Short-term and Low Dose Deoxynivalenol Exposure Reduces Rainbow Trout Performance


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Deoxynivalenol (DON), a mycotoxin produced by Fusarium fungi, exerts negative effects on an animal’s gastrointestinal tract. The replacement of expensive animal-derived proteins such as fishmeal with cheaper plant sources in aquafeeds means that the most common mycotoxin globally is now creeping into aquaculture rations.

In fact, deoxynivalenol is present in 68% of aquafeed samples analyzed worldwide according to the new study.

Effects of deoxynivalenol in trout

According to Gonçalves et al. 2018, groups of Oncorhynchus mykiss fed DON-contaminated diets showed several clinical signs, including:

  • lesions on the skin
  • protruding anal papilla
  • hemorrhages
  • necrosis
  • hemorrhages of internal organs
  • degradation of some: liver and spleen

Experimental design

Four lots of rainbow trout were observed. Each lot received an identical diet with a different level of deoxynivalenol. The control group diet did not include the addition of mycotoxins. Two groups diets received high DON levels over a short term (50 days): one diet had a DON concentration of 1166 ppb (μg/kg) and the other contained 2745 ppb of DON. The fourth diet contained a low DON level: 367 ppb over 168 days—a scenario that most closely represents real production conditions.

Level of DON contamination impacts growth

During a short-term DON exposure, rainbow trout is sensitive to DON contamination. This sensitivity increases with the level of contamination. Thus, in a highly contaminated environment (2745 ppb DON) we note a significant decrease of growth performance parameters compared to a control sample (Figure 1). Deoxynivalenol (2745 ppb DON) have an impact on the final weight, the specific growth rate and the feed intake. 

Figure 1. Growth performance parameters determined in the short-term/high deoxynivalenol dosage study
Adapted from Gonçalves et al. 2018

Figure 1: Growth performance parameters determined in the short-term/high deoxynivalenol dosage study

DON exposure time and rainbow trout

Based on the study, we can confirm that a short period of DON exposure can have negative effects on the fish growth. However, a longer exposure at low level of contamination seems to be more representative of farmed rainbow trout conditions.

While low level DON exposure did not show a serious impact on fish during the first days of the experiment, we can notice harmful effect by the end of it in terms of lower final weight, as shown in Figure 2.

Figure 2. Growth curve representing the average weight of the fish during the long-term experiment
Adapted from Gonçalves et al. 2018

Growth curve representing the average weight of the fish during the long-term experiment

Difficult to pinpoint problem

The main challenge for producers is that fish do not present reliable clinical signs of low level deoxynivalenol exposure, which makes it difficult to spot a mycotoxin contamination problem. The lower performance over the long-term means less profit from a crop, however.

Detection is crucial

The main takeaway for aquaculture producers is that regular testing of feed ingredients for mycotoxins is crucial for identifying mycotoxin contamination. (Read Why You Should Test Your Feed for Mycotoxins).

Only through regular testing can producers take the necessary steps to protect their aquatic species and profits from mycotoxins.

References

Effects of deoxynivalenol exposure time and contamination levels on rainbow trout.
R. Gonçalves et al. Journal of the World Aquaculture Society, 2018.

https://doi.org/10.1111/jwas.12542