Impact of feeder space on laying hen feeding behavior and production performance in enriched colony housing

Current feeder space recommendations in laying hen welfare guidelines are inconsistent among and within countries. One determining criterion forming the recommendations (e.g. 12.0 cm/hen for the EU guideline) is that all birds can feed simultaneously. However, if there are other resources in the environment, as in enriched colony housing (ECH), it is unknown whether group-housed hens will choose to feed simultaneously. This study assesses the impact of feeder space on feeding behavior of 60 laying hens (W-36) in ECH using a ultra-high frequency radio-frequency identification-based tracking system. The feeder spaces investigated were 12.0, 9.5, 8.5 and 6.5 cm/hen, achieved by blocking portions of the overall feeder access to keep hens at the same stocking density. Each feeder space treatment, randomly assigned over the course of the experiment, lasted for 7 consecutive days. Feeding behaviors were characterized as daily time spent at the feeder (TS, min/hen-day), daily frequency of visits to the feeder (FV, #/hen-day), and maximum or average percentage of hens feeding simultaneously (MPB, APB, %). Group-average daily feed intake (FI, g/hen-day), water use (WU, g/hen-day), and hen-day egg production (HDEP, %) were also measured. The results revealed that at 12.0 cm/hen, where unoccupied feeder space was present, a maximum of 59.0±1.4% (average of 31.7±0.3%) hens fed simultaneously. No significant differences were detected among 12.0, 9.5 and 8.5 cm/hen in TS (293±10, 286±10 and 281±10 min/hen-day) and MPB (59.0±1.4, 57.3±1.4 and 53.3±1.4%) (P>0.05). The outcome of no significant differences also held true between 12.0 and 9.5 cm/hen in APB (31.7±0.3 v. 30.8±0.3%) and between 9.5 and 8.5 cm/hen in all response variables measured (P>0.05). However, there were significant differences in APB between 6.5 cm/hen and all other treatments; in TS and FV between 6.5 and 9.5 cm/hen; and in MPB between 6.5 and 12 cm/hen (P<0.05). Considerable inter-hen variability was observed in TS (CV varying from 28.0% to 32.1%) and FV (CV varying from 26.5% to 27.8%). All the feeder spaces tested showed no significant impact on FI, WU or HDEP (P>0.05). The results revealed that synchronous feeding of hens in the ECH did not increase with increasing feeder space. However, it is worth noting that lower feeder space may lead to aggression or frustration which was not quantified in the current study.     

Inefficiency of electrosmog-shielding mats. Part 2: radio frequency range]

It could already be shown that electromagnetic shielding mats do not reduce but even enhance electric field exposure in daily life situations. By measurements and numerical simulations the claims of manufacturers were checked who pretend that radio frequency electromagnetic fields can be shielded to 99% and more, and transferred to earth by earth cables (if attached). It could be shown that in the radio frequency range such products do not fulfil the justified expectations of customers, but in most cases even cause the opposite. The results depend on the electric properties of the material. Good electric conductivity of shielding mats even considerably increases electromagnetic field exposure. To connect the mats with earth potential by an attached cable might increase the beliefs on a protective effect, however, this is not capable to enhance the shielding effect. The investigation demonstrates that in spite of references made to experts opinions manufacturers claims about the shielding efficiency of radio frequency fields are misleading and fool clients about the real situation. Overall, acquisition and use of electrosmog shielding mats must be discouraged. If at all, shielding can be reached by placing a shielding cover between the source and the person. However, even in this case, efficiency is much lower than promised by manufacturers and decreases even more if it is taken into account that the head naturally remains uncovered and hence unshielded.     

Measuring the drinking behaviour of individual pigs housed in group using radio frequency identification (RFID)

Changes in the drinking behaviour of pigs may indicate health, welfare or productivity problems. Automated monitoring and analysis of drinking behaviour could allow problems to be detected, thus improving farm productivity. A high frequency radio frequency identification (HF RFID) system was designed to register the drinking behaviour of individual pigs. HF RFID antennas were placed around four nipple drinkers and connected to a reader via a multiplexer. A total of 55 growing-finishing pigs were fitted with radio frequency identification (RFID) ear tags, one in each ear. RFID-based drinking visits were created from the RFID registrations using a bout criterion and a minimum and maximum duration criterion. The HF RFID system was successfully validated by comparing RFID-based visits with visual observations and flow meter measurements based on visit overlap. Sensitivity was at least 92%, specificity 93%, precision 90% and accuracy 93%. RFID-based drinking duration had a high correlation with observed drinking duration (R²=0.88) and water usage (R²=0.71). The number of registrations after applying the visit criteria had an even higher correlation with the same two variables (R²=0.90 and 0.75, respectively). There was also a correlation between number of RFID visits and number of observed visits (R²=0.84). The system provides good quality information about the drinking behaviour of individual pigs. As health or other problems affect the pigs’ drinking behaviour, analysis of the RFID data could allow problems to be detected and signalled to the farmer. This information can help to improve the productivity and economics of the farm as well as the health and welfare of the pigs.     

