Ensuring animals are provided safe feed stuffs is important in terms of animal health and welfare, environmental and financial considerations. Undesirable substances in animal feed can endanger animal health and, in case of carry-over of the substance in consumable animal products, also human health. Therefore, legislative maximum limits have been set within the EU for a number of potential contaminants in animal feed stuffs (2002/32/EC). To comply with these limits in the end products, control in every stage of the production chain is needed, starting at the initial source of contamination and covering all other relevant stages of the feed chain. The number of processes and stages will depend on the particular contaminant of concern, e.g., with heavy metals, it might go back to the soil or water resources.

Modelling the relevant supply chain stages is an effective tool for estimating the relative contribution of the various routes of contamination and their impact, as well as the effectiveness of potential intervention measures to control the contamination in final feed product. Such a modeling approach should include the stages of the chain of interest, the different contamination pathways, and carry-over coefficients.

Heavy metals, such as cadmium, copper and lead, are a group of contaminants that are of concern. In some areas in the Netherlands and other European countries diffuse pollution of cadmium has resulted in elevated levels in the soil. The presence of cadmium in soils used for the production of feed stuffs may result in high levels in the feed product due to uptake by the plant and consecutive accumulation in edible plants parts and in animals. The degree to which cadmium is available for plant uptake and further accumulation depends strongly on the degree of pollution and soil characteristics. In this regards, regional differences in soil cadmium levels and soil characteristics will result into differences in contamination of plants used for feed production.

The aim of the current study was to establish a quantitative supply chain model to estimate cadmium levels in animal products in different soil scenarios. The model integrates soil cadmium levels, soil characteristics, soil-to-plant transfer, animal intake, and transfer to animal products (meat, liver and kidneys). Cadmium content in roughage, cadmium intake and levels in the organs and in meat were calculated for six different soil scenarios, described by the level of cadmium in the soil and soil pH.

The estimated cadmium levels in roughage ranges between 0.16 and 1.50 mg/kg of fresh weight (FW) for maize and between 0.09 and 1.47 mg/kg of FW for grass, depending on the soil scenario. Only in the most extreme scenario did cadmium exceed the maximum tolerated level of 1.0 mg/kg of FW. Calculated cadmium levels in cattle kidney and livers range from 0.37-4.03 mg/kg of FW for kidneys and from 0.07 to 0.75m/kg of FW for livers. The maximum tolerated levels for both organs were exceeded for two soil scenarios (cadmium soil level of 2.5 mg/kg).