The efficacy of three mycotoxin adsorbents to alleviate aflatoxin B1-induced toxicity in Oreochromis niloticus

Aflatoxicosis, toxicity of aflatoxin, is of great concern in aquaculture. This study was conducted to assess the efficacies of three adsorbents, a hydrated sodium calcium aluminosilicates (HSCAS), Saccharomyces cerevisiae (S.C.) and an esterified glucomannan (EGM), against feed contaminated with contained 200 mu g/kg (ppb) aflatoxin B-1 (AFB(1)). A total of 240 Nile tilapia fingerlings, Oreochromis niloticus (15 +/- A 2 g), were randomly divided into eight experimental groups (30 fish per group) with three replicates. Group T-1 represented the negative control fed on a basal diet, and T-2 was the positive control group fed on a basal diet supplemented with 200 ppb AFB(1). Groups T-3, T-4 and T-5 were fed the AFB(1)-contaminated diet (200 ppb) supplemented with 0.5 % HSCAS, 0.25 % S.C or 0.25 % EGM, respectively. Groups T-6, T-7 and T-8 were fed a basal diet supplemented with 0.5 % HSCAS, 0.25 % S.C or 0.25 % EGM, respectively. The reduction in AFB(1)-bioavailability was judged by toxin residues in fish musculature throughout the study beginning at the second week of exposure. AFB(1) reduced the survivability, total weight gain, average daily gain and specific growth rate, evident as early as the second week of exposure. The total erythrocyte count, hemoglobin content and total leukocyte count were significantly decreased after AFB(1) exposure for 6, 8 and 10 weeks, respectively. Prolonged administration of AFB(1) led to significant increases in serum alanine transaminase, aspartate transaminase and creatinine activity, and produced significant decreases in plasma proteins, including serum globulin. The specific immune response was assessed by an agglutinating antibody titer after immunization of the fish with an Aeromonas hydrophila vaccine. The antibody titer and relative level of protection of fish challenged with Aeromonas hydrophila were reduced throughout the period of examination in AFB(1)-exposed fish. Supplementation with HSCAS, S.C. or EGM significantly improved growth performance, blood parameters and immune status; in addition, these groups showed decreased AFB(1) residues in fish musculature when compared with AFB(1)-treated fish. HSCAS effectively reduced AFB(1) toxicity, whereas S.C. and EGM were less efficacious.