Thesis (M.S.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 12, 2009) Includes bibliographical references.

No description available.

This study was designed to determine the potential biological effects of electric and magnetic fields (EMF), generated by 735 kV alternating current (AC) high tension lines upon the hormonal profile, some health-related parameters, stress response and productivity in dairy cattle. An EMF exposure chamber to house eight animals at one time was constructed. Forty-nine cows were divided according to their production stage; 8 pregnant non-lactating cows, 16 pregnant lactating cows, 16 non-pregnant lactating cows and 9 non-lactating non-pregnant heifers. They were exposed to an EMF of 10 kilovolts per meter (kV/m) and 30 micro-Tesla $( mu T)$ in two different fashions: (a) for three consecutive periods of 28 days in two sequences either with the EMF on/off/on or off/on/off, in a switch back design; (b) for three consecutive periods with the sequence OFF (5 days), ON (30 days) and OFF (5-12 days). The intensity of the EMF chosen for the experiments resembled a situation in which the cattle are standing continuously under a 735 kV AC high tension line when the line has a maximum load of current. In reality, these conditions are found only for a few days during the winter in the Province of Quebec. / Milk production and composition, feed consumption, blood hormonal profiles and cerebrospinal fluid (CSF) components were assessed during the different periods of exposure. Most of the variables assessed were not affected by EMF. However, there was a positive association between EMF and feed consumption, milk fat content, blood plasma progesterone during pregnancy and estrous cycle length. Also, there were changes in the mineral and neurotransmitter metabolite concentrations in the CSF that showed a relationship to the EMF. / In conclusion, it could be stated that EMF caused a biological response in dairy cattle. It is speculated that these changes do not represent a health hazard for exposed cattle, although they warrant further research.

This study consisted of a series of experiments designed to test the hypothesis that exposure to extremely low frequency (ELF) electric and magnetic fields (EMF), similar to those generated by power transmission lines, can modify the response to photoperiod in dairy cows. Thirty two Holstein cows, 16 pregnant and lactating and 16 non-pregnant and non-lactating, maintained under short photoperiod (8 h light, 16 h dark), were exposed to an electric field of 10 kV/m and a magnetic field of 30 muTesla for 16 h/d, using cross-over experimental designs with three-period sequences. These exposure conditions resembled those prevalent under a 735 kV line carrying an extreme current load. Feed consumption, milk yield and composition, body weight, circulating concentrations of melatonin, prolactin, IGF-1 and growth hormone were assessed, as well as estrous cycle traits. A positive association was found between EMF exposure and feed consumption, uncorrected milk yield at the end of the exposure period and blood concentration of IGF-1. EMF exposure was also associated with an increase in blood prolactin concentration and decreased melatonin levels during the photophase in lactating pregnant cows. Non-lactating cows exposed to EMF showed longer estrous cycles. It was concluded that exposure to ELF EMF similar to those found under power transmission lines under extreme conditions of load elicits a biological response in dairy cows. Some aspects of this response are consistent with the hypothesis of a modification of the response to photoperiod.

No description available.

This thesis aims to develop a calculation method to determine themagnetic field magnitudes in the vicinity of power lines, i.e. bothburied cables and overhead lines. This is done through the numericaluse of Biot Savart's law where the conductors are approximated by aseries of straight segment elements that each contribute to the overallfield strength at the field point. The method is compared to two realcases and to the exact integral solution. Also, a review of some of theresearch material regarding electromagnetic fields from power lines andclaims of adverse health effects due to these fields is conducted.Results show that the numerical error is dependent on the segmentationdegree of the conductors and the mathematical model is inaccurate closeto the conductor. The calculations show slightly higher fieldmagnitudes than the previous survey done by WSP (Williams SalePartnership) far away from the source and slightly lower at the centerconductor. This may be due to the excluded induction in the shieldwires and differences in actual conductor coordinates.