Overview
This study measured heavy metals in 70 dairy cattle feed samples from two South African provinces (Free State and Limpopo) using ICP-MS. Arsenic, cadmium, and lead were all below the limits of detection across all samples. Chromium concentrations ranged from 0.032 to 1.459 mg/kg dry weight, copper from 0.092 to 4.898 mg/kg, and zinc from 0.39 to 13.871 mg/kg; all remained below WHO/FAO maximum limits for metal contaminants in animal feed. The findings suggest that dairy cattle feed in these two provinces does not represent a significant pathway for heavy metal carryover into milk and dairy products, though the study is geographically limited and does not cover all South African dairy production regions.
Key numbers
Measured concentrations (dry weight, ICP-MS, n=70 feed samples):
- tAs: below LOD in all samples (Free State and Limpopo)
- Cd: below LOD in all samples
- Pb: below LOD in all samples
- Cr (total): 0.032–1.459 mg/kg d.w. (Free State mean not separately reported; Limpopo mean not separately reported; range across both provinces)
- Cu: 0.092–4.898 mg/kg d.w.
- Zn: 0.39–13.871 mg/kg d.w.
WHO/FAO maximum limits in animal feed (for context):
- Pb: 5 mg/kg; Cd: 1 mg/kg; As: 2 mg/kg — all exceeded LOD-level findings by wide margin
- Cr: no universally agreed maximum; values in this study well below typical safety thresholds
Sample structure: 40 samples from Free State province (commercial dairy farms), 30 samples from Limpopo province (commercial dairy farms); feed types included total mixed rations, silage, hay, and concentrate mixes. LOD values reported for each analyte; all three primary HMT&C concern metals (As, Cd, Pb) were below LOD.
Methods (brief)
ICP-MS analytical method; dry weight basis; samples collected from commercial dairy farms in 2022–2023 (year estimated from publication date). Feed samples dried, ground, and acid-digested prior to ICP-MS analysis. LOD and LOQ values reported in the source; As, Cd, and Pb concentrations were uniformly below LOD across both provinces. The study notes that geographic and seasonal variation in feed composition may affect metal uptake from soil; the two provinces sampled are not representative of all South African dairy regions (Western Cape and KwaZulu-Natal, which have different soil geochemistries, were not included).
Implications
Certification: The uniform <LOD findings for As, Cd, and Pb in dairy cattle feed from these two South African provinces provides supply-chain context: feed-pathway carryover into milk appears negligible for these metals in this region. However, absence from two provinces does not constitute national-level clearance.
Courses: Illustrates the feed-to-food pathway concept: even when target metals are undetectable in feed, supply chain due diligence must account for regional soil geochemistry variability that may not be captured in a two-province study.
App: Dairy contamination profiles for Pb, Cd, and As should not be reduced on the basis of this one supply-chain-pathway study; direct milk/dairy product measurement data remains primary.
Microbiome: Not applicable.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |