The effect of thyme and rosemary powder to improve the immunity of rainbow trout (Oncorhynchus mykiss) fed by aflatoxin B1 and zearalenone contaminated diet

Nowadays, the aquaculture industry is challenged with dietary mycotoxin contamination and their undesirable effects on fish. It is believed that feed containing antioxidants might be useful to modulate or even eradicate such problems. This study was to investigate the protective role of thyme and rosemary powder in the diet to reduce the toxic effects of dietary aflatoxin B1 and zearalenone contamination on some immune indices of rainbow trout fingerlings. Total number of 180 fish (3±0.2g) were allotted into three treatments including treatment one as control group (without toxin), treatment two received feed containing 50µg/kg aflatoxin B1 + 400µg/kg zearalenone and treatment three fed diet contaminated with 50µg/kg aflatoxin B1 + 400µg/kg zearalenone and contained 2% rosemary and 2% thyme powder (triplicate) for 4 weeks. The results showed that lysozyme and complement activity, serum total antibody content along with red and white blood cell counts were not affected by experimental diets (P>0.05). While lymphocyte proliferation and neutrophils phagocytosis indices and lymphocyte to neutrophil ratio were affected by treatments (P<0.05), as the lowest and the highest level of these indices, belonged to treatments two and three, respectively (P<0.05). The results showed that adding rosemary and thyme powder to mycotoxin contaminated diet could improve immune parameters of rainbow trout especially lymphocyte proliferation and lymphocyte to neutrophil ratio.