The modifying effect of multiple generation selection and dietary cadmium on methyl mercury toxicity in Japanese...

Japanese quails were exposed to dietary methyl mercury chloride in graded amounts from 2--8 ppm through a series of multiple-generation experiments with the experimental periods lasting from 6--12 weeks, starting with the experimental diets when the birds were 6 weeks old. Cadmium chloride was added to diets with and without mercury and fed to groups in three of the five experiments. Hatchability was depressed at 8 ppm mercury. The mortality of chicks from 8 ppm exposed parents was 100% in the first two generations, while chick mortality at the 4 ppm level in the same experiments was 54--63%. After six generations mortality in chicks hatched in 8 ppm group was reduced to about 50%. Cadmium supplementation at a level of 5 ppm counteracted the mercury-induced toxicity but failed to be effective in preventing the effects of mercury toxicity when added at 15 ppm level. Significant toxic effects of cadmium alone did not occur until the level was raised to 60 ppm. The morphology of mercury-induced encephalopathy was similar to the brain lesions reported in other bird species, with the injuries predominantly being localized to the cerebellar cortex and medulla.