Effect of electric and magnetic fields (60 Hz) on production, and levels of growth hormone and insulin-like growth factor 1, in lactating, pregnant cows subjected to short days.
← Research streamIn a crossover switchback study of 16 lactating, pregnant Holstein cows kept under short-day conditions, exposure to a 10 kV/m electric field and 30 microT magnetic field increased DMI and plasma IGF-1 (P < 0.01). Mean GH was not affected, though a treatment-…
Study snapshot
Abstract
Electric and magnetic fields (EMF) are generated by the transmission of electricity through high tension lines traversing rural areas. Previous studies showed increased dry matter intake (DMI) and fat corrected milk in dairy cows exposed to EMF. Because EMF exposure has been shown to suppress pineal release of melatonin in some species, it was hypothesized that EMF effects resemble those of exposure to long days. Previous studies have shown that DMI and milk production increase in dairy cattle in response to long day photoperiods, and this has been observed in association with increased circulating insulin-like growth factor 1 (IGF-1), but not growth hormone (GH). The hypothesis that EMF act by modifying the response to photoperiod was tested by subjecting dairy cows to controlled EMF exposure while keeping them under short-day conditions. Sixteen lactating, pregnant Holstein cows were exposed to a vertical electric field of 10 kV/m and a horizontal magnetic field of 30 microT in a crossover design with treatment switchback. Two groups of eight cows each were exposed to EMF for 16 h/d in either oftwo sequences. Each sequence consisted of three consecutive 28-d periods. All animals were maintained under short day conditions (8 h light, 16 h dark) during the trial. DMI and plasma IGF-1 were increased (P < 0.01) during EMF exposure (17.03 vs.16.04 kg/d, SE = 0.4; 137 +/- 6 ng/ml vs 126 +/- 6, respectively). The mean GH concentration was not affected, but a treatment x hour interaction was detected, with GH lower for the EMF exposed animals during the first 16 h of the sampling period, and higher for the last 8 h. Overall, the yield of milk or its components was not affected by EMF exposure, but milk yield was significantly higher for the exposed animals during wk 4 of treatment.
AI evidence extraction
Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.
Main findings
In a crossover switchback study of 16 lactating, pregnant Holstein cows kept under short-day conditions, exposure to a 10 kV/m electric field and 30 microT magnetic field increased DMI and plasma IGF-1 (P < 0.01). Mean GH was not affected, though a treatment-by-hour interaction was observed (lower during first 16 h, higher during last 8 h of sampling). Overall milk yield and component yields were not affected, but milk yield was higher during week 4 of treatment in exposed animals.
Outcomes measured
- dry matter intake (DMI)
- plasma insulin-like growth factor 1 (IGF-1)
- growth hormone (GH) concentration (including treatment x hour interaction)
- milk yield
- milk components yield
Limitations
- Animal study (dairy cows), not human health outcomes
- Short-day photoperiod conditions may limit generalizability to other lighting conditions
- Crossover switchback design details on randomization/blinding not provided in abstract
- Milk yield effects were not consistent across the full treatment period (overall not affected; week 4 difference reported)
View raw extracted JSON
{
"study_type": "randomized_trial",
"exposure": {
"band": "ELF",
"source": "high tension lines (simulated/controlled exposure)",
"frequency_mhz": null,
"sar_wkg": null,
"duration": "16 h/d; three consecutive 28-d periods per sequence (crossover switchback)"
},
"population": "lactating, pregnant Holstein cows under short-day photoperiod conditions",
"sample_size": 16,
"outcomes": [
"dry matter intake (DMI)",
"plasma insulin-like growth factor 1 (IGF-1)",
"growth hormone (GH) concentration (including treatment x hour interaction)",
"milk yield",
"milk components yield"
],
"main_findings": "In a crossover switchback study of 16 lactating, pregnant Holstein cows kept under short-day conditions, exposure to a 10 kV/m electric field and 30 microT magnetic field increased DMI and plasma IGF-1 (P < 0.01). Mean GH was not affected, though a treatment-by-hour interaction was observed (lower during first 16 h, higher during last 8 h of sampling). Overall milk yield and component yields were not affected, but milk yield was higher during week 4 of treatment in exposed animals.",
"effect_direction": "mixed",
"limitations": [
"Animal study (dairy cows), not human health outcomes",
"Short-day photoperiod conditions may limit generalizability to other lighting conditions",
"Crossover switchback design details on randomization/blinding not provided in abstract",
"Milk yield effects were not consistent across the full treatment period (overall not affected; week 4 difference reported)"
],
"evidence_strength": "low",
"confidence": 0.74,
"peer_reviewed_likely": "yes",
"keywords": [
"electric field",
"magnetic field",
"60 Hz",
"ELF-EMF",
"dairy cow",
"Holstein",
"dry matter intake",
"IGF-1",
"growth hormone",
"milk yield",
"photoperiod",
"short days",
"melatonin hypothesis"
],
"suggested_hubs": [
{
"slug": "occupational-exposure",
"weight": 0.32,
"reason": "Controlled exposure levels (electric and magnetic fields) relevant to power-line type environments, though studied in cattle."
}
]
}AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.
Identifiers and source
DOI: 10.3168/jds.s0022-0302(02)74371-3
PubMed: 12487451
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