Toxicity and absorption of dietary leucomalachite green in Nile tilapia Oreochromis niloticus

Farmed fish are exposed to risks from feed-borne chemical contamination, such as leucomalachite green (LMG) in fish meal. Consequently, the use of malachite green is prohibited in aquacultural practice. An improved understanding of the toxicity of dietary LMG provided to farmed fish is needed in order to manage risk. Oreochromis niloticus specimens were fed experimental diets containing 0, 100, 500, and 2500 mu g/kg LMG for 28 days. On sampling days 7, 14, and 28, fish in the exposed groups had detectable levels of LMG. Accumulation levels were approximately 12.2 % (in the liver) and 6.2 % (in the muscle) of the LMG concentration in the feed (104, 510, and 2200 mu g/kg). Hematocrit and mean corpuscular hemoglobin concentrations in the 500 and 2500 mu g/kg groups were significantly elevated at 7 and 14 days. Hemoglobin in the group that received the highest dose was significantly higher than that in the control group. Significant increases in the activities of alanine aminotransferase and alkaline phosphatase were also detected in the group receiving the highest dose. Total cholesterol concentrations in all of the exposed groups were significantly higher than those in the control group. These observations of toxicity were dose dependent. Histological changes in gills and livers were observed in LMG-exposed fish.