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.
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.
|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|
|Additional info||Vertical electric field and horizontal magnetic field|
|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.|
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.