This in vivo study was performed to investigate the effects of low frequency magnetic field (comparable to this encountered underneath a 735 kV high tension electrical power line) in pregnant heifers concerning hormone concentrations, feed consumption, and body weight.
32 pregnant Holstein heifers (about two years age) were examined in trimester of pregnancy. The heifers were divided into two groups of 16 animals. Each group was divided into two subgroups of eight animals each (one group the non-exposed and the second, the exposed group). The animals were subjected to the different treatments for four weeks. After four weeks, the animals switched treatment, the exposed group becoming the non-exposed group and vice versa.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
60 Hz
Exposure duration:
20 h/day continuous for 2 x 4 weeks; with a two months intervall without exposure between the experiments
|
|
| Frequency | 60 Hz |
|---|---|
| Type | |
| Exposure duration | 20 h/day continuous for 2 x 4 weeks; with a two months intervall without exposure between the experiments |
| Exposure source |
|
|---|---|
| Chamber | chamber: 15 x 10 x 3 m, containing 8 wooden cages, each housing 1 animal |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 30 µT | - | measured | - | - |
The exposure of pregnant heifers to magnetic field produced slight physiological effects. This was evidenced by statistically significant higher body weight, higher weekly body weight gain, and decreases in the hormone concentration of prolactin and insulin-like growth factor.
The absence of abnormal clinical signs and the absolute magnitude of the significant changes detected during magnetic field exposure disprove any major animal health hazard.
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