Strategies to ensure feed safety

In this third and final article, we will look at different tools to mitigate the risks of biological contamination and its consequent impact on production and economics.

Feed and raw materials intended for animal consumption can sometimes be vectors for contamination by pathogenic microorganisms that can be detrimental to pig health, welfare, and performance. The main pathogenic microorganisms that contaminate compound feed are Salmonella spp. (Table 1), Clostridium spp., and Escherichia coli. These represent a risk not just for the animals but also for the workers on farms and in meat processing plants as well as for consumers of meat products (Mariotti et al., 2022).

Other microorganisms with a major impact on swine production have entered production establishments through feed and/or raw materials. As cited by Songkasupa et al. (2022) the introduction of porcine epidemic diarrhea virus (PEDV) in North America in 2013 and 2014 occurred due to contamination of animal feed. Since then, feed biosecurity has become very important to minimize the risk of transboundary animal diseases.

Historically, animal feed mills, unlike other food industries, are not designed to facilitate the cleaning and disinfection process of facilities and equipment. To counteract these difficulties, it is essential to rely on Good Manufacturing Practices (GMP) and Hazard Analysis and Critical Control Point (HACCP) tools, pest management, and collaborators committed to a culture of feed safety.

Table 1. Frequency of positive samples for Salmonella serovars in feed mills.

Source: Pellegrini et al, 2015.

The main tools for controlling pathogenic microorganisms in feed should focus primarily on preventing contamination from entering the facility, reducing microbial multiplication within the plant, and eliminating potential pathogens in feed by physical or chemical treatments.

Physical treatment

Feed processing includes grinding, mixing, and, in some cases, heat and pressure treatments such as extruding, expanding, and pelleting. According to Davies & Wales (2013), these processes can substantially lower the microbial load of feed (Table 2).

Table 2. Microbiological contamination of untreated and heat-treated feed.

Source: CESFAC, 2007.

However, when thermal processes are used, it is essential to consider several control points to minimize the risk of feed becoming re-contaminated (Table 3).

Table 3. Control points to minimize risks of re-contamination after heat treatments.

Source: Klein, 2020.

Another important point for feed safety is pest control. We can use tools such as UV light insect traps, mechanical traps for rodents, ultrasound, electric barriers, etc., which are helpful to avoid chemical insecticides.

Chemical treatment

One widely used strategy for sanitizing swine feed is using organic acids. The most common are formic, propionic, and lactic acid (Table 4). Non-dissociated organic acids can cross the cell membrane of bacteria (mainly gram-negative) and dissociate in the cytoplasmic interior, altering the internal pH and thus their metabolic functions, ultimately causing their death.

Table 4. Minimum inhibitory concentrations of different acids against different bacteria.

Source: CESFAC, 2007.

These compounds can be applied at the feed mill entrance by nebulizing the raw materials. The objective is to treat the raw material before it is stored and used; this type of application is of interest when volatile products are used. Another point of application can be directly in the mixer, the important thing is to ensure they do not fall directly on the vitamin-mineral premixes as they can be detrimental to their stability. Finally, there is the post-pellet application; this is the most critical of all as it can affect feed palatability.

To control mycotoxins, mycotoxin binder products can be used. Additionally, products that improve intestinal health such as prebiotics and probiotics can be used, as well as liver protectors, since detoxifying the organism is mainly done by the liver.

New alternatives

Population growth is increasing the consumption of meat products worldwide. According to FAO, world meat consumption will increase by 14% by 2030. At the same time, in countries where the use of antimicrobials as growth promoters is not yet prohibited, there is growing pressure from both public bodies and consumers due to the possible antibiotic resistance that their use can cause. Therefore, there is a need to look for new alternatives to mitigate the biological risk of feed contamination and consequently improve animal health.

One possible alternative could be the use of natural antimicrobials from plant sources (Table 5), such as some essential oils and phenolic compounds that have shown promising results in the control of both gram-negative and gram-positive pathogenic microorganisms, (Vallejo et al., 2020; Giuliani et al., 2021; Ponce et al., 2022). In addition, these substances have demonstrated significant antioxidant and antifungal effects (Nehme et al., 2021).

Table 5. Antimicrobial properties of some essential oils (+: possesses antimicrobial effect).

Source: Mucha et al. (2021).

Therefore, they are not only a possible alternative for direct use in animals, but also in the preservation of feed and raw materials, consequently increasing their shelf life and reducing the biological risk of contamination of animals with pathogenic microorganisms.

Conclusion

The impact of pig feed safety affects not only animal health, welfare, and productivity, but also the entire food chain and public health. It is our responsibility to guarantee safe feed and we must use all the tools available to do this.