Abstract

Phytogenics additives have gained considerable attention as efficacious and safe dietary interventions to reduce the toxic effects of aflatoxin B-1 contamination in aquatic animals. The present study was conducted to investigate the ameliorative efficacy of Thymus vulgaris essential oil on aflatoxin B-1 (AFB(1)) toxicity in rainbow trout (Oncorhynchus mykiss) in terms of growth performance, innate plasma immune indices and expression of immune related genes. Five experimental diets including a commercial diet as control, control diet +25 ppb AFB(1), control diet +50 ppb AFB(1), control diet +25 ppb AFB(1) + 1 garden thymus essential oil (TEO), and control diet +50 ppb AFB(1)+ 1 TEO were tested. Triplicate groups of fish averaging 20.77 +/- 0.08 g were fed the test diets at a rate of 3 body weight twice daily for 30 days. At the end of the experiment, fish fed TEO supplemented diets showed improved final weight, weight gain, feed conversion ratio and specific growth rates in comparison to groups received AFB(1) with no dietary TEO supplementation (P < 0.05). The biochemical (total protein) and innate immune (lysozyme and ACH50) parameters were significantly enhanced in all TEO supplemented groups (P < 0.05). Expression of tumor necrosis factor-alpha, transforming growth factor-beta and interleukin-8 were markedly up-regulated following feeding on diet containing high level of AFB1 (P < 0.05). Meanwhile, dietary TEO supplementation ameliorated the increased tumor necrosis factor alpha, transforming growth factor-beta and interleukin-8 expression induced by dietary AFB1 contamination (P < 0.05). However, TEO supplementation significantly enhanced interleukin-1 beta expression (P < 0.05). It can be concluded that, dietary supplementation of 1 TEO can mitigate the AFB1 induced suppression of growth and innate immunity in rainbow trout.