Urbanisation threats to dairy cattle health: Insights from Greater Bengaluru, India

Overview

This study combined a structured interview survey of 151 dairy farmers in the Greater Bengaluru metropolitan area with chemical analysis of 92 lake-shore forage samples (alligator weed, Bermuda grass, para grass, water hyacinth, and mixed grasses) and 5 food-leftover samples fed to dairy cattle. The key finding is that 43% of the 97 analysed samples exceeded official threshold concentrations for at least one of four heavy metals (As, Cd, Cr, Pb), with Cr exceedance rates being particularly high: 92% of lake-fodder samples exceeded the WHO threshold of 1.30 mg/kg DM. The paper is primarily a veterinary and animal health study; direct relevance to the human food chain rests on the chain from contaminated fodder to cattle health to milk quality, which the authors explicitly identify as unknown and requiring follow-up. Evidence tier B is assigned because the journal is veterinary/animal science, not a food-safety analytical journal, and the human food-chain link is indirect and unquantified.

Key numbers

Heavy metal concentrations in lake fodder (n=92) and food leftovers (n=5), mg/kg DM:

Ranges: As 0.58–8.69, Cd 0.02–6.25, Cr 0.62–48.47, Pb 0.48–29.99 mg/kg DM.

By lake, Bellandur had notably higher Cd (1.81 mg/kg DM) and Cr (16.32 mg/kg DM) than most other lakes. Narasappanahalli had the highest Pb (13.09 mg/kg DM). No significant differences in As between lakes. Para grass showed consistently higher means across all four metals than other fodder types, though differences were not statistically significant.

Note: concentrations are in mg/kg DM (ppm DM), which equals 1,000 ppb DM. All values are total metals (ICP-OES, not speciated). Cr values are total chromium; Cr-VI data are absent.

Logit model finding: use of lake fodder was the strongest significant negative predictor of perceived cattle health (AME = -0.29, p < 0.01), stronger than insufficient drinking water (AME = -0.18) or high shed temperature (AME = -0.13).

Methods (brief)

Forage samples collected May 2022, microwave-assisted HNO3/HCl digestion; measurement by ICP-OES (Spectrogreen, SPECTRO). LODs: As 0.006, Cd 0.0001, Cr 0.00075, Pb 0.003 mg/L. Three technical replicates. CRM validation: ERM-CD281 rye grass (Cd, Cr, Pb within certified range). Inter-laboratory comparison of 10% of samples with AGROLAB LUFA GmbH; differences insignificant (P < 0.05). Basis: dry matter throughout. Total metals only; no speciation of As or Cr.

Implications

Certification: Indirect relevance. This paper does not measure metals in milk or milk products; it measures contamination in the feed inputs to dairy cattle producing urban milk. If contaminated fodder leads to carry-over into milk, this would affect dairy ingredient risk profiles, but that carry-over is uncharacterised. Not a direct evidence source for milk or dairy product concentration profiles.

Courses: Useful case study for supply-chain contamination pathways: urbanisation creates pressure on animal producers to use contaminated environmental forage, which may enter the human food chain through dairy. Illustrates Cr, Pb, and As co-contamination in urban lake vegetation at concentrations well above animal feed thresholds.

App: Not usable as a food-occurrence data source; the endpoint is cattle feed, not human food matrices.

Microbiome: Not applicable.

Wiki pages updated on ingest

• animal-feed-contamination
• Chromium
• Lead

Update history

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