Two experiments were conducted. 1st with pregnant, lactating cows; 2nd with nonlactating, nonpregnant cows.
|Exposure duration||repeated daily exposure, 16 h/day for 4 weeks|
|Additional info||Experiment 1: Each animal was randomly assigned to one of the two sequences. Each sequence consisted of three exposure periods of 4 weeks. first sequence: OFF/ON/OFF; second sequence: ON/OFF/OFF.|
|Chamber||Exposure chamber (15 m x 10 m x 3 m ) containing 8 wooden box stalls each holding one cow|
|Additional info||The magnetic field was generated by 14 rectangular coils (10 m long x 4 m high) with the lower part of each coil embedded in the ground. Uniform electric field was generated by two plates (9 m long x 6 m wide) which were suspended from the ceiling by synthetic insulators.|
During the light period the melatonin concentrations in experiment 1 were found to be decreased in EMF exposed animals. However, no significant differences were observed in the dark periode. A similar trend was observed in experiment 2.
EMF exposure leads to significantly increased prolactin level in experiment 1.
The results of these experiments suggest that EMF exposure may alter the endocrine response of cows to photoperiod.