Individual and combined effects of deoxynivalenol (DON) with other Fusarium mycotoxins on rainbow trout (Oncorhynchus mykiss) growth performance and health.

This study assessed whether the toxicological effects of deoxynivalenol (DON) produced by Fusarium graminearum in rainbow trout (Oncorhynchus mykiss) are altered by the co-exposure to a mixture of toxins produced by Fusarium verticillioides (FU_mix). This FU_mix contained fusaric acid and fumonisin B₁, B₂ and B₃. Four diets were formulated according to a 2 × 2 factorial design: CON-CON; CON-FU_mix; DON-CON; and DON-FU_mix. Diets with and without DON contained on average 2700 and 0 µg/kg feed, respectively. The sum of the analysed FU_mix toxins was 12,700 and 100 µg/kg feed in the diets with and without FU_mix, respectively. The experiment consisted of a 6-week restrictive feeding period immediately followed by a 2-week ad libitum feeding period. Growth performance measurements were taken per feeding period. Histopathological measurements in the liver and gastrointestinal tract (pyloric caeca, midgut and hindgut) were assessed at the end of week 1 and week 6 of the restrictive feeding period and at week 8, the last day of the ad libitum feeding period. During both restrictive and ad libitum feeding, the effects of FU_mix and DON on growth performance were additive (no interaction effect; p > 0.05). During the restrictive feeding period, exposure to DON (p ≤ 0.001) and FU_mix (p ≤ 0.01) inhibited growth and increased feed conversion ratio (FCR). During this period, DON exposure decreased the protein (p ≤ 0.001) and energy retention (p ≤ 0.05) in the trout. During the ad libitum feeding period, FU_mix affected HSI (p ≤ 0.01), while DON exposure reduced feed intake (p ≤ 0.001) and growth (p ≤ 0.001) and increased FCR (p ≤ 0.01). In general, for both liver and intestinal tissue measurements, no interaction effects between DON and FU_mix were observed. In the liver, histopathological analysis revealed mild alterations, increased necrosis score by DON (p ≤ 0.01), increased glycogen vacuolization by FU_mix (p ≤ 0.05) and decreased percentage of pleomorphic nuclei by FU_mix (p ≤ 0.01). DON had a minor impact on the intestinal histological measurements. Over time, some of the liver (glycogen vacuolization score, pleomorphic nuclei; p ≤ 0.01) and intestinal measurements (mucosal fold and enterocyte width; p ≤ 0.01) were aggravated in fish fed the FU_mix contaminated diets, with the most severe alterations being noted at week 8. Overall, the co-exposure to FU_mix and DON gave rise to additive effects but showed no synergistic or antagonistic effects for the combination of DON with other Fusarium mycotoxins.