To put this into perspective, the 2018 "European Union One Health Zoonoses Report" examined the results of zoonoses-monitoring activities carried out in 36 European countries. The report was a joint initiative from the European Food Safety Authority (EFSA) and the European Centre for Disease Prevention and Control (ECDC). According to their findings, campylobacteriosis and salmonellosis were the two most commonly reported zoonoses in humans. Additionally, in the same period, nearly one in three foodborne outbreaks were caused by Salmonella in the EU, despite current monitoring and mitigation efforts.
Keeping the above in mind, the importance of holistic food safety measures during production cannot be underestimated. Holistic biosecurity plans should also cover animal feed and ingredients, including zootechnical additives: some of these do not only contribute to production goals in terms of growth performance, but also food safety.
Probiotics, sometimes referred to as "direct-fed microbials" are a good example of such additives. These viable micro-organisms are able to confer health benefits to the host when administered in adquate amounts (FAO/WHO, 2002). Their mode of action is often complex, and usually multifactorial (FAO, 2016) including:
- outcompeting pathogens for nutrients or physical space
- producing beneficial compounds
- increasing the digestion and/or absorption of nutrients
- improving the gut barrier function
- reducing gut inflammation
- interacting with the immune system
However, not every probiotic has an impact on food safety. Only those probiotics that are able to mitigate unwanted bacterial challenges do. A good example of this is Miya-Gold® which contains viable spores of a single probiotic Clostridium butyricum strain. The strain has been reported to mitigate unwanted bacterial challenges, both under research and commercial conditions, highlighting its potential role in an on-farm biosecurity plan (Svejstil et al., 2019).
To explain this further, the characteristics of Miya-Gold® are examined in detail. First of all, the probiotic Clostridium butyricum used is an obligate anaerobe and spore-forming bacteria. A spore is a metabolically inactive form of the vegetative bacterial cell, formed when the environmental conditions are unfavourable to the survival of the bacteria. During this spore-forming process, the bacteria achieves a dormant state and forms multiple protective layers to safeguard its core DNA. As a result, the spore is extremely durable and stable. This brings a distinct advantage in terms of stability, both during feed processing and within the animal itself.
In its spore form, the probiotic can pass through the more hostile environment in the initial stages of the gastrointestinal tract (GIT), without loss of viability. Once the spore reaches the distal GIT, where environmental conditions are more favourable, the spores germinate and yield active, vegetative cells. This is of great importance, as the distal GIT is often indicated as the origin location for numerous bacterial food safety risks - including Salmonella.
Secondly, the vegetative cells of the Clostridium butyricum strain can produce significant amounts of butyric acid, an important short-chain fatty acid (SCFA; Svejstil et al., 2019). As the probiotic is active in the hindgut, the produced butyrate can exert its benefits at the location where it will have the biggest impact. The direct beneficial effects of butyrate are well-known (Bedford and Gong, 2017), but there is also an indirect mitigating effect of the SCFA on Salmonella proliferation.
This has been described by Rivera-Chávez et al. (2016), reporting that the absence of butyrate leads to colonocytes utilizing glucose as the starting molecule in their energy production process. As such, epithelial oxygenation increases, resulting in more oxygen not becoming available in the gut lumen. It is exactly this oxygen that can then be used by Salmonella, resulting in an accelerated proliferation and consequently a threat to production standards. Miya-Gold®'s Clostridium butyricum does reach the hindgut, due to its own intrinsic characteristics, ensuring butyrate availability where it counts most for mitigating Salmonella.
As food safety is often compromised by unwanted bacterial contamination, mitigating this risk during production with tools specifically designed to impact these unwanted bacteria makes sense. Probiotics, supported by the definitions and research above, have been proven to be effective feed additives to achieve exactly this. They can be seen as a way to support food safety on-farm whilst benefiting growth performance as well. As a result, a greater benefit for both producers and consumers alike can be achieved.