Mycotoxins can alter the intestinal function and immune function of poultry, increasing their susceptibility to infection with pathogenic bacteria, such as Salmonella. The efficacy of vaccines can also be negatively affected. Concentrations of mycotoxins below the EU and US limits, or at concentrations lower than those that would cause overt clinical mycotoxicosis, may still affect the performance and health of birds. This may be due in part to co-contamination: several studies have suggested interactions, which may lead to additive, antagonistic and synergistic effects of multi-mycotoxin exposure.

1. Mycotoxins, an everlasting problem worldwide

Mycotoxins are widespread throughout the world. From the field to the feed, mycotoxin production is a cumulative process, which is induced by several factors, the most important being climatic conditions and agronomic practices during cultivation. However, each mycotoxin has its own pattern of development, so crop contamination can significantly differ each year in each geographical region, both in terms of quantity and mycotoxin type. This means that the mycotoxin risk is constant but dynamic in nature. Figure 1 shows the global occurrence of the agriculturally important mycotoxins.

Figure 1. Global trends of mycotoxins prevalence (adapted from Perrone et al., 2020).

The recent increase in raw material prices, along with availability issues, is pushing formulators to increase the level of inclusion of alternative ingredients such as DDGS or wheat bran. While the use of co-products offers feed cost savings, the unintended consequence is that they are likely to contain higher levels of mycotoxins.

The US Poultry & Egg Association published preliminary results of research showing that including DDGS at 15% in poultry diets may lead to decreased bird performance. When the birds have a mild to moderate Clostridium perfringens challenge, this can lead to more severe cases of necrotic enteritis as well as a decrease in technical performance. The cost of any disease outbreak will further eat into producers’ margin, over and above the effect of the mycotoxins themselves. In wheat bran, mycotoxin concentration is much higher than in the whole grain. A study done by Arvalis in France showed that concentration in wheat bran was 2.4 times higher than in the whole grain.

2. Effect of mycotoxins on bird health and solutions

Gut health and necrotic enteritis

The disease necrotic enteritis was first described in chickens in England in 1961 and has been reported in most countries around the world. Necrotic enteritis has been identified in broilers, laying hens, turkeys, and quail. Necrotic enteritis is caused by toxins produced by Clostridium perfringens. While anything that causes intestinal irritation can lead to necrotic enteritis; stress, intestinal disease (particularly coccidiosis), intestinal parasites (especially round worms), immune suppression by mycotoxins, chicken anemia virus, Gumboro disease or Marek’s disease: have all been specifically linked to the disease.

Following ingestion of mycotoxin-contaminated feed, intestinal epithelial cells can be exposed to toxins. Direct intestinal damage can be exerted by the biological action of mycotoxins. Trichothecenes like deoxynivalenol (DON) or T-2 toxin effect actively dividing cells such as those lining the gastrointestinal tract. The gastrointestinal tract is also sensitive to trichothecene induced apoptosis (cell death), which mainly affect the gastric mucosa, gastric granular epithelium, and intestinal crypt cell epithelium (Bondy and Pestka, 2000). The toxic action of trichothecenes results in extensive necrosis of the oral mucosa and causes gizzard lesions (Leeson et al., 1995). The T-2 toxin inhibits DNA, RNA and protein synthesis, affecting the cell cycle and inducing apoptosis programmed death of cells (Rocha et al., 2005). Antonissen et al. (2014) found that feeding deoxynivalenol contaminated feed with concentrations lower than the maximum EU guidance level of 5 ppm to broilers, is a predisposing factor for the development of necrotic enteritis. After a request from the European Commission, EFSA reassessed the risks of DON in poultry in 2023. They suggested a new reference point for adverse animal health effects of 0.6 ppm, to take into account the impaired production performance and signs of unbalanced gut.

Vaccination failure

It is well known that immunity acquired through vaccination can be impaired by ingestion of mycotoxins. Hegazy et al. (2011) revealed that mycotoxicosis could be the cause of vaccination failure against Avian Influenza virus. Mycotoxins reduce the level of antibodies following both infection and vaccination – reducing the activity of phagocytic cells, which ingest and dispose of bacteria, viruses, and foreign material. This results in decreased resistance to infectious diseases, reactivates chronic infections and decreases vaccine efficacy.

The presence of mycotoxins in poultry rations could therefore lead to a breakdown in vaccinal immunity and consequently increase the occurrence of diseases such as infectious bursal disease virus (IBDV) or Adenovirus.

Figure 2 reports the results of a study designed to quantify the impact of mycotoxin ingestion by broilers to NCD vaccination response. As well as determining the efficacy of Toxy-Nil® Plus (a mycotoxin deactivation product) to mitigate those effects. From the results it can be concluded that the addition of Fusarium mycotoxins (deoxynivalenol and zearalenone) significantly decreased anti-NCD titers compared with control. Supplementation with a mycotoxin deactivation product, to feed without mycotoxins, recovered the NCD-antibodies level observed in the control group. The reduction in anti-NCD titer when mycotoxins were present, was completely offset by the addition of an effective mycotoxin deactivation product to the contaminated feed.

Figure 2 :The effect of Toxy-Nil® Plus on the antibody (NCD) titer in broilers fed a diet naturally contaminated with Fusarium mycotoxins

Values with no common superscripts are significantly different (P<0.05)

Salmonella predisposition

Salmonella are gram-negative bacteria, which are responsible for 1 of the 4 most frequent global causes of diarrheal diseases. Foodborne diseases are a substantial burden on human health, as they affect 1 in 10 people throughout the world every year and cause 33 million deaths. Poultry production is of most concern, through consumption of meat and eggs. A total of 2,400 types of Salmonella, called serovars, have been identified. Some of the most frequently encountered are S. Heidelberg, S. Enteritidis, S. Indiana, S. Kottbus, S. Infantis, S. Montevideo, S. Saintpaul, S. Senftenberg and S. Typhimurium. Salmonella is a zoonosis, which means that it can contaminates both humans and animals (wild and domesticated), which makes the control of its spread complex. The control of Salmonella on farm is key to preventing contamination and infection.

Salmonella colonizes the gut in three different steps. First by adhesion, then by invasion of the epithelium, and finally by infecting the lymphoid tissues. Salmonella impairs gut homeostasis (according to the three pillars: microbiota, mucosal barrier, inflammation state) and uses the host defense mechanisms to its advantage. In fact, inflammation induced by Salmonella leads to growth inhibition of the commensal micro-organisms in the gut. This allows Salmonella to take advantage over other commensal bacteria, multiplying and to colonizing the host gut. Poultry generally have no symptoms, which complicates the diagnosis and increases the risk of sending contaminated birds to the slaughterhouse.

Mycotoxins contamination can create a perfect playground for Salmonella in the gut. Different mycotoxins have the following effects:

Damage gut epithelium (AFLA, DON, FUM)
Increase intestinal inflammation (DON, FUM, AFLA, T-2, OTA)
Alter antioxidant status (DON, FUM, AFLA, T-2, OTA)
Change microbiota profile (DON, AFLA)

Consequently, their presence increases Salmonella invasion, translocation, colonization, clinical signs, and changes to microbiota.

Unike Plus, a mycotoxin deactivator based on mineral clays, deactivated yeast, botanicals, and antioxidants has shown beneficial effects on:

Gut permeability
Salmonella prevalence
Redox status
Inflammation

A trial evaluated the effect of Unike Plus in a co-challenge on mycotoxins and Salmonella Heidelberg. One-day-old Ross broilers were placed in six different experimental groups of 46 broilers each and the trial lasted 28 days. Unike Plus was added to the feed at 1 kg/t and from the first day birds of the determined groups started to receive the Fusarium mycotoxins in the feed (via a fungi culture). On the fourth day, the birds were infected with 10⁸ CFU of Salmonella Heidelberg. Among other analyses, the Salmonella count was measured. Results are presented Figure 3. The mycotoxin deactivator could significatively reduce the Salmonella count compared to the treatment without mycotoxin deactivator.

Figure 3 : Salmonella count (Log MNP/g) in ceca content at d14

Unike Plus can support the health of animals in a preventive strategy against mycotoxin and indirectly against Salmonella infection. It also successfully promoted the intestinal health of broilers challenged with Salmonella and mycotoxins.

Shutting the gate

Mycotoxins may alter birds’ susceptibility to infectious diseases by affecting intestinal health, as well as the innate and adaptive immune systems. Research is discovering more about the effects of mycotoxins on infectious diseases. It is therefore essential that the industry have practical and economical solutions to counteract mycotoxin contamination of feed and its effects on animal health.

Adisseo’s mycotoxin deactivator range offers powerful protection against broad-spectrum mycotoxin contamination. Additionally, Adisseo supports the feed industry by providing mycotoxin risk assessment services (prediction before harvest, harvest bulletin, lab and field analysis, risk assessment); to help identifying the best strategy to adopt.

Product names and availability may vary by region, please contact your local Adisseo representative for more information.