prevalence of Salmonella infections in pigs, including the health status of the animals and their stress levels. Modern swine production systems typically expose animals to several stressors, including mixing, high stocking density, a poor environment, transportation and weaning. Stress is widely known to negatively affect gut health. Delayed gastric emp- tying, increased intestinal motility, intestinal inflammation and permeability and disrupted microbial population balance in the gut are well-known consequences of stress. Addition- ally, stress has been recognised to increase susceptibility to infections and to reactivate subclinical infections. Furthermore, Salmonella is known to exploit intestinal inflam- mation to cause infection. Therefore, stress and its conse- quences on the gastrointestinal tract can increase the shed- ding of Salmonella in subclinical carriers and increase the possibility of spreading the bacteria to other animals and the environment.
Pre-harvest control is key Controlling foodborne pathogen infections on the farm is not easy, but it has a great impact further down the food chain, as the live animal is the main source of bacteria. Several nutritional strategies have been used in the swine in- dustry to control Salmonella infections, including the use of in-feed antimicrobials. However, their association with the emergence of resistant bacteria, and the increasing public health concern, has promoted the use of non-antimicrobial alternatives.
Compounds that can help public health Isoquinoline alkaloids (IQs) are plant-based compounds, which have been demonstrated to exert anti-inflammatory effects in the gut of food animals, including pigs. In addition, IQs have been shown to inhibit the enzyme amino acid decarboxylase, which is produced by the gut bacteria and is
Figure 1 - Effect of IQs supplementation on salivary cortisol levels before and after transportation.
5 6
1 2 3 4
0 IQS feed Footnote: a, b: p≤0.05 IQS feed & water CON Source: Artuso-Ponte et al., 2015. BEFORE AFTER b
a a a a a
responsible for amino acid degradation. IQs supplementa- tion in pigs has been demonstrated to down-regulate stress response in pigs, for example after transportation to the slaughterhouse (see Figure 1). Moreover, this was correlated to decreased Salmonella shedding, indicating that modu- lating stress could be a good strategy to control Salmonella infections on the farm and the consequent food safety risk. Furthermore, carcasses from IQs-supplemented pigs were sig- nificantly less contaminated with Salmonella, indicating that supplemented animals entering the abattoir had lower Sal- monella loads in their gut (see Figure 2). In addition, another study has shown that supplementing pigs with IQs reduced intestinal permeability and decreased the number of bacteria and the duration of Salmonella shedding. Overall, research findings support the use of IQs in pigs to modulate stress response and its consequences on the intes- tinal barrier, mitigating Salmonella infections and minimising the risk of carcass contamination.
Figure 2 - Salmonella shedding before and after transportation to the slaughterhouse (A); Carcass contamination (B).
BEFORE
100 200 300 400 500 600 700 800 900
0 IQS feed
Footnote: a, b: p≤0.05 Source: Artuso-Ponte et al., 2015.
IQS feed & water CON a AFTER a a b
10 15 20 25 30 35 40
b a
0 5
IQS feed IQS feed & water CON b
a
a
▶ PIG PROGRESS | Volume 37, No. 10, 2021
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Salmonella shedding, CFU/g
Salmonella in carcass, CFU/ml
Salivary cortisol, ng/ml
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