Low-Cost Global Positioning System Tracking Collars for Use on Cattle

Commercially available global positioning system (GPS) tracking collars for cattle are cost prohibitive for most researchers. This paper presents a low-cost alternative to those collars (Knight GPS tracking collars) and compares their performance to a popular commercially available collar. A list of required materials and detailed instructions on fabrication are available in the supplementary content. Brangus cows (n = 8) were tracked with both LOTEK 3300 and Knight GPS tracking collars for 31 d beginning 14 March 2015 at the Chihuahuan Desert Rangeland Research Center 37 km north of Las Cruces, New Mexico. Locations were recorded every 10 min and used to calculate mean slope, elevation, distance from water, distance traveled per d, and elevation for each cow. No differences were detected (P ≥ 0.37) between collar types for location, slope, or distance from water. However, the distance traveled tended (P = 0.08) to be lower for Knight collars (6 171 m d^? 1) compared with Lotek collars (7 104 m d^? 1). Lotek collars recorded more (P ≤ 0.001) of the potential locations (99.9%) than the Knight collars (66.2%). Although the Knight collars failed to record all of the potential positions, they still provided a good indication of cattle locations on extensive pastures located in the Chihuahuan Desert.     

Technical Note: Method to Streamline Processing of Livestock Global Positioning System Collar Data

The use of global positioning system (GPS) technology to study livestock movement has been widely adopted in range and animal sciences; however, the methods for processing GPS collar data are varied among researchers and often involve repetitive, time-consuming steps to get data into a format available to view in geographic information system (GIS) software. The objective of this technical note is to present a method for quickly processing uniform datasets using a commonly available commercial GPS collar and Program R. Data generated by a Lotek 3300LR GPS collar were processed in seconds using “Lotek_Function,” which was developed using R coding. Traditional hand-processing of the same data generally requires 30 or more minutes and is prone to error due to the tedious, repetitive nature of the task. Due to the open-source nature of Program R, base codes can be modified to fit specific researchers’ needs when incorporating GIS data layers or models to assess behavior based on motion sensor data output from collars.     

GPS Error in Studies Addressing Animal Movements and Activities

Global Positioning System (GPS) error, associated with free-ranging animal studies, remains a concern in range/animal research. For distance measures, errors may be additive over time and increase as sampling frequency intensifies. The first study assayed effects of coordinate integration time (10 hourly intervals), 10 GPS collars, and range of unit movement (0 to 90 m in 10-m intervals as treatments) on bias of GPS measures of distance. “Bias” was the difference between measured distances and distances derived from GPS coordinates of units moved over a surveyed grid. A second study evaluated four methods (regression modeling, minimum distance threshold, motion sensor threshold, and a combined minimum distance/motion sensor technique) for extracting perceived movements from GPS data acquired from cattle. A classification assessment compared observation data of cattle with their corresponding GPS records after filtering by the four techniques. Except for immobile GPS collars in study 1, bias of distance measures was inconsequential for movements ranging from 10 to 90 m (differentially corrected mean bias = 0.18 m ± 0.12 m SE). When collars were immobile, GPS error generated about 1.7 m ± 0.7 m SE of perceived travel per record with postdifferentially corrected coordinates (P &spilt; 0.05), and 3.9 m ± 0.8 m SE with uncorrected data. At specific times, post-differential correction failures can affect (P ≤ 0.05) GPS measures of distance. Using any of four proposed techniques, one may effectively filter data sets to remove perceived travel accrued when cattle were resting with 81% to 92% of resting intervals correctly classified. The most effective regression technique suggested cattle travels were overestimated by about 15.2% or 1.15 km daily without filtering.     

Activity patterns of free-ranging beef cattle in Norway

The aims of this study were to: 1) build a model to classify cattle activities based on locomotion and neck movement data and 2) study the daily time budget of non-native beef cattle in the boreal forest of southeastern Norway. We used GPS collars programmed to take positions and activity measures every five minutes on 18 cows during the grazing seasons 2015–17, together with behavioural observations in the field. The model classified the collar data into Grazing, Low (resting behaviours) and High (other active behaviours) activity with an accuracy of 79.4%. The cows spent 8.1?±?0.5 (mean?±?SD) hours per day grazing, corresponding to 34%?±?0.5% of their daily time budget. Daily grazing time increased during summer and was longer for lactating than dry cows and at low compared to high stocking density.     

Automated Animal Control: Can Discontinuous Monitoring and Aversive Stimulation Modify Cattle Grazing Behavior?

Grazing livestock freely select landscape resources, unless they are herded or constrained by fences. Automated animal control (AAC) systems offer an alternative to physical fences by using animal-positioning technology and aversive stimuli to deter animals from staying in sensitive environments and so limit their impact. This paper reports on a replicated field experiment completed to test whether occasional stimuli (audio cue followed by a mild electric stimulus), delivered by discontinuously activated AAC collars, could suffice to modify the grazing behavior of groups of cattle. Four groups of eight steers were confined in 8-ha rectangular paddocks that had an ad libitum supplement feeder located in one end to attract cattle. The steers' positional information was recorded continuously for 3 d using a GPS receiver encased in a collar fitted around their neck. These data were used to characterize their use of the paddocks without intervention. Subsequently a restriction zone was activated on the collars. This zone contained the supplement feeders and represented approximately 10% of the paddock area. Cattle movement was again monitored during a second 3-d period, in which the steers were subjected to discontinuous aversive stimuli (5 min of stimulation followed by a random 0–30 min interval without stimulation) if they were located inside or moved into the restriction zone. Cattle visits to the restriction zone were shorter and the return interval longer when steers were subjected to discontinuous stimulation. Overall, there was a 97% reduction in the use of the restriction zone between the first and second deployments. These results suggest that grazing impact can be drastically reduced by making a zone less desirable through discontinuous aversive stimulation. Such a discontinuous (25% of the time on) AAC system can reduce power consumption in collars and so help overcome energy supply limitations that hinder commercial AAC applications.     

