Antagonistic effect of various dietary levels of Aflatoxin B1 and Zearalenone on digestive enzymes activity of fingerling rainbow trout (Oncorhynchus mykiss)

The formation of mycotoxins in feedstuffs is a worldwide issue affecting digestive physiology of aquatic animals and resulting in lower animal performance. Total of 540 rainbow trout with an average body weight of 3±0.2 g were allotted to 9 distinct treatments including various dietary levels of aflatoxin B1 (0, 25 and 50 ppb) and zearalenone (0, 200 and 400 ppb) for 4 weeks. At the end of the trial, pyloric ceaca samples were taken for determining alkaline protease, lipase and amylase activity. Results revealed that feeding on diets contaminated with aflatoxin B1 and zearalenone for 4 weeks did not significantly affect alkaline protease activity (p<0.05), however, did significantly affect lipase and amylase activity of rainbow trout fingerlings (p<0.05). The highest lipase activity was recorded in control group (feeding on diet devoid of any mycotoxins) and treatment co-contaminated with containing 25 ppb aflatoxin B1 or 200 ppb zearalenone. However, the lowest lipase activity belonged to treatments contaminated with only 400 ppb zearalenone or 25 ppb aflatoxin B1. The highest amylase activity was assayed in group fed on diet without any mycotoxin contamination in comparison to those fed diet contaminated with any levels (25 or 50 ppb) of aflatoxin B1 (p<0.05). It can be concluded that co-contamination with both aflatoxin B1 and zearalenone reduced their negative effect on lipase activity of fish.