Blood melatonin and prolactin concentrations in dairy cows exposed to 60 Hz electric and magnetic fields during 8 h photoperiods.

Bioelectromagnetics · 2004 · Mixed · Low evidence

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MixedLow evidencePaper 5217

Study snapshot

PublicationBioelectromagnetics · 2004

Study typeanimal

Reported directionMixed

Evidence ratingLow

Abstract

Two experiments were conducted to test the hypothesis that electric and magnetic field (EMF) exposure may result in endocrine responses similar to those observed in animals exposed to long days. In the first experiment, 16 lactating, pregnant Holstein cows were assigned to two replicates according to a crossover design with treatment switchback. All animals were confined to wooden metabolic cages and maintained under short day photoperiods (8 h light/16 h dark). Treated animals were exposed to a vertical electric field of 10 kV/m and a horizontal magnetic field of 30 microT (EMF) for 16 h/day for 4 weeks. In a second, similar experiment, 16 nonlactating, nonpregnant Holstein cows subjected to short days were exposed to EMF, using a similar protocol, for periods corresponding to the duration of one estrous cycle. In the first experiment, circulating MLT concentrations during the light period showed a small numerical decrease during EMF exposure (P < .05). Least-square means for the 8 h light period were 9.9 versus 12.4 pg/ml, SE = 1.3. Melatonin concentrations during the dark period were not affected by the treatment. A similar trend was observed in the second experiment, where MLT concentrations during the light period tended to be lower (8.8 pg/ml vs. 16.3 pg/ml, P < .06) in the EMF exposed group, and no effects were observed during the dark period. Plasma prolactin (PRL) was increased in the EMF exposed group (16.6 vs. 12.7 ng/ml, P < .02) in the first experiment. In the second experiment, the overall PRL concentrations found were lower, and the mean plasma PRL concentration was not affected by treatment. These experiments provide evidence that EMF exposure may modify the response of dairy cows to photoperiod.

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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.

Study typeanimal

Effect directionmixed

PopulationHolstein dairy cows (experiment 1: lactating, pregnant; experiment 2: nonlactating, nonpregnant) under short-day photoperiods (8 h light/16 h dark)

Sample size32

ExposureELF · 16 h/day for 4 weeks (experiment 1); for periods corresponding to one estrous cycle (experiment 2)

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

Across two experiments in Holstein cows under short-day photoperiods, EMF exposure (10 kV/m electric field; 30 microT magnetic field) was associated with lower melatonin concentrations during the light period (experiment 1: 9.9 vs 12.4 pg/ml, P<.05; experiment 2: 8.8 vs 16.3 pg/ml, P<.06), with no reported effect on melatonin during the dark period. Prolactin increased with EMF in experiment 1 (16.6 vs 12.7 ng/ml, P<.02) but was not affected in experiment 2.

Outcomes measured

Blood/circulating melatonin (MLT) concentrations during light and dark periods
Plasma prolactin (PRL) concentrations

Limitations

Animal study (dairy cows), not directly generalizable to humans
Two separate experiments with differing physiological status (lactating/pregnant vs nonlactating/nonpregnant) and differing exposure duration (4 weeks vs estrous-cycle period)
Some findings described as trends (e.g., P<.06) rather than clearly statistically significant
No effect on some endpoints/periods (e.g., melatonin during dark period; prolactin in experiment 2)

View raw extracted JSON

{
  "study_type": "animal",
  "exposure": {
    "band": "ELF",
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "16 h/day for 4 weeks (experiment 1); for periods corresponding to one estrous cycle (experiment 2)"
  },
  "population": "Holstein dairy cows (experiment 1: lactating, pregnant; experiment 2: nonlactating, nonpregnant) under short-day photoperiods (8 h light/16 h dark)",
  "sample_size": 32,
  "outcomes": [
    "Blood/circulating melatonin (MLT) concentrations during light and dark periods",
    "Plasma prolactin (PRL) concentrations"
  ],
  "main_findings": "Across two experiments in Holstein cows under short-day photoperiods, EMF exposure (10 kV/m electric field; 30 microT magnetic field) was associated with lower melatonin concentrations during the light period (experiment 1: 9.9 vs 12.4 pg/ml, P<.05; experiment 2: 8.8 vs 16.3 pg/ml, P<.06), with no reported effect on melatonin during the dark period. Prolactin increased with EMF in experiment 1 (16.6 vs 12.7 ng/ml, P<.02) but was not affected in experiment 2.",
  "effect_direction": "mixed",
  "limitations": [
    "Animal study (dairy cows), not directly generalizable to humans",
    "Two separate experiments with differing physiological status (lactating/pregnant vs nonlactating/nonpregnant) and differing exposure duration (4 weeks vs estrous-cycle period)",
    "Some findings described as trends (e.g., P<.06) rather than clearly statistically significant",
    "No effect on some endpoints/periods (e.g., melatonin during dark period; prolactin in experiment 2)"
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "ELF EMF",
    "60 Hz",
    "electric field",
    "magnetic field",
    "melatonin",
    "prolactin",
    "photoperiod",
    "dairy cows",
    "Holstein",
    "endocrine response"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.25,
      "reason": "Controlled exposure to 60 Hz electric and magnetic fields; relevant to ELF exposure scenarios (though in animals)."
    }
  ]
}

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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: 10.1002/bem.20024
PubMed: 15376244

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