Toxic and essential trace element concentrations in different tissues of extensively reared sheep in northern Spain

Abstract

Monitoring toxic and trace element concentrations in livestock, particularly in extensive farming systems, is important for obtaining information about the nutritional status of the animals as well as about nutritional value of the meat and the contents of potentially toxic element residues in the meat products. In this study, samples of liver, kidney and muscle (n = 253) were collected at slaughter from sheep reared in the Province of León (northern Spain), and the concentrations of the main toxic elements (arsenic, cadmium, lead and mercury) and trace elements (cobalt, chromium, copper, iron, manganese, molybdenum, nickel, selenium and zinc) were determined by ICP-MS. Overall, the concentrations of the toxic elements were within the ranges determined in other recent monitoring studies in sheep worldwide. They also reflected a similar background level of contamination to that observed for other livestock species reared in extensive production systems in the region. With the exception of cadmium in offal, toxic element residues were below the maximum limits established by the EU and thus do not pose any risk for human consumption. As in many other studies, the maximum levels established for cadmium (1 and 0.5 mg/kg wet weight for kidney and liver respectively) were exceeded in a high proportion of the kidney samples (24.0 %) and in a lower proportion of the liver samples (4.1 %) from adult animals. Essential trace elements concentrations were generally within the adequate–safe range established for sheep and were consistent with recently reported values. The only exception was copper, with concentrations indicating copper disorders in many of the liver samples (8.0 % indicating deficiency and 29.0 % toxicity). The concentrations of copper and its antagonists (molybdenum, iron and zinc) should therefore be carefully regulated in sheep flocks in northern Spain.