Medical/biological study (experimental study)

Progesterone concentrations during estrous cycle of dairy cows exposed to electric and magnetic fields med./bio.

By: Burchard JF, Nguyen DH, Block E

Published in: Bioelectromagnetics 1998; 19 (7): 438-443

Aim of study (acc. to author)

To study the effects of electromagnetic fields on blood progesterone concentrations during estrous cycles in nonpregnant lactating dairy cattle exposed to maximal, continous, and uniform 60 Hz AC electromagnetic fields similar to those generated by 735 kV power lines.

Background/further details

16 cows were divided into two groups and exposed to electromagnetic fields. The length of each exposure period (21 to 27 days) varied according to the estrous cycle length. One group was exposed for three estrous cycles: During the first estrous cycle the electric and magnetic fields were off, during the second estrous cycle they were on, and during the third one they were off.
The second group was also exposed for three estrous cycles, but the exposure was reversed (first estrous cycle "on"; second estrous cycle "off"; third estrous cycle "on").
There was a 12:12 h light:dark cycle. Estrous cycles were synchronized with dinoprost-tromethamine injections.

Endpoint

endocrine changes: plasma concentration of progesterone

Exposure

- power transmission line

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: Two exposure sequences with each exposure period based on 21 to 27 days of estrous cycle; 1 and 2 sequences consisted of on/off/on and off/on/off exposure periods	magnetic flux density: 30 µT unspecified electric field strength: 10 kV/cm unspecified

Exposure 1

Main characteristics

Frequency	60 Hz
Type	electric field magnetic field
Waveform	sinusoidal
Exposure duration	Two exposure sequences with each exposure period based on 21 to 27 days of estrous cycle; 1 and 2 sequences consisted of on/off/on and off/on/off exposure periods
Additional info	Vertical electric field and horizontal magnetic field

Exposure setup

Exposure source	14 coils for MF and plates for EF generation
Chamber	Wooden metabolic cages
Setup	Coils (10 m long x 4 m high) generated uniform MF in the chamber. EF was generated by two plates (9 m long x 6.5 m wide) suspended 0.4 m from the ceiling by synthetic isolators.
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	30 µT	unspecified	unspecified	-	-
electric field strength	10 kV/cm	unspecified	unspecified	-	-

Exposed system:

animal
cow/Holstein
whole body

Methods Endpoint/measurement parameters/methodology

endocrine changes: plasma concentration of progesterone (radioimmunoassay); progesterone level in milk (to detect new corpus lutea); estrous cycles length (determined by the presence of a functional corpus luteum detected by concentrations of progesterone = or > 1 ng/ml)

Investigated system:

isolated bio./chem. substance
blood samples; milk

Investigated organ system:

endocrine system

Time of investigation:

during exposure

Main outcome of study (acc. to author)

No differences were found in plasma progesterone concentrations and area under the progesterone curve during estrous cycles between non-exposed and exposed periods. However, estrous cycle length was shorter in non-exposed cows than when they were exposed to electromagnetic fields.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Hydro-Québec, Canada

Dundar B et al. (2009): The effect of the prenatal and post-natal long-term exposure to 50 Hz electric field on growth, pubertal development and IGF-1 levels in female Wistar rats
Burchard JF et al. (2007): Exposure of pregnant dairy heifer to magnetic fields at 60 Hz and 30 microT
Burchard JF et al. (2006): Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields
Burchard JF et al. (2004): Lack of effect of 10 kV/m 60 Hz electric field exposure on pregnant dairy heifer hormones
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