Behavioral indicators of slow growth in nursery pigs

The objective of this study was to determine how feeder-space allowance affects behaviors of slow- and fast-growing pigs during the nursery period. Nursery pigs (n = 192; initial weight = 7.4 ± 1.6 kg) were housed in 24 pens of 8 pigs, with 12 pens provided with either a two-space feeder or a five-space feeder. Pigs were categorized as slow growers (SG) and fast growers (FG) based on adjusted market weight (SG < 105 kg; FG ≥ 105 kg). Behaviors of pigs were video-recorded during the first four days after entering the nursery and on Day 21. Eating speed was measured on 96 focal pigs when they were nine weeks old. SG spent more time at the drinker than did FG (p < .05). SG spent less time in the standing/walking posture (p < .05) in pens with five-space feeders compared with SG in pens with two-space feeders. These results suggest that providing more feeder space may benefit SG in terms of improving the welfare of these pigs.     

Systems for exposing mice to 2,450-MHz electromagnetic fields

Two systems for exposing mice to 2,450-MHz electromagnetic fields are described. In a waveguide system, four mice were placed in a Styrofoam cage and exposed dorsally to circularly polarized electromagnetic fields. The temperature and humidity in the mouse holder were kept constant by forced-air ventilation. For 1-W input power to the waveguide, the average specific absorption rate (SAR) was determined by twin-well calorimetry to be 3.60 ± 0.11 (SE) W/kg in 27-g mice. The maximum SAR at the skin surface determined thermographically was 8.36 W/kg in the head of the mouse. The second system was a miniature anechoic chamber. Six mice were irradiated dorsally to far field plane waves. Copper shielding and high-temperature absorbing material were lined inside the chamber to accommodate the high input power. The air ventilation at the location of the mice was separately controlled so that any heating in the absorber would not affect the animals. For 1-W input power, the average SAR was 0.17 ± 0.01 W/kg and the maximum SAR at the skin surface was 0.41 W/kg in the animal when irradiated with body axis parallel to the E field; the SARs were 0.11 ± 0.01 W/kg and 0.64 W/kg, respectively, when irradiated perpendicular to the E field.     

A low‐cost radio frequency identification device for ornithological research

ABSTRACT Radio frequency identification (RFID) technology can be used to implement automated bird‐monitoring systems and, therefore, could be of use to field ornithologists. However, the cost of a large‐scale RFID network can be prohibitive for those with limited research budgets. We describe a simple RFID reader/data logger that can be constructed for less than $40 (excluding tools and a battery). This device can be mounted on birdfeeders, nest boxes, nests, or any location repeatedly visited by birds fitted with small RFID tags (i.e., passive integrated transponder or PIT tags). To demonstrate the potential of this low‐cost RFID reader, we monitored the use of feeders by wintering songbirds in central New York and generated a data set consisting of more than 500,000 feeder visits over 5 mo. These data revealed several interesting behaviors, including high visitation rates by some individuals (>200 visits per day), long‐distance movements between feeders (emigration and immigration), and species‐specific patterns of feeder use. Although the system performed well in relatively harsh winter conditions, occasional battery failures and water damage led to some loss of data. Nevertheless, we amassed over 8000 h of monitoring by investing approximately 6 h of labor per week. In addition to recording tag numbers and time stamps, the RFID reader can interface with sensors and actuators, permitting the collection of additional data (such as body mass) and allowing control of motors or solenoids to interact with targeted individuals. RFID technology has great potential for use in a variety of ornithological studies, and we hope our device helps make this technology more accessible.     

