Mineral and potentially toxic element profiles in the soil-feed-animal continuum: Implications for public, environmental, and livestock health in three pasture-based sheep farming systems

Abstract

Grazing livestock derive most of their mineral requirements from foraging. The presence of toxic elements in soils has become a significant concern for food safety and ecosystem services. Understanding the mineral content profiles in soil and forage is crucial for assessing animal health, predicting potential transfers of minerals or heavy metals into the food-chain, and assessing threats to the environment and human health. In this study, Na, Mg, P, K, Ca, Mn, Fe, Co, Cu, Zn, Se, As, Cd, Hg, and Pb were measured to determine the mineral status of three different pasture-based farming systems (with grazing sheep livestock) in a Spanish region of significant economic importance. A risk assessment evaluation of animal, environmental, and human health was performed on soil, forage, feed, serum, milk, and wool. Notably, traces of Pb, and As were identified in pastures in all farms. Our calculation of pollution indices revealed moderate levels of contamination by various elements, including Co, Cu, Zn, Se, As, Cd, Hg, and Pb. The two farms with more intense agrosystem practices showed a significant potential ecological risk, characterized by high soil levels of Hg and Cd. Animals from these farms also had high concentrations of these metals in wool. Although the target Hazard Quotient derived from milk consumption suggests that dairy products from this area are safe for consumption for adults, only milk from a dehesa farm (mix of woodland and pastureland) was free of potential health concerns related to Pb exposure. Our assessment of mineral profiles reveals a cohesive relationship between soil quality and derived animal products, particularly of the Merino sheep breeding and farming system. The results reveal the importance of adopting and reinforcing strategies to preserve dehesas as a sustainable and environmentally friendly agrosystem in the western Mediterranean region.