Study type: Medical/biological study (experimental study)

Effects of electric and magnetic fields on nocturnal melatonin concentrations in dairy cows. med./bio.

Published in: J Dairy Sci 1998; 81 (3): 722-727

Aim of study (acc. to author)

To study the effect of a uniform and controlled electromagnetic field on the nocturnal concentration of melatonin in the blood of cows.

Background/further details

16 multiparous, pregnant, lactating cows were divided into two groups (each group n=8): Both groups were exposed for three periods of 28 days each in a different order (fields "off" during the first period, "on" during the second period, and "off" during the final period or vice versa). On day 25 of each period, blood samples were obtained every 0.5 h for 14 h starting at 17.00 h to determine melatonin concentration.
The lights were turned off at 18.00 h and on at 06.00 h.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 60 Hz
Exposure duration: three periods of 28 days with either the sequence "power on - power off - power on" or "power off - power on - power off"

Exposure 1

Main characteristics
Frequency 60 Hz
Type
Exposure duration three periods of 28 days with either the sequence "power on - power off - power on" or "power off - power on - power off"
Exposure setup
Exposure source
  • coil(s)
  • two plates
Chamber 15 m x 10 m x 3 m chamber containing eight wooden metabolism crates each holding one cow (simultaneous exposure of eight cows)
Setup 14 rectangular coils, 10 m long and 4 m high, for generating the magnetic field; two plates (9 m long and 6.5 m wide), suspended 0.4 m from the ceiling by synthetic insulators, for generation of the electric field
Additional info The intensity of the electromagnetic field chosen was similar to a situation in which cows would stand continuously under a 735 kV alternating current power line when the line has a maximum load of current.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 30 µT - measured - horizontal field
electric field strength 10 kV/m - measured - vertical field

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

Melatonin concentrations of cows in group 1 were numerically greater during the "on" period, and, in group 2, values were greater during the "off" period (this difference was probably caused by the high variability in melatonin concentrations among cows).
In conclusion, the electromagnetic field exposure of 10 kV/m and 30 µT did not change the nocturnal concentration of melatonin in plasma of dairy cows.

Study character:

Study funded by

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