Automated tracking of wild hummingbird mass and energetics over multiple time scales using radio frequency identification (RFID) technology

We examined the feasibility of automating the collection of hummingbird mass data facilitated by low‐cost, low‐power radio frequency identification (RFID) technology. In a field study in southern Ontario, wild hummingbirds were captured, subcutaneously implanted with passive integrated transponder (PIT) tags, and released over a three‐year period. Tagged hummingbirds were detected at specially designed feeder stations outfitted with low‐cost, low‐power RFID readers coupled with a perch secured to a digital balance. When tagged birds visited the feeder, transponder detection initiated the recording of the perched hummingbird's mass at regular intervals continuing as long as the bird remained. This permitted a nearly continuous record of mass during each visit. Mass data collected from tagged hummingbirds showed consistent trends at multiple temporal scales: the individual feeder visit, single days, and even whole seasons. These results further confirm that RFID technology is safe for use in the smallest birds. The effective detection range is a function of RFID reader power, antenna, and tag size. Yet, we find that careful arrangement of feeders and detectors allows for reliable detection even when detection range is low. When coupled with additional technologies, such as a precision electronic balance, this approach can yield robust serial measures of physiological parameters such as mass, an indicator of energy balance over time.     

Effects of feeding frequency of an elevated plane of milk replacer and calf age on behavior,and glucose and insulin kinetics in male Holstein calves

Optimizing feeding regimens in early life to maximize lifelong growth and production are essential in the dairy industry. This study investigated the effects of milk replacer (MR) feeding frequency and calf age on behavior, and glucose and insulin kinetics of pre- and post-weaned calves fed an elevated plane of MR. Ten male Holstein calves (42.2±1.8 kg BW) were blocked by BW and randomly assigned to two treatments offering 8 l MR/day (150 g/l) in two (2×; meal size 4 l) or four (4×; meal size 2 l) feedings via an automated calf feeder. Milk replacer was gradually stepped down by 1 l/day during week 8, with calves being weaned by week 9. Water and pelleted calf starter were offered ad libitum. Individual intake of MR and starter were recorded daily, and BW was recorded weekly. The number of visits to the MR feeder (rewarded and unrewarded), and behaviors such as lying, cross-sucking, non-nutritive sucking and occupancy time in the feeder were recorded for individual calves from weeks 4 to 10. Jugular catheters were placed on weeks 4, 7 and 10 to facilitate postprandial blood sampling and glucose tolerance tests. Statistical analysis was conducted using the PROC GLIMMIX procedure (SAS) for behavioral observations, and the MIXED procedure (SAS) with repeated measures for BW, intake, plasma glucose and plasma insulin data. Final BW, starter and MR intake did not differ between treatments. There were no differences in observed calf behaviors; with the exception that 2× calves visited the MR feeder more often (P<0.01; total: unrewarded and rewarded). Baseline concentrations (mmol/l) and the maximum change in glucose (delta, mmol/l) were greater and lower (P=0.02) in 4×compared to 2×calves, respectively. Postprandial insulin AUC₂₄₀ tended (P=0.09) to be greater in 2×calves, compared to 4×calves at week 7. Similarly, T_max (min), AUC₂₄₀ and delta values (µU/ml) were greater (P⩽0.05) in 2×calves, compared to 4×calves. No treatment ×age interactions were observed for glucose or insulin during the glucose tolerance tests. Therefore, we conclude that feeding an elevated plane of MR (8 l/day) at a lower frequency (2× v. 4×) increased feeder visits, but not other hunger-related behaviors, and while postprandial glucose and insulin parameters varied, insulin sensitivity remained stable in Holstein dairy calves up to 10 weeks of age in calves consuming similar levels of calf starter.     

Inefficiency of electrical pollution-shielding mats. 1: low frequency range]

Despite of the fact that environmental electric and magnetic fields are magnitudes below the existing limits, fear from electromagnetic pollution increase and so does business with fear by offering more or less plausible products with partly excessively high prices . Based on numerical simulation the claims of manufacturers on the efficiency of electromagnetic shielding mats were tested. It is pretended that electric fields can be shielded to 98% and more, and transferred to earth by earth cables (if attached). It could be shown that in general such products do not fulfil the justified expectations of customers, but in contrary even cause the opposite. To connect the mats with earth potential by an attached cable might increase the beliefs on a protective effect, however, this is not capable to enhance the shielding effect but in most cases this causes even the contrary by partly considerably increasing electric field exposure. The electric conductivity of the used shielding mats plays a neglectable role and cannot explain the considerable price differences. The investigation demonstrates that in spite of references made to expert's opinions manufacturer's claims about the shielding efficiency are misleading and fooling clients about the real situation.     

Advances in cetacean telemetry: A review of single‐pin transmitter attachment techniques on small cetaceans and development of a new satellite‐linked transmitter design

Electronic tags have proven to be valuable tools in assessing small cetacean movement and behavior. However, problems associated with tag size and attachment have limited duration and damaged dorsal fins. These outcomes have motivated researchers to develop a new satellite‐linked tag design that reduces detrimental effects to tagged animals, while increasing transmission durations. The goals of this study were to review previous studies that deployed single‐pin transmitters and determine factors that influence transmission duration. Then, test these factors utilizing computational fluid dynamics (CFD) models to identify an optimal single‐pin satellite‐linked tag design, and evaluate this prototype through field studies. A review of four projects, which deployed 77 single‐pin radio tags, determined that tags attached along the lower third of the dorsal fin and approximately 33 mm from the trailing edge resulted in longer transmission durations and reduced negative impacts to the dorsal fin. Based upon these results and CFD modeling, prototype, single‐pin satellite‐linked tags (n = 25) transmitted for 163 ± 22 d (mean ± 95% CI) which greatly exceeded transmissions for previous small cetacean telemetry studies. These results suggest that the newly developed single‐pin satellite‐linked tag design strikes a balance between reducing impacts to the individual while maximizing transmissions.     

Daily variations in the thermoregulatory behaviors of naked neck broilers in an equatorial semi-arid environment

The aim of this study was to evaluate the daily variations in the thermoregulatory behavior of 4- to 6-week-old naked neck broilers (Label Rouge) in an equatorial semi-arid environment. A total of 220 birds were monitored for 5 days starting at 0600 hours and ending at 1800 hours. The period of observation was divided into classes of hours (C _H). The observed behaviors were as follows: feed and water intake, wing-spreading, sitting or lying, and beak-opening. A total of 14,300 behavioral data values were registered. In C _H 2 (0900 hours to 1100 hours) and 3 (1200 hours to 1500 hours), the greatest average body surface temperature was recorded (34.67?±?0.25 °C and 35.12?±?0.22 °C, respectively). The C _H had an effect on the exhibition of all behaviors with the exception of the water intake behavior. Feed intake was more frequent in C _H 1 (0600 hours to 0800 hours) and 4 (1600 hours to 1800 hours). In C _H 2 and 3, the highest frequency of sitting or lying behavior was observed. Beak-opening and wing-spreading behaviors occurred more frequently in C _H 3 where the body surface temperature (35.12?±?0.22 °C), radiant heat load (519.38?±?2.22 W m^?2), and enthalpy (82.74?±?0.36 kJ kg^?1 of dry air) reached maximum recorded averages. Thus, it can be concluded that naked neck broilers adjust their behavior in response to daily variations in the thermal environment. Wing-spreading and beak-opening behaviors are important adaptive responses to the thermal challenges posed by the equatorial semi-arid environment.     

Investigation of sleep disorders in the vicinity of high frequency transmitters]

To investigate the potential impact of RF electromagnetic fields of transmitters on the sleep quality of nearby residents, a new study design is presented. In a double-blind crossover field study the effect of on-site shielding, rather than of additional exposure, is investigated. For improved sleep quality differentiation the polysomnographic parameters are expanded by additional parameters. The feasibility study showed that checking the raw data and correcting the software-generated results by visual reading of the polysomnographic recordings is essential. Long-term RF measurement showed that exposure may vary considerably throughout the night, as well as from one night to the next. This variation may be greater than the GSM contribution itself. Mostly, the contributions of USW radio frequency fields dominated over GSM. Thus, continuous broadband RF recording is required for reliable interpretation of the results, in particular with regard to the potential role of mobile telephony emissions. Results show that simple sleep monitoring systems based on single-channel EEG analysis without acces to original biosignals are not adequate for sleep studies.     

Radio-frequency electromagnetic fields associated with cellular-radio cell-site antennas.

