The effects of exposure of dairy cows to an extremely low frequency electric and magnetic field on the estrous cycle should be investigated.
16 cows, which were synchronized in the starting points of their estrous cycle, were divided into two groups (only 13 cows analyzed; group 1: n=6 and group 2: n=7), each being assigned to a different exposure sequence. Each sequence consisted of three periods and each period corresponded to one estrous cycle. Group 1: sham exposure - exposure - exposure, and group 2: exposure - sham exposure - sham exposure.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
60 Hz
Exposure duration:
continuous for 16 h/day for up to 2 estrous cycles
|
|
| Frequency | 60 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 16 h/day for up to 2 estrous cycles |
| Additional info | vertical electric field horizontal magnetic field |
| Exposure source | |
|---|---|
| Chamber | chamber (15 m long, 10 m wide and 3 m high) containing eight wooden box stalls, each holding one cow |
| Setup | the magnetic field was generated by 14 rectangular coils, 10 m long and 4 m high; the electric field was generated by two plates, 9 m long and 6.5 m wide, that were suspended 0.4 m from the ceiling by synthetic isolators; a short photoperiod (8 h light/16 h dark) was provided during all exposure periods |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 10 kV/m | - | measured | - | - |
| magnetic flux density | 30 µT | - | measured | - | - |
The durations of the estrous cycle and luteal phase were found to be slightly but significantly longer under exposure conditions compared to sham exposure conditions.
The authors conclude that exposure of dairy cows to an extremely low frequency electric and magnetic field could increase the duration of the estrous cycle.
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