Biological Effects of Electric and Magnetic Fields on Productivity of Dairy Cows

Abstract

Sixteen multiparous Holstein cows (weighing 600 +/- 50 kg, in 184.8 +/- 52 d of lactation, and at 101.9 +/- 43 d of gestation) were confined to wooden metabolic cages and exposed to a vertical electric field of 10 kV/ m and to a uniform horizontal magnetic field of 30 microT (microtesla). The trial was conducted as a switch-back statistical design. Cows were divided into two replicates of 8 cows each. One replicate was exposed for three periods of 28 d each. During the first period, the electric and magnetic fields were off; during the second period, they were on; and, during the final period, they were off. The second replicate was exposed for three periods also, but the activity of the fields was reversed (first period, on; second period, off; and third period, on). Blood samples were obtained twice weekly for the determination of cortisol and progesterone and once weekly for the determination of pH and blood gases. Milk samples were collected once weekly to determine milk components (fat, protein, SNF, and SCC). Milk yield and feed consumption were measured daily. Most of the variables studied (bicarbonate, pH, O2 and CO2 partial pressures, cortisol concentration in blood, uncorrected milk yield, and milk components other than milk fat) showed no variation that could be attributed to exposure to electric and magnetic fields. Associations were found between the electric and magnetic fields and increased DMI, 4% FCM yield, milk fat content, and plasma progesterone.

Effect of 10 kV, 30 μT, 60 Hz electric and magnetic fields on milk production and feed intake in nonpregnant dairy cattle

“…These results partially agree with previous results where E&MF were associated with a 5.5% increase in feed consumption and a 9% increase in fat-corrected milk yield in pregnant dairy cows exposed to 10 kV, 30 mT, 60 Hz E&MF (Burchard et al, 1996). However, no increase in feed consumption was observed in beef cattle exposed for 3 years to E&MF under a 500 kV DC transmission line (Raleigh, 1988).…”

“…The increase in DMI observed in the study reported herein is coincidental with an increase in milk fat content. Further statistical analysis of previous experiments (Burchard et al, 1996) revealed a significant week-by-treatment interaction for fat-corrected milk, DMI, and milk fat content. An analogous situation was observed when lactating pregnant dairy cows were exposed to E&MF (Rodriguez et al, 2002).…”

“…In fact, in some of the trials, the exposed cattle may have been receiving no E&MF exposure for days or portions of days because the current in the power lines varied, as did the distance of the cattle from the lines, both of which affect the intensity of the E&MF. Relatively few studies have been conducted in a controlled environment (Burchard et al, 1996(Burchard et al, , 1999Rodriguez et al, 1998Rodriguez et al, , 2002. These studies have suggested that dairy cows respond with certain physiological changes when exposed to E&MF similar to those generated by high tension lines.…”

“…These studies have suggested that dairy cows respond with certain physiological changes when exposed to E&MF similar to those generated by high tension lines. Burchard et al (1996) showed an increase in dry matter intake (DMI) and fat corrected milk in lactating, pregnant dairy cows exposed to E&MF (10 kV/m, 30 mT).…”

Environmental and social impacts of electricity utilization: broadening the debate

“…Exposure of lactating, pregnant dairy cows to the simulated environment of a 735 kV 60-Hz transmission line was reported by Burchard et al (1996). Using 12-h photoperiods and continuous EMF exposure, animals were held indoors in wooden stalls beneath electrified metal plates, mounted 2.6 m above ground level, providing vertical fields of 10 kV/m.…”