Because of a heightened public awareness of issues pertaining to the use of electromagnetic energy, concurrent with a rapid growth of the cellular telephone industry, a study was initiated to characterize the electromagnetic environment associated with typical cell-site antennas. In particular, the radio-frequency electromagnetic (RF) fields in the vicinity of several antenna towers, ranging in height from 46-82 m, were characterized by measurement. In all cases, the antennas were omnidirectional co-linear arrays. The maximal power densities considered representative of public exposure were found to be less than 100 microW/m2 (10 nW/cm2) per radio channel. Comparison of measured values with the corresponding values that were calculated from the free-space transmission formula indicated that the analytical technique is conservative (i.e., overestimates field levels). The measured and corresponding analytical values were found to be well below accepted exposure limits even when extrapolated to simultaneous and continuous operation of the maximal number of transmitters that would be expected to be installed at a cell-site. Additional measurements were made in the near field of the same antenna type in a roof-mounted configuration. At a distance of 0.7 m from the antenna, the maximal power density in the main beam was found to be less than 30 W/m2 (3 mW/cm2) when normalized to sixteen radio channels (the maximal number used on a single antenna) and less than 30 mW/m2 (3 microW/m2) at 70 m. In all cases, the effective radiated power (ERP) by each radio channel was 100 W referenced to a half-wave dipole. This paper describes the instrumentation and measurement techniques used for this study and provides a summary of the results.     

Pulsed radio frequency energy (PRFE) use in human medical applications

A number of electromagnetic field-based technologies are available for therapeutic medical applications. These therapies can be broken down into different categories based on technical parameters employed and type of clinical application. Pulsed radio frequency energy (PRFE) therapy is a non invasive, electromagnetic field-based therapeutic that is based on delivery of pulsed, shortwave radio frequency energy in the 13-27.12?MHz carrier frequency range, and designed for local application to a target tissue without the intended generation of deep heat. It has been studied for use in a number of clinical applications, including as a palliative treatment for both postoperative and non postoperative pain and edema, as well as in wound healing applications. This review provides an introduction to the therapy, a summary of clinical efficacy studies using the therapy in specific applications, and an overview of treatment-related safety.     

A preliminary study on ultra high frequency electromagnetic fields effect on black locust chlorophylls

Chlorophylls were quantitatively studied in the leaves of black locust (Robinia pseudoacacia L.) seedlings exposed to electromagnetic fields of high frequency. Exposure system was designed and built up to make possible simultaneous exposure of seedling lots (3 months old) to low power density electromagnetic fields corresponding to a frequency of 400 MHz. After three weeks of daily exposures (1, 2, 3 and 8 hours), chlorophyll levels were measured using adequate spectral device. Statistical analysis of experimental results was performed by means of t-test to identify significant modifications induced by electromagnetic treatment in exposed samples in comparison to the control. Chlorophyll-a as well as chlorophyll-b level was found to decrease except the exposure time of two hours, where a considerable enhancement was noticed. It was revealed that the ratio of the two main types of chlorophyll was decreasing logarithmically to the increase of daily exposure time.     

Numerical simulation of the electromagnetic fields excited by loop antennas in plasma in the whistler frequency range

The electromagnetic fields excited by circular loop antennas in a magnetized plasma in the whistler frequency range are simulated by the finite-difference time-domain method. The spatial structure of quasi-monochromatic fields excited in the near- and far-field zones by an antenna with a harmonic current, as well as the dynamics of the electromagnetic field excited by an antenna with a current in the form of a single video pulse, is studied. Simulations performed for a uniform plasma and uniform ambient magnetic field agree well with the results of theoretical analysis and model laboratory experiments performed on large-scale plasma devices.     

Specific absorption rate levels measured in a phantom head exposed to radio frequency transmissions from analog hand-held mobile phones

Electric fields (E-fields) induced within a phantom head from exposure to three different advanced mobile phone system (AMPS) hand-held telephones were measured using an implantable E-field probe. Measurements were taken in the eye nearest the phone and along a lateral scan through the brain from its centre to the side nearest the phone. During measurement, the phones were positioned alongside the phantom head as in typical use and were configured to transmit at maximum power (600 mW nominal). The specific absorption rate (SAR) was calculated from the in situ E-field measurements, which varied significantly between phone models and antenna configuration. The SARs induced in the eye ranged from 0.007 to 0.21 W/kg. Metal-framed spectacles enhanced SAR levels in the eye by 9–29%. In the brain, maximum levels were recorded at the measurement point closest to the phone and ranged from 0.12 to 0.83 W/kg. These SARs are below peak spatial limits recommended in the U.S. and Australian national standards [IEEE Standards Coordinating Committee 28 (1991): C95.1-1991 and Standards Australia (1990): AS2772.1-1990] and the IRPA guidelines for safe exposure to radio frequency (RF) electromagnetic fields [IRPA (1988): Health Phys 54:115–123]. Furthermore, a detailed thermal analysis of the eye indicated only a 0.022°C maximum steady-state temperature rise in the eye from a uniform SAR loading of 0.21 W/kg. A more approximate thermal analysis in the brain also indicated only a small maximum temperature rise of 0.034°C for a local SAR loading of 0.83 W/kg. © 1995 Wiley-Liss, Inc.     

