetable sources, can help reduce the risk of contamination. Feedmill equipment must also be regularly cleaned to reduce cross contamination (Pulido-Landínez, 2019).

Feed hygiene in combination with water sanitation practices can help control which bacteria are consumed by the flock. One of the most effective feed hygiene strategies, addition of formaldehyde, can no longer be used in multiple countries due to regulatory restrictions. Chlorination and acidification treatments have been used in water to reduce bacterial populations. Organic acids are typically used for both feed and drinking water, which act by damaging the bacterial cell wall due to their antimicrobial activity, reducing the amount of Salmonella in the feed that can colonize in the bird’s gut (Hajati, 2018). 

Controlling Salmonella in breeding eggs and table eggs

The two contamination points in egg laying birds (laying hens and breeding hens)—the egg contents and the shell—can be controlled by reducing the amount of Salmonella in the hen’s gut.

Internal egg contents become contaminated when Salmonella from the digestive tract move into the bloodstream through damaged intestinal epithelium and colonize the reproductive tract. Once in the reproductive tract, Salmonella is transferred to egg contents through the vitelline membrane (Gast et al, 2005). Salmonella is also shed in the hen’s feces, thus contamination of the eggshell can occur if there is fecal material on the eggs. The porous structure of the eggshell allows for movement of bacteria from feces into the egg, especially if the eggshell is poor quality.

Control points for Salmonella in both types of eggs can be regulated through managing the hen’s gut health and microbiome. If we can reduce gut colonization for internal egg contamination and fecal shedding for external egg contamination, we can drastically reduce the likelihood of eggs carrying Salmonella. 

Controlling Salmonella at the hatchery

Survey studies have shown large variability in Salmonella detection at the hatchery, depending on sanitation practices (Van Der Fels-Klerx et al., 2008, Ren et al, 2016, Ha et al., 2018, Oaster et al., 2022). Even with strict sanitation processes in place, there is still a risk of contamination. Salmonella has been known to increase ‘Exploders’ – the eggs exploding during incubation and hatching due to overgrowth of pathogenic bacteria – resulting in embryonic death. Furthermore, dust, debris, and fecal material released from contaminated eggs during incubation and hatching can lead to spread of contaminates to other chicks (Cason et al., 1994). Since chicks have an unestablished gut microbiota, Salmonella can easily colonization with little competition.

With proper hatchery sanitation practices and the introduction of controlled competitive exclusion, we can reduce the risk of Salmonella in chicks before they go to the farm. 

Controlling Salmonella in commercial broilers

Broilers are most susceptible to Salmonella contamination and colonization in the first two weeks of life as their gut microbiota is naïve and in the process of being established (Fathima et al., 2022). To outcompete Salmonella, the intestine needs consistent and continuous protection through grow-out with tools for competitive exclusion which can deprive Salmonella of places to colonize, as well as reducing the food sources available for Salmonella to colonize and proliferate. By protecting intestinal health and integrity and improving nutrient utilization, less Salmonella can grow and replicate in that environment. This benefits the flock as a whole with less horizontal spread between flock mates. 

A comprehensive multi-pronged solution 

Because of the potential for contamination all along the production process, achieving “zero Salmonella” requires a comprehensive strategy:

• No matter the quality of the raw materials, use feed hygiene and water sanitation strategies that can reduce Salmonella contamination.

• Provide a ‘competitive exclusion’ product, such as a synbiotic (prebiotic and probiotic), as early as possible to help deprive Salmonella of colonization sites and improve intestinal integrity thus, improving nutrient utilization by the bird and limiting access to nutrients Salmonella needs for colonization, proliferation, and translocation to other organs.

• Protect intestinal integrity and microbial balance by providing proper vitamin levels and controlling mycotoxins.

• Know what you are dealing with. dsm-firmenich's microbiome services measure both microbiome taxa composition and functionality which gives further insights into the microbiome, including Salmonella.