A model of cadmium accumulation in the liver and kidney of sheep derived from soil and dietary characteristics

Background: Cadmium accumulates in sheep tissues and often approaches the legal limit for human consumption in kidneys. Previous models have focused on transfer from plants to sheep but have restricted value due to seasonal and species variation in plant cadmium concentration. We created a model for the accumulation of cadmium in sheep using empirical relationships previously derived for accumulation in sheep kidney and liver from feeds, together with equations for accumulation in feeds derived from soil characteristics. The combined model relates soil cadmium to liver and kidney concentrations. Results: Sensitivity analysis demonstrated that the kidney accumulated cadmium faster than the liver and the greatest influence was the total cadmium concentration in the soil. The weight gain of the sheep and soil pH where the feed was grown had relatively minor influences on cadmium concentration in liver or kidney. Conclusion: A combined model of soil, plant and sheep kidney and liver characteristics enables concentrations of cadmium in sheep liver and kidney to be predicted from soil characteristics. This will enable the long-term risks of specific sites to be predicted with greater accuracy than if just plant cadmium concentrations were utilized