Grazing Management and Microclimate Effects on Cattle Distribution Relative to a Cool Season Pasture Stream

Because of concerns about the impact of grazing management on surface water quality, a 3-yr study was conducted to determine grazing management and microclimate impacts on cattle distribution relative to a pasture stream and shade. Three treatments, continuous stocking with unrestricted stream access (CSU), continuous stocking with restricted stream access (CSR), and rotational stocking (RS), were evaluated on six 12.1-ha cool-season grass pastures stocked with 15 fall-calving Angus cows (Bos taurus L.) from mid-May through mid-October of each year. On 2 d · mo^?1 from May through September of each year, a trained observer in each pasture recorded cattle position and activity every 10 min from 0600 to 1800 hours. In years 2 and 3, position of one cow per pasture was recorded with a Global Positioning System (GPS) collar at 10-min intervals 24 h · d^?1 for 2 wk · mo^?1 from May through September. In week 2 of collar deployment in May, July, and September, cattle had access to off-stream water. Ambient temperature, black globe temperature, relative humidity, and wind speed were recorded at 10-min intervals and temperature humidity (THI), black globe temperature humidity (BGTHI), and heat load (HLI) indices were calculated. Based on GPS collars, mean percentage of time cows in CSU pastures were in the stream (1.1%) and streamside zone (10.5%) were greater (P < 0.05) than cows in CSR (0.2% and 1.8%) or RS (0.1% and 1.5%) pastures. Based on GPS collar data, off-stream water did not affect the percentage of time cattle in CSU or CSR pastures spent in the stream. Probabilities that cattle in CSU and CSR pastures were in the stream or riparian zones increased (P < 0.05) as ambient temperature, black globe temperature, THI, BGTHI, and HLI increased. Rotational stocking and restricted stream access were effective strategies to decrease the amount of time cattle spent in or near a pasture stream.     

Cattle Grazing Distribution in Shortgrass Steppe: Influences of Topography and Saline Soils

The distribution of livestock across heterogeneous landscapes is often uneven, which has important implications for vegetation dynamics and how rangeland managers achieve desired outcomes from these landscapes. Here, we use data from widely available digital elevation models to classify a landscape in the shortgrass steppe with subtle topographic variation using two different approaches: topographic wetness index (TWI) and topographic position classes (TPCs) derived from topographic position indices. We used global positioning system collars to track the grazing locations of cattle within replicate pastures and fit generalized linear mixed models to their locations to quantify the influence of topography on grazing distribution. In addition, we examine the influence of the presence of saline vegetation communities on cattle use of lowlands. The resulting models indicate that TPC more effectively predicts grazing distribution than TWI and that the patterns are strongest in the second half of the growing season (August ? October). Model performance was improved with the inclusion of saline vegetation communities, although the magnitude of cattle grazing time in these communities was not consistent across multiple pastures. These models, in combination with local knowledge, can be used by managers to predict and manage livestock distribution even in landscapes with relatively subtle topographic variability.     

GPS Collar Sampling Frequency: Effects on Measures of Resource Use

A challenge in animal behavior studies using Global Positioning System (GPS) collars is selecting a sampling frequency to accomplish desired goals. High data resolution (i.e., frequent sampling) is appealing, because it maximizes behavioral information garnered. Extended sampling might be needed, however, to describe long term behaviors or seasonal dynamics. Because tradeoffs exist between high data resolution and sampling duration, we evaluated the effects of variable GPS sampling intervals on proportions of pastures used by cattle and distance traveled per day. This was accomplished with GPS collars configured to record cattle positions every 5 min for 15 d in three 829–864-ha pastures. Data were iteratively reduced to simulate increasingly longer GPS recording intervals from once every 10 min up to once daily. Two techniques were used to measure the percentage of pastures accessed by cattle. The first counted only pixels containing GPS coordinates. The second counted pixels containing coordinates and/or traversed by lines between vertices. Expansion of GPS recording intervals decreased (P < 0.01) estimates of the proportion of pastures visited by cattle with rates of decline best fit by exponential decay functions for both line and point techniques (R² = 0.93 and 0.97, respectively). Spatial errors accompanying less frequent sampling intervals, however, were extremely large with the line technique and misrepresented areas visited by cattle. Expansion of GPS sampling intervals decreased (P < 0.001) distance traveled per day by cattle about 10% with each iteration. If travel corridors or accurate assessments of resources accessed are of critical concern, then longer GPS integration intervals should be avoided because they propagate flawed spatial interpretations. Similarly, if accurate measures of travel distances are critical, we suggest using a relatively frequent GPS recording interval.     

Monitoring distances travelled by horses using GPS tracking collars

Objective The aims of this work were to (1) develop a low-cost equine movement tracking collar based on readily available components, (2) conduct preliminary studies assessing the effects of both paddock size and internal fence design on the movements of domestic horses, with and without foals at foot, and (3) describe distances moved by mares and their foals. Additional monitoring of free-ranging feral horses was conducted to allow preliminary comparisons with the movement of confined domestic horses. Procedures A lightweight global positioning system (GPS) data logger modified from a personal/vehicle tracker and mounted on a collar was used to monitor the movement of domestic horses in a range of paddock sizes and internal fence designs for 6.5-day periods. Results In the paddocks used (0.8–16 ha), groups of domestic