Previously, partial protection with 74mg/kg TCMN against AFB1 has been reported(11). However, increasing the supplemental levels of TCMN to 222 and 444mg/kg in the present study did not completely ameliorate the toxic effects of aflatoxin. The failure of increased levels of TCMN to
further ameliorate the toxic effects of AFB1 is not unexpected since oxidative damage is not the only mode of action of AFB1. For example, AFB1 has also been shown to decrease the expression of hepatic genes involved in energy production and fatty acid metabolism, detoxification, coagulation and immune protection of broiler chickens(22). The poor perform-
ance of chickens fed the diet containing 444mg/kg TCM with AFB1 could be attributed to the prooxidant action of curcuminoids at higher concentrations. Some polyphenolic compounds have been reported to exhibit both antioxidant and pro-oxidant functions due to metabolic transformations in the presence of transition metals like Cu and Fe(12,23).