Exposure of pregnant dairy heifer to magnetic fields at 60 Hz and 30 µT

Abstract

Thirty-two pregnant Holstein heifers weighing 499 +/- 45 kg, at 3.1 +/- .7 months of gestation and 21 +/- 2.0 months of age were confined and exposed to 30 microT magnetic fields (MFs) and a 12 h light/12 h dark light cycle. The heifers were divided into two replicates of 16 animals. Each replicate was divided into two groups of eight animals each, one group the non-exposed and the second, the exposed group. The animals were subjected to the different treatments for 4 weeks. After 4 weeks, the animals switched treatment, the exposed group becoming the non-exposed group and vice versa. Then the treatment continued for 4 more weeks. Catheters were inserted into the jugular vein, and blood samples were collected twice a week to estimate the concentration of progesterone (P4), melatonin (MLT), prolactin (PRL), and insulin-like growth factor 1 (IGF-1). Feed consumption was measured daily. The results indicated that exposure of pregnant heifers to MF similar to those encountered underneath a 735 kV high tension electrical power line for 20 h/day during a period of 4 weeks produces slight effects. This is evidenced by statistically significant higher body weight (1.2%), higher weekly body weight gain (30%), and decreases in the concentration of PRL (15%) and IGF-1 (4%) in blood serum. The absence of abnormal clinical signs and the absolute magnitude of the significant changes detected during MF exposure, make it plausible to preclude any major animal health hazard.

Effects of Power-Frequency Magnetic Fields on Body Mass in Rats: A Pooled Analysis

“…Our results agree with previous findings that short-term powerfrequency magnetic field exposure causes an increase in the body mass of mice and cattle [1][2][3][4]18]. Electrical fields alone did not produce any change in the body mass of pregnant lactating cows relative to unexposed controls [19], whereas magnetic fields did [2].…”

“…There is some evidence that exposure of various animals, including mice and cattle, to a power-frequency magnetic field can increase body mass relative to unexposed controls [1][2][3][4]. This is a potentially interesting finding because the strength of the Earth's magnetic fields varies depending on latitude, and has varied over evolutionary time.…”

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

“…However, the study of Burchard et al (2004) did not confirm these results in which IGF-1 levels on pregnant dairy heifers exposed to 10 kV/M 60 Hz EF could not been detected significantly different than shamexposed groups. Nevertheless, in their recent study, slight decrease in concentration of IGF-1 of pregnant dairy heifer was reported with 60 Hz and 30 mT EMF exposures (Burchard et al, 2007). IGF-1 levels were found significantly lower in prenatal exposure group than the post-natal and sham-exposed groups in this study.…”

Influence of Electric, Magnetic, and Electromagnetic Fields on the Circadian System: Current Stage of Knowledge

“…The exposure of dairy cattle to a vertical electric field of 10 kV/m and a uniform horizontal magnetic field of 30  μ T for 28 days did not change the nocturnal blood melatonin level [86]. Similarly, no changes in melatonin secretion were observed in other experiments performed on dairy cows [87, 88] and on lambs [89, 90]. The studies of American kestrels reveled that a long-term exposure to electromagnetic fields (60 Hz, 30  μ T, 10 kV · m −1 ) caused changes in melatonin secretion [91].…”