Less Salmonella or stress with plant extracts
The five-seeded plume poppy is a plant native to China and Japan and it’s also the origin of isoquinoline alkaloids. These biologically active elements are now associated with benefits during pig transports, including a lower Salmonella shedding, less contamination and lower stress levels.
Modern intensive swine production systems are characterised by exposing the pigs to several stressors, including transportation, to which the animals must be able to adapt and respond. Transportation of food animals is a routine and necessary practice within the production chain. Additionally, in times of increasing concerns about food safety and long debates on animal welfare, transportation to the slaughterhouse is a hot topic in food animal production.
Transportation has been recognised as one of the most stressful events for pigs because it combines several stressors such as loading, transport and unloading the pigs to a different environment within a short period of time.
Stress response and its consequences
Besides the increase in the serum levels of catecholamines and glucocorticoids, other physiological responses to transportation stress include a significant weight gain reduction, and hyperglycaemia to supply the body with the necessary fuel to respond to the stressor.
In addition, behavioural changes have been observed. Stress is known to negatively affect the gastrointestinal tract’s normal function by inhibiting the gastric emptying, decreasing gastric acid production, and increasing the intestinal motility and permeability. Consequently, intestinal bacterial populations are disturbed and pathogens, such as Salmonella are more likely to survive, colonise and invade the intestinal tract.
Moreover, stress due to transportation has been shown to increase Salmonella shedding and reactivate subclinical infections, hence increasing the food safety risk. Generally, it is accepted that stress negatively affects the immune system, increasing susceptibility to infection. Stress is definitely inflammatory, mainly by activating the NF-κB transcription factor that leads to the release of pro-inflammatory cytokines and oxidative stress. Inflammation causes damage to the intestinal barrier function, increasing the permeability of the intestine to bacteria and toxins.
The response to stress differs between animals due to intrinsic (e.g. genetics) and extrinsic factors (e.g. severity). Particularly, a positive interaction between cortisol levels and fatness within and between different genetic lines has been described. Further, the link between genetics, stress and the quality of the carcass is well known. Additionally, transportation stress can also have a negative impact on fertility, leading in many cases to the impairment of reproduction.
Finally, stress due to transportation has a negative impact on the production and reproduction of pigs, which leads to a poor performance and ultimately, a lower profitability and increased economic losses.
Stress and novel feed additive research
Stress-reducing feeding strategies have been explored and demonstrated to be effective in regulating stress response. However, their effects on Salmonella shedding and the safety of food products have not been investigated. On-farm control of bacterial foodborne pathogens remains a challenge for the swine industry and more research is imperative for optimising the implementation of effective alternatives to in-feed antimicrobials, which would improve animal and public health.
Isoquinoline alkaloids and stress regulation
Herbal extracts from Macleaya cordata have been extensively investigated. The isoquinoline alkaloids (IQ), including benzophenanthridine (QBA) and protopine (PA) alkaloids are the biologically active components of these plants. This group of IQ have been extensively used in North America, Europe and China due to their widespread physiological properties including anti-inflammatory and antibacterial effects.
Research studies have shown that animals fed IQ had improved feed intake and performance. IQs have potential to regulate intestinal inflammation, thus supporting an improved intestinal barrier function and ameliorating the negative impact of stress. Several in vitro and in vivo studies have investigated the anti-inflammatory effect of IQ. Positive acute phase proteins and other parameters of inflammation, have shown to be attenuated by the addition of IQ in the feed of food animals and also by a direct effect in in vitro assays. In addition, a reduced damage to the intestinal mucosa and milder lesions in broilers and pigs challenged with C. perfringens and Salmonella enterica, respectively, were observed when IQ were included in the diet.
Effect of IQ on stress response
The effect of IQ supplementation on stress response has also been investigated, using cortisol as the stress marker. In 2015, a team around the researcher Dr Pongthorn Suwannathada, Khon Kaen University, Thailand, showed that the concentrations of cortisol in blood and saliva, as well as the levels of C reactive protein, were significantly lower in sows receiving IQ as compared to non-supplemented sows. Additionally, fertility parameters, overall health and litter performance were improved.
IQ supplementation was also evaluated in finishing pigs under transportation-stress conditions and the potential benefits on food safety were assessed in a research study at The Ohio State University, USA. Results showed a significant positive correlation between salivary cortisol and Salmonella shedding after transportation to the slaughterhouse in all groups (Figure 1), confirming one more time that stress increases Salmonella shedding. Moreover, only the control group (non-supplemented) showed a significant increase in salivary cortisol after transportation, whereas the levels within pigs receiving IQ (Sangrovit, Phytobiotics) remained close to the pre-transport levels and did not increase significantly. These findings indicated that the addition of IQ was effective in regulating stress due to transportation (Figure 2). In addition, only non-supplemented pigs showed a significant increase in Salmonella shedding after transportation, whereas pigs receiving IQ exhibited a significant decrease in Salmonella shedding as compared to pre-transport levels. Furthermore, carcasses from the control group were significantly more contaminated with Salmonella than carcasses from the IQ-supplemented group (Figure 3). These results suggested that regulating stress response due to transportation by adding IQ to the feed and the water of finishing pigs might be a good strategy to reduce Salmonella shedding and improve the safety of food products.
Conclusion
Besides the well-known benefits of IQ supplementation on animal performance, it may be a novel alternative strategy to decrease the shedding of Salmonella in pigs after transportation to the slaughterhouse, decrease the risk of carcass contamination and improve the negative impact of stress without the risk of promoting antimicrobial resistance.
References available on request.
** The authors can be reached by e-mail at J.Schmitt@phytobiotics.com and V.Artuso@phytobiotics.com respectively.
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