Using cattle hair to assess exposure to essential trace elements in volcanic soils

Background: In areas where cattle graze outdoors, the environmental availability of trace elements is of utmost importance for an adequate intake. Cattle hair trace elements can be used as exposure biomarkers to assess animal intake and help ensure good nutrition and animal welfare. The aim of this study was to evaluate the environmental exposure to trace elements in cattle grazing outdoors in a volcanic region (Sa similar to o Miguel Island, Azores) and assess the corresponding bioaccumulation factors. Methods: Twenty-nine samples of pasture topsoil were collected in two areas of Sa similar to o Miguel with different geological characteristics: Picos fissure system (basaltic area) and Povoaca similar to o volcano (trachytic area). Hair from fifty-four animals (calves and dairy cows) was collected in two grazing sites: Ponta Delgada (Picos fissure system) and Povoaca similar to o (Povoaca similar to o volcano). All samples were analysed by inductively coupled plasma mass spectrometry (ICP-MS) after digestion in aqua regia. Results: Basaltic soils of the Picos fissure system had significantly higher concentrations of most trace elements, except Mo, when compared with the trachytic soils of Povoaca similar to o volcano. Hair of calves from Povoaca similar to o showed higher concentrations of most essential trace elements, except Mg, Cu, and Zn, than hair from calves of Ponta Delgada (considered in this study as a control group since they are raised in a barn). On the other hand, hair from dairy cows grazing in Ponta Delgada showed higher concentrations of most essential trace elements, except Mg, As, and Mo, when compared with hair of cows grazing in Povoaca similar to o. Conclusions: Cattle hair trace elements are suitable biomarkers for the assessment of the environmental exposure to trace elements in volcanic soils. The results from dairy cows support the uneven distribution of essential trace elements (and their bioavailability) in the different soils of Sa similar to o Miguel, reinforcing the need to graze animals outdoors from an early age. Such practice (grazing cattle outdoors) provides another means of accessing essential trace elements that complemented with feed can reduce the natural depletion of these essential elements in the body due to reproductive phenomena and milk production.