Effect of polyphenols extracted from tamarind (Tamarindus indica L.) seed coat on pathophysiological changes and red blood cell glutathione peroxidase activity in heat-stressed broilers

The purpose of this study was to determine the effect of polyphenols extracted from the tamarind seed coat (PETSC) on glutathione peroxidase (GPx) activity, red blood cell parameters and bilirubin in heat-stressed broilers. One hundred forty-seven broilers, 18-days old were divided into two groups. In group 1, broilers were maintained at an environmental temperature of 26?±?2 °C throughout the experimental period. In group 2, the broilers were maintained at 38?±?2 °C (cyclic temperature: 26?±?2 °C; ?38?±?2 °C; and ?26?±?2 °C, and broilers were maintained at 38?±?2 °C for 6 h/ day) and received PETSC at a concentration of 0, 100, 200, 300, 400 or 500 mg/kg in their diet ad libitum. Parameters were investigated on days 1, 7, 14 and 21 of the experimental period. Results showed that GPx activity of heat-stressed broilers that received 100 mg/kg of PETSC in their diet was lower (P?<?0.05) than that in broilers fed the other concentrations. The mean total red blood cell count and hemoglobin concentration of heat-stressed broilers that received 100 mg/kg PETSC was higher (P?<?0.05) than those in broilers in group 1 and those fed the other concentrations. The mean bilirubin level in the excreta of heat-stressed broilers that received 100 mg/kg of PETSC was lower (P?<?0.05) than that in broilers that received 0, 300, 400 and 500 mg/kg of PETSC. This showed that PETSC could reduce GPx activity and bilirubin in feces, and increase red blood cell parameters in heat-stressed broilers.     

No effects of pulsed radio frequency electromagnetic fields on melatonin, cortisol, and selected markers of the immune system in man

There is growing public concern that radio frequency electromagnetic fields may have adverse biological effects. In the present study eight healthy male students were tested to see whether or not radio frequency electromagnetic fields as used in modern digital wireless telecommunication (GSM standard) have noticeable effects on salivary melatonin, cortisol, neopterin, and immunoglobulin A (sIgA) levels during and several hours after exposure. In a specifically designed, shielded experimental chamber, the circularly polarized electromagnetic field applied was transmitted by an antenna positioned 10 cm behind the head of upright sitting test persons. The carrier frequency of 900 MHz was pulsed with 217 Hz (average power flux density 1 W/m2). In double blind trials, each test person underwent a total of 20 randomly allotted 4 hour periods of exposure and sham exposure, equally distributed at day and night. The results obtained show that the salivary concentrations of melatonin, cortisol, neopterin and sIgA did not differ significantly between exposure and sham exposure.     

Extremely high frequency electromagnetic fields at low power density do not affect the division of exponential phase Saccharomyces cerevisiae cells

Exponentially growing cells of the yeast Saccharomyces cerevisiae were exposed to electromagnetic fields in the frequency range from 41.682 GHz to 41.710 GHz in 2 MHz increments at low power densities (0.5 μW/cm² and 50 μW/cm²) to observe possible nonthermal effects on the division of this microorganism. The electronic setup was carefully designed and tested to allow precise determination and stability of the electromagnetic field parameters as well as to minimize possible effects of external sources. Two identical test chambers were constructed in one exposure system to perform concurrent control and test experiments at every frequency step under well-controlled exposure conditions. Division of cells was assessed via time-lapse photography. Control experiments showed that the cells were dividing at submaximal rates, ensuring the possibility of observing either an increase or a decrease of the division rate. The data from several independent series of exposure experiments and from control experiments show no consistently significant differences between exposed and unexposed cells. This is in contrast to previous studies claiming nonthermal effects of electromagnetic fields in this frequency range on the division of S. cerevisiae cells. Possible reasons for this difference are discussed. Bioelectromagnetics 18:142–155, 1997. © 1997 Wiley-Liss, Inc.