Plant-based feed ingredients are often con- taminated with mycotoxins, causing health risks.

represents the first barrier against feed contaminants, such as DON, but few studies have focused on the effects of DON on the digestive tract of aquatic animals. Deoxynivalenol levels of 0.5 and 1.0 ppm in the diet significantly reduced body weight and growth rate in white shrimp, while FCR and sur- vival were not affected. In fish, a study showed that rainbow trout had sensitive taste acuity for DON and reduced their feed intake as the DON concentration in the diet increased from 1 -13 ppm, resulting in reduced growth and feed effi- ciency. Another study observed that weight gain, feed intake and feed efficiency (FE, gain:feed) of trout decreased signif- icantly (p<0.05) with increasing levels of DON in the diets, starting at levels of 0.5 ppm. Significant histopathological changes in the liver and intestine with increasing dietary levels of DON were also reported. Atlantic salmon diets with 3.7 mg/kg of DON resulted in a 20% reduction in feed intake, 18% increase in FCR and a 31% reduction in specific growth rate. DON causes oxidative stress in cells by damaging mi- tochondria function through the excessive release of free radicals, including reactive oxygen species (ROS) that induce lipid peroxidation or decrease antioxidant enzyme activity. Rapidly proliferating cells with a high protein turnover, such as immune cells, hepatocytes and epithelial cells of the diges- tive tract, are predominantly affected by DON.

How can we protect fish from the impacts of mycotoxins? At present, one of the most effective and commonly used approaches is introducing feed additives with mycotoxin mitigation properties to reduce toxic effects within the ani-

40 ▶ ALL ABOUT FEED | Volume 29, No. 5/6, 2021

mal. A recent example of successful mycotoxin mitigation in aquatic species was reported in a study of turbot at the Ocean University in China. Researchers investigated the ef- fects of dietary DON on the growth performance, immune response and intestinal health of turbot and the mitigation efficacy of yeast cell wall extract (YCWE, Mycosorb) to meet this challenge. The study showed that a diet contaminated with 3 mg/kg DON significantly reduced the weight gain, specific growth rate and feed efficiency ratio of fish (Table 1) and reduced im- munoglobulin M and complement 4 concentrations in serum. Contaminated turbot diets caused alterations in detoxifica- tion capacity; lower activity of superoxide dismutase, catalase and total antioxidant capacity but higher malondialdehyde content and gut barrier; lower expression of tight junction proteins (claudin-4 and occludin) and immunity and higher expression of interleukin-1β in the intestine. Additionally, DON-contaminated diets reduced the abundance of potential helpful bacteria and increased the abundance of potential pathogens found in the intestine. The addition of YCWE, par- ticularly to diets contaminated with 3 mg/kg DON and sup- plemented by 0.2% YCWE, markedly improved growth perfor- mance (Table 1), immune response and enhanced the intestinal health of the turbot. The current study showed that dietary YCWE lessened the toxic effects caused by dietary DON in turbot and has the po- tential to be used as an effective strategy to mitigate the neg- ative impacts of DON in fish feed.

Full list of references available on request.


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