Evaluation of Tannic Acid for Disinfection of Rainbow Trout Eggs

Because of its bactericidal properties, tannic acid was evaluated as a potential egg disinfectant for rainbow trout Oncorhynchus mykiss. After water hardening, eggs were disinfected with tannic acid (2, 20, or 200 mg/L for 5 or 15 min) or with iodine (100 mg/L for 10 min; control). Hatch (83.7-93.4%) and deformity percentages (<0.8%) did not significantly differ among treatments. Bacteriological data indicated that the percentage of eggs with no bacteria was significantly higher from the iodine treatment (87%) than from the tannic acid treatments (29.2-50.0%). Therefore, we found that tannic acid was safe to use on rainbow trout eggs at concentrations of up to 200 mg/L for 15 min, but the control of bacteria was inferior to that provided by the standard iodine treatment.