Mycotoxins as Predisposing Factors to Health Challenges

The negative impacts of mycotoxins in poultry can be far-reaching, decreasing gastrointestinal integrity, immunity and performance in broilers, thus resulting in economic losses. Given the high prevalence rates of contamination in poultry feed, a mycotoxin risk management strategy is needed to reduce the challenges in poultry production and ensure profitability.

Poultry producers frequently ask: What is the real impact of mycotoxins on the bird’s productivity? What sounds like an easy question is, in the case of mycotoxins, unfortunately not so easy to answer. A key consideration to evaluate the impact of mycotoxins includes mycotoxins as potential predisposing factors to health challenges.

A lack of visible clinical signs is primarily due to the short life cycle of broilers. This means that the challenge may lurk within the animal but not have time to manifest outwardly. The combined effects of more than one mycotoxin make the diagnosis more difficult. However, the major impacts of mycotoxins on poultry health have been clearly proven: destruction of the villus of the intestines which harms nutrient absorption and digestion while increasing leaky gut and modulation of the local immune response and microbiota which increases the opportunity for vaccine failure and dysbiosis.

• Decreased nutrient absorption: Mycotoxins, especially deoxynivalenol (DON) and fumonisins (FUM), affect several aspects of intestinal integrity. A meta-analysis (Grenier and Applegate, 2013) showed a clear influence of DON and FUM (Figure 1). Mycotoxins reduce the functionality of tight-junctions between the intestinal cells, opening up the opportunity for pathogens and antinutritional factors to move from the intestinal barrier to the bloodstream. This challenges the immune system and liver, redirecting nutrients and energy away from growth. The liver is directly affected by most mycotoxins. In broilers, a visible fatty degeneration and an increase of approximately 15% in liver weight were reported. This reflects an increased cost of nutrients and amino acids, especially methionine which is the first limiting amino acid for broilers. A strategy that directly deactivates mycotoxins is the greatest opportunity to prevent the nutritional losses without having to manage nutritional changes in the diet.

Figure 1. The effect of DON, NIV, FB1, T-2 toxin and ZEN on the intestinal epithelium. They alter the different intestinal defense mechanisms including epithelial integrity, cell proliferation, mucus layer, immunoglobulins (Ig), and cytokine production. (Source: Antonissen et al., 2014)

• Vaccination failure: Modulation of immune response is one of the main modes of action of mycotoxins which can impact how birds respond to disease challenges and vaccination practices. Mycotoxins act as a predisposing factor to reduce the immunity for viral diseases in broilers (Kamalavenkatesh et al., 2005; Hanif and Muhammad, 2015 and Yunus et al., 2012). Ochratoxin, DON, T2, cyclopiazonic acid significantly reduced the antibody titer for Newcastle disease virus (NDV), infectious bronchitis virus (IBV), infectious bursal disease virus (IBDV), and hydropericardium syndrome (HPS). It increases the susceptibility of birds to infectious diseases that could be avoided under normal conditions.

• Predisposition for Coccidiosis and Necrotic Enteritis (NE): Antonissen et al. (2014) evidenced that low to moderate doses of different Fusarium mycotoxins (DON, NIV, FB1, T-2, ZEN) predisposed birds to a more severe response to a coccidiosis and NE challenge as shown with reduced immune response and efficacy of the anticoccidial treatment. Additionally, FB1 and DON contamination resulted in a more severe NE challenge in separate studies (Antonissen et al., 2012 and Antonissen et al., 2015). Coccidiosis is one of the most costly diseases in poultry production. By monitoring and reducing mycotoxins, coccidiosis management strategies can be more effective.

• Food safety contamination: Evidence of a higher susceptibility to Salmonella typhimurium and Campylobacter jejuni were also reported in the presence trichothecenes (DON and T2), suggesting that these compounds may modulate the bacterial metabolism (Vandenbroucke et al., 2011; Rahnu et al., 2020). As previously described, mycotoxins result in a ‘leaky gut’. Once the junctions between intestinal cells are disrupted, an exchange of molecules happens between the intestine and the bloodstream. This condition can influence the carcass contamination during processing by:
  • The excess of proteins in the intestinal lumen supports higher contamination of pathogenic bacteria such as Salmonella sp and Campylobacter jejuni,
  • The higher amount of water in the gut lumen leading to more leaky excreta.

By mitigating mycotoxin risk, the opportunity for ‘leaky gut’ is minimized further supporting the production of safe poultry products.