Influence of high dietary α-tocopherol intakes on specific immune response, nonspecific resistance factors and disease resistance of healthy and aflatoxin B1 -induced immunocompromised Indian major carp, Labeo rohita (Hamilton)

Abstract

The effect of aflatoxin treatment and/or feeding of a high level of alpha-tocopherol on immune response and disease resistance was investigated in Indian major carp, Labeo rohita. Group A served as a healthy control, group B was treated with aflatoxin, group C was fed a high level of alpha-tocopherol whereas group D was exposed both to aflatoxin and a high level of dietary alpha-tocopherol for 60 days. Aflatoxin B1 (AFB1) was injected once intraperitoneally into fish on the first day of the experiment (groups B & D). High levels of DL-alpha-tocopherol (1000 mg kg(-1) feed) were provided to healthy as well as AFB1-treated immunocompromised fish for 60 days (groups C & D). At the end of the experiment blood samples were assayed for changes in nonspecific immunity and humoral protein levels. Disease resistance against two common bacterial pathogens viz., Aeromonas hydrophila and Edwardsiella tarda were evaluated in all groups. Significant (P < 0.05) suppression of specific immunity as measured through haemagglutination (HA) titre against sheep red blood cells (SRBCs) as well as bacterial (formalin-killed E. tarda) agglutination titre; nonspecific resistance factors viz., globulin level, serum bactericidal and lysozyme activities, neutrophil activities, and disease resistance against two bacterial pathogens only in aflatoxin-treated fish with respect to the control group, clearly indicated the immunosuppressive nature of aflatoxin. Feeding of a high level of alpha-tocopherol to AFB1-treated immunocompromised fish significantly (P < 0.05) raised specific immunity, nonspecific resistance factors and disease resistance capacity when compared with aflatoxin-exposed fish. Disease resistance and enhancement of immune status through feeding of high levels of alpha-tocopherol to healthy as well as AFB1-treated immunocompromised fish confirmed the potential of alpha-tocopherol in carp feed for prevention of disease and for combating natural/environmental immunosuppressants.