13 September 2021 – Salmonella in poultry production remains a critical issue for the industry, with both the European Food Safety Authority and the Centers for Disease Control and Prevention in the US fingering poultry meat and eggs as the main sources of its infections in humans. And with total eradication of these bacteria being extremely difficult to achieve, it will remain a major focus for poultry producers for still some time.
Reducing the levels of Salmonella that enter the processing plant from the farm has been key in addressing the problem of human infections. However, because of the various on-farm contamination points, including feed, housing, and vertical and horizontal transmissions amongst birds, this is a complex and multifaceted task. Phileo by Lesaffre believes that its Safmannan® postbiotic solution could play a valuable role in helping to reduce the overall Salmonella load in birds, which, in turn, can help tackle bird-to-bird and environmental contamination on farms. In this Industry Perspectives we speak to Alain Riggi, Global Species Manager for Poultry, Ruth Raspoet, Poultry R&D Manager and Paul Price, North America Poultry Manager, to understand the role that postbiotics can play in Salmonella control and how Safmannan® can help poultry producers put safer chicken and eggs on consumers’ tables.
[Feedinfo] Exactly why is Salmonella contamination more prevalent in the poultry sector? Does the problem lie with the animal’s physiology, the production process, a combination of both, or other factors?
[Alain Riggi] Salmonella is responsible for over 91,000 foodborne illnesses in Europe, and approximately 1 million in the US. Poultry meat and eggs represent almost 50% of the sources of contamination in foodborne illnesses, which means that Salmonella can survive and reach the human digestive system. Furthermore, egg, especially the yolk, is rich in nutrients for bacteria like Salmonella. And with egg consumption increasing around the world, it means that food safety has to be better considered by poultry producers.
[Ruth Raspoet] Salmonella is a zoonotic pathogen that can adapt to a wide variety of hosts and environments. Chickens are usually infected through the oral uptake of Salmonella from the environment or by vertical transmission where neonate chickens, with undeveloped immune systems, become contaminated from infected breeder hens and their eggs. After uptake, Salmonella will use its acid-tolerance response to survive the acidic environment of the stomach. It then enters the intestine and invades the intestinal epithelial cells and macrophages where they can easily survive and multiply. Additionally, Salmonella can survive long periods under various conditions outside its host in waste, water, soil, or dust.
[Paul Price] The production systems often allow for faecal transfer to feed when birds are young. Due to birds being social creatures and living in close proximity, other health challenges such as parasites, viruses, and bacteria can spread through flocks and, in many cases, affect the birds’ intestinal balance and allow Salmonella to colonise and move through leaky intestinal barriers.
[Feedinfo] What has been some of the industry’s approaches to tackling the situation thus far? And how successful have they been?
[Alain Riggi] In general, there are three sources of Salmonella contamination on farms:
Current mitigation actions taken by poultry producers can be summarised into five principles based on biosecurity:
- Producing Salmonella-free day-old chicks, e.g., breeder farms sampling and stamping out positive cases, sanitary procedures in the hatcheries, etc…
- Rearing chicks in a Salmonella-free environment, e.g., through cleaning, and disinfecting procedures
- Supplying birds with Salmonella-free water and feed, e.g., using chlorinated water, organic acids and heat-treated feed
- Protecting birds against fortuitous colonisation, e.g., using sanitary lock
- Regularly monitoring the total production chain regularly, e.g., sampling and analysis
With all these measures, the industry manages to reduce the presence of Salmonella in poultry farms. However, according to a report published by the European Food Safety Authority in 2019, the success of these actions is relative, with 2.72% of layer flocks remaining contaminated. The US Food and Drug Administration (FDA) estimates that 79,000 cases of foodborne illness and 30 deaths each year are caused by eating eggs contaminated with Salmonella.
[Paul Price] In US processing plants, companies are regularly implementing antimicrobial interventions during various stages of processing the birds. These interventions can include focuses on pH, surface contact, temperature, and other factors to make a cumulative Salmonella reduction in meat.
However, birds with an exceptionally high Salmonella load, or at a level higher than what cumulative interventions can reduce, can contaminate equipment throughout the processing plant. Further upstream, breeder flocks are often targeted with vaccination and biosecurity measures to prevent Salmonella from getting a foothold in an organisation. There is some evidence of these approaches being effective, but in many cases broiler and turkey flocks are colonised at the grow-out stage due to the ability of Salmonella to transfer on a variety of vectors and fomites. Vaccination is an option here as well, although it is relatively serovar specific and not always completely effective. Plus, if the US’s history with Salmonella in poultry has shown us anything, it is that getting rid of one serovar will result in another one taking over its spot.
[Feedinfo] So with all the preventive measures mentioned being employed to control Salmonella, where do postbiotics fit in?
[Alain Riggi] According to the International Scientific Association of Probiotics and Prebiotics, a postbiotic is a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host”. Our postbiotic solution, Safmannan, is a selected yeast fraction obtained from advanced fermentation of proprietary Saccharomyces cerevisiae strain that is rich in mannan-oligosaccharides and beta-glucans (1.3 and 1.6).
Following years of research and a battery of in-vitro, in-vivo and field trials, we have been able to confirm Safmannan’s effectiveness in reducing the cecal load of Salmonella in birds (more than 1 log reduction), and consequently, shedding in the environment.
[Ruth Raspoet] The beta-glucans in Safmannan will modulate the bird’s immune system while the mannans enable the adherence with type-1 fimbriae found on many pathogenic bacteria, including Salmonella, making it more difficult for them to colonise the intestinal epithelium. Safmannan improves the gut physiology by influencing mucus production, tight junction expression and gut morphology, resulting in reduced translocation of pathogenic bacteria. Finally, Safmannan increases the diversity of the microbiota promoting the persistence of beneficial bacteria while creating an unfavourable environment for potential pathogens like Salmonella.
[Feedinfo] As mentioned, there are various ways in which Salmonella transmission can occur. Exactly how effective is Safmannan at curbing these types of transmissions and where does it have the most impact on Salmonella management?
[Alain Riggi] We have conducted trials in broilers, breeders and layers to evaluate the impact of Safmannan on Salmonella control: first in preventing Salmonella contaminations on farms and, secondly, in reducing Salmonella pressure if contamination has occurred.
A trial published by Zhou et al., in Poultry Science in 2019, demonstrated that Safmannan reduces the population of S. Pullorum and S. Gallinarum that cause pullorosis and fowl typhoid diseases in breeders, improves gut health and, therefore, reduces the probability of Salmonella colonising the ovary grape.
Safmannan has also been demonstrated to significantly reduce the level of S. Typhimurium in the ceca by more than 1 log in laying hens. Reduction in the ceca will lessen the overall load in the environment, leading to a reduced risk of eggshell contamination and transmission of foodborne illness.
It is also essential to reduce the level of Salmonella that enters the processing plant from the farm. The lower the pathogen load is upon entry, the easier it is to bring a safe and wholesome product to market. A trial done on broilers challenged with S. Heidelberg showed that Safmannan helped reduce cecal load by 1 log, making it a proven solution to contribute to the food safety early in the food production chain.
[Paul Price] Research in the US, along with peer reviewed published studies, has showed consistent reduction of S. Enteritidis in commercial layers. This is the top serovar of concern to US regulatory agencies (FDA) related to human health. Reduction effects observed range anywhere from 1 log to 2 logs.
In commercial broiler flocks, large scale monitoring has been completed on broiler ceca and carcass rinses in over 10 different US production facilities. This monitoring revealed a reduction effect in Safmannan-treated birds of anywhere from 1 log to 5 logs and effective against all seven serovars encountered.
[Feedinfo] We’ve discussed that vaccination is still a key tool for many producers to fight Salmonella contamination within breeder and broiler operations. Why do you think they should also consider incorporating Safmannan into their management programmes?
[Ruth Raspoet] Although vaccination has reduced the Salmonella prevalence on poultry farms, additional control measures must be taken to further improve food safety. This is mainly because cross-reactivity of vaccines to other serovars is not always guaranteed. Vaccination within broiler flocks, which have a short life span and therefore immature immune systems, might be less effective in comparison with those of layers and breeders. The extra incorporation of Safmannan into the Salmonella management programme could lead to a reinforced epithelial barrier with a decrease in Salmonella translocation to the systemic organs, an increased activation of the immune system and a further reduction of the Salmonella infection pressure on farm through the binding of the bacteria.
[Paul Price] Vaccination is indeed a needed key for addressing this pathogen, although, as previously mentioned, it can often be limited to a few select serotypes, or can be difficult to implement consistently and effectively at the broiler stage. Safmannan supplementation is extremely stable in feed and provides a continuous fortification to the birds’ immune system, helping to provide a more effective vaccination response.
[Feedinfo] A suggested longer-term solution to the Salmonella contamination problem is to eliminate the serovars all together that are most associated with human foodborne illnesses. Where are we currently on this front?
[Alain Riggi] To achieve long-term success in reducing Salmonella contamination in poultry meat and products, the risk of both vertical and horizontal transmission needs to be lowered. It is also essential to prevent the re-contamination of birds by different Salmonella serovars. Therefore, a myriad of interventions needs to be used, mostly in combination, to reduce contamination at preharvest stage. Furthermore, control programmes are enforced by some of the world’s largest poultry producers, like the US, the EU and Brazil. For instance, as a result of the EU’s control programmes for poultry flocks, the number of cases of humans infected with S. Enteritidis have dropped by 60%.
[Paul Price] In terms of eliminating these serovars, this can be targeted with vaccination in many cases, and some companies undertaking eradication programmes for breeder flocks that are found to be positive for the serovars of concern. A lot more focus has been placed on research with products to combat the top disease-causing serovars. Naturally all Salmonella control requires a multitude of steps, all working in tandem to reduce the issue.
Published in association with Phileo by Lesaffre