Effects of long-term exposure to a 400-kV, 50-Hz transmission line on estrous and fertility in cows

Abstract During recent years, concerns about high-voltage transmission lines have included possible direct influence on fertility of livestock reared near them. The objective of this study was to investigate, by an experimental design, the influence on reproductive performance in cows of a continuous long-term exposure to high-voltage AC transmission lines. The study comprised one exposed and one control group of 58 Swedish Red and White breed heifers each. Exposed animals were kept in three 44-m-wide enclosures beneath a 400-kV, 50-Hz transmission line, while control animals were kept in three similar enclosures off the line, each approximately 0.7 ha. The animals were put into the enclosures in the beginning of June and the inseminations started 24 days thereafter. The exposure time was, on an average, 120 days continuously. In the exposed group, the average exposure to the unperturbed electric field was measured and calculated to be 4 kV/m and that of the magnetic field to be 2 μT. Estrous was detected by systematic observations. Inseminations were carried out according to ordinary AI regions by the local AI centre, with semen from one single ejaculate. The parameters studied expressed length and regularity of the estrous cycle, mid-cycle plasma progesterone level, intensity of estrous, number of inseminations per pregnancy and proportion of animals conceiving. Also the proportion of fetuses showing heart activity shortly after slaughter of the dam was studied. None of the parameters were found to be influenced by the exposure of the heifers to the 400-kV, 50-Hz transmission line.