7 Myths and Truths about Zearalenone in Poultry Production

Poultry species are generally considered to be more resistant to ZEN than other species such as pigs. However, recent research has shown the potential hazard of this mycotoxin in poultry, not only in the reproductive tract but also in other systems and organs. 

According to the 2020 dsm-firmenich World Mycotoxin Survey, 67% of poultry feed samples analyzed between 2016 and 2020 were contaminated by ZEN (Figure 1). Interestingly, ZEN levels increased ) in both prevalence and average contamination levels over the last three years of this period (2018 – 2020.

Figure 1. Increasing ZEN prevalence (%) and concentrations (red numbers in ppb) in poultry feed in 2016 – 2020
Source: World Mycotoxin Survey, 2020

Deoxynivalenol (DON) and fumonisins (FB) are mainly produced by Fusarium sp., the same fungus that produces ZEN. Therefore, it is common to find these mycotoxins occurring in combination. Evaluating the complete situation is crucial: It has been proven that mycotoxins have negative synergistic effects, presenting  a challenge for the animal in reaching its maximum genetic potential.

Poultry are able to convert ZEN into α- and β-zearalenol (α- and β-ZEL). Fortunately, due to its rapid natural metabolization and excretion, poultry seem to be more resistant in comparison to other species such as swine or cow, but ZEN can still cause problems.

The α-zearalenol (α-ZEL) is considered the most toxic metabolite of ZEN.  Turkey poults have a significantly higher α-ZEL:ZEN ratio in comparison to broiler chickens and laying hens, meaning that more zearalenone is metabolized to toxic α-ZEL, supporting the hypothesis of increased sensitivity of turkeys to the estrogenic effects of the mycotoxin.

ZEN is known to cause alterations in the reproductive tract of layers and breeders. The estrogenic effect of ZEN is reflected in modifications of the reproductive tract of poultry species. In females the main findings are the presence of cystic oviduct, prolapse of the rectum and inflammation in the reproductive tract, while a reduction in testes size was observed in roosters. Moreover, alterations in egg shells and  frequent occurrences of cracked eggs in layers and breeders can indicate ZEN contamination of the feed.

Figure 2. Formation of cysts in the oviduct of breeders that received a diet contaminated with a high concentration of ZEN in the field
Source: Dr. Pavel Shkarlat, DVM, PhD

ZEN doesn’t just hurt birds’ reproductive systems. ZEN is also able to damage immune functions, induce oxidative stress and impact intestinal health in broilers. A recent study showed that ZEN is highly responsible for the increase of FCR in broilers when a natural contamination by mycotoxins, even in levels below EU recommendations. It also reflects the correlation between ZEN and broiler’s zootechnical performance.

Due to its low polarity, ZEN is considered a mycotoxin that cannot be adsorbed effectively (Figure 6) Therefore, using a simple binder wouldn’t be effective to protect the animal against ZEN’s effects. Research into new methods of counteraction have shown that enzymes are an effective strategy because they are able to break down the molecule into non-toxic metabolites.

Figure 6. Lower adsorption efficacy of Zearalenone

Remarks:

• It can be inferred that ZEN is a mycotoxin consistently present in the feed and its effects can induce reproductive disorders in breeders and layers.

• In addition, even low dosages of ZEN combined with other Fusarium toxins can affect the overall performance of poultry.

• Nevertheless, proven strategies other than adsorption should be implemented to counteract its effects.