Dietary Bentonite Supplementation Improves Growth Performance of Juvenile Nile tilapia Under Sub-Acute Aflatoxin B1 Exposure

Previous studies evaluating bentonite in Nile tilapia have largely employed high-dose AFB1 challenge models (≥2 ppm in the diet), whereas information on its efficacy under sub-acute contamination conditions is limited. This study evaluated the effects of a bentonite-based binder on growth performance and selected gross health-related indices in juvenile Nile tilapia exposed to 250 ppb dietary AFB1. In a 42-day feeding trial, 320 fish were randomly assigned to four treatments: a negative control (NC; no AFB1 or binder), a positive control (PC; 250 ppb AFB1), and two AFB1-contaminated diets supplemented with bentonite at 1 kg/ton (TMX-1) or 2 kg/ton (TMX-2). Dietary AFB1 exposure to 250 ppb impaired growth and feed intake and increased body-weight variability compared with the NC group (p < 0.01). Bentonite supplementation elicited inclusion-level-dependent responses. Fish fed TMX-2 had higher final body weight (+7.0%) and average daily gain (+7.9%) than those fed the PC diet (p < 0.01), whereas TMX-1 performed similarly to the PC group. Feed conversion ratio differed among treatments, with TMX-2 lower than TMX-1 (p = 0.02) but not significantly different from the NC or PC groups. Mortality, condition factor, body-weight variation and organosomatic indices did not differ among AFB1-challenged treatments. These findings indicate that dietary bentonite supplementation, particularly at 2 kg/ton, partially alleviated adverse responses associated with sub-acute AFB1 exposure, primarily through improvements in final body weight and average daily gain, in juvenile Nile tilapia under the conditions of the present study.