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Salmonella Reduction in Pork Production

25 November 2016

Yearly approximately 80 million cases of human Salmonella infections are reported world wide. This makes Salmonella one of the most important zoonosis. There are over 2,400 different serotypes of Salmonella of which the most important in swine are S. Typhimurium, S. Derby and S. Cholera-suis, writes Jessika van Leeuwen.

About 95% of the Salmonella infections are sub-clinical in swine. Clinical infections are manifested by lack of appetite, watery yellow diarrhea, fever and acute mortality. Clinical infections are most often seen in starter/finisher pigs and replacer gilts, but sometimes sows and (weaner) piglets are affected as well.

Risk factors for Salmonella infections

Several factors can contribute to the incidence of Salmonella in swine:

  • Hygiene protocol – non-compliance with strict rules regarding internal/external biosecurity of the farm
  • Insufficient drying time after disinfection of barns
  • Introduction of contaminated animals/human/equipment into the farm
  • No ‘All-in All-out’ system
  • Incidence of other infections like: Ascaris suum, PIA (Lawsonia intracellularis) and Clostridium may favour the conditions for Salmonella.
  • Stress
  • Feed management

High-risk ingredients

The use of some ingredients in the preparation of animal feed poses a risk for Salmonella contamination. Especially soy beans (toasted) /soy meal / hulls, rapeseed meal / hulls, sunflower meal / hulls, fish meal (untreated) and egg shells are high-risk ingredients.

Reducing the incidence of Salmonella infection through feed Management

Even though Salmonella is very resistant to survive in different materials even under difficult circumstances (see Table 1) several measures can be taken to reduce Salmonella infections through feed:

- Particle size is important – coarsely ground meal reduces the risk due to slower passage time in the stomach.
- Pelleting of feed > 80o C reduces the risk
- Other measures consist of acidification of feed (and water) and good disinfection of equipment.

Table 1: Approximate survival of Salmonella in different materials

Reducing Salmonella shedding

The consumption of pork coming from contaminated meat/carcasses contributes to the incidence of human salmonellosis. Pigs carrying Salmonella are the most important contaminants of pork meat in the slaughterhouse.

Salmonella shedding

Stress contributes greatly to the shedding of bacteria. The higher the stress of the animal, the higher the number of bacteria that are excreted. This causes a problem for slaughterhouses, as transport to the slaughterhouse is a very stressful event for most animals. The number of bacteria shed after arrival at the slaughterhouse is therefore elevated and this increases the risk of contaminated carcasses. Most slaughterhouses have therefore a monitoring system in which carcass contaminations are routinely measured.

Sangrovit® supplementation decreases Salmonella shedding in pigs

Numerous studies have shown that supplementation of the feed with Sangrovit® contributes to food safety by reducing carcass contamination with Salmonella (Figure 1). Sangrovit® reduces the shedding of Salmonella through 2 different mechanisms:

Firstly, the anti-inflammatory properties of Sangrovit® improve gut health resulting in a more balanced microbiota (Artuso-Ponte et al., 2014). This reduces the amount of Salmonella shed (Figure 2; Robbins et al., 2013).

Secondly, Sangrovit® supplementation reduces stress, as measured by salivary cortisol levels (Figure 3; Artuso-Ponte, 2014; Suwannathada et al., 2015), which results in reduced shedding of Salmonella for animals supplemented with Sangrovit® (Figure 2; Robbins et al., 2013).

Carcass contamination with Salmonella of Sangrovit supplemented pigs

Figure 1: Carcass contamination with Salmonella of Sangrovit® supplemented pigs (dark green and light green) or non-supplemented control pigs.

Fecal shedding of Salmonella in challenged pigs supplemented with Sangrovit (HISANG, LOW SANG), CTC or non-supplemented control pigs

Figure 2: Fecal shedding of Salmonella in challenged pigs supplemented with Sangrovit® (HISANG, LOW SANG), CTC or non-supplemented control pigs (CONT).

Salivary cortisol levels for pigs supplemented with Sangrovit or control pigs

Figure 3: Salivary cortisol levels for pigs supplemented with Sangrovit® or control pigs.

Take home messages

1. Transportation to the slaughterhouse is a stressful event for pigs which increases Salmonella shedding and the risk of carcass contamination.

2. Sangrovit® supplementation contributes to food safety by decreasing Salmonella shedding through stress reduction and improved intestinal microbiota. Therefore, Sangrovit® supplementation is an effective strategy to reduce carcass contamination in the slaughterhouse.

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