Influence of geographical location on the distribution of heavy metals in dairy cattle feeds sourced from two South African provinces

The contamination of feed and food by heavy metals represents a significant concern for the health of both animals and humans. This study investigates the impact of geographical location on heavy metal distribution in dairy cattle feeds sourced from Free State and Limpopo, South Africa (SA). A total of 70 feed samples (40 from Free State and 30 from Limpopo) were collected from 2018 to 2019 and analyzed for heavy metals, including cadmium (Cd), arsenic (As), copper (Cu), zinc (Zn), lead (Pb), and chromium (Cr), using inductively coupled plasma mass spectrometry (ICP-MS). Our findings revealed the presence of Cr, Cu, and Zn in the feeds, but at levels below the FAO/WHO permissible limits. Additionally, As, Cd, and Pb concentrations in the feeds were below the Limit of Detections (LODs). Generally, Cr concentrations (0.032–0.454 mg/kg) identified in the Free State samples were lower than those found in Limpopo (0.038–1.459 mg/kg), while the levels of Cu (0.092–4.898 mg/kg) and Zn (0.39–13.871 mg/kg) recorded in the Free State samples were higher than those from Limpopo [(0.126–3.467 mg/kg) and (0.244–13.767 mg/kg), respectively]. According to independent sample t-tests, Cu and Zn levels were substantially higher (p ≤.05) in Free State feeds compared to Limpopo, while Limpopo feeds exhibited significantly higher (p ≤.05) Cr concentrations than Free State feeds. Despite the low recorded heavy metal levels, regular monitoring of these elements in cow diets across all SA provinces is essential for ensuring the well-being of animals and humans.