Hemato-immunological responses of juvenile tambaqui (Colossoma macropomum) after commercial clay dietary supplementation

The present study evaluated the physiological and biochemical responses of tambaqui (Colossoma macropomum) to different dietary supplementation levels of bentonite. We evaluated four treatments with three replicates (10 fish per tank). The sodium bentonite adsorbent (Buntech) was incorporated into the commercial feed at three levels in addition to the control group (0%, 0.5%, 1.0%, and 2%). After 10 and 20 days of feeding, we collected blood samples from five fish in each replicate for analysis. We observed the changes in hematocrit, hemoglobin, erythrocytes, and hematimetric indices of the tambaqui. Their glucose concentration, total proteins, total cholesterol, triglycerides, and albumin differed significantly due to the bentonite inclusion. We also recorded reductions in C. macropomum defense cells due to physiological damage caused by the adsorbent agent, resulting in thrombocytopenia, leukopenia, lymphocytopenia, and monocytopenia. Such reductions indicated a reaction and migration to inflammatory foci; the addition of this product did not reflect any improvement in the hematologicalbiochemical profile of this fish species. Our results suggest that sodium bentonite dietary supplementation has deleterious effects on C. macropomum and is not indicated as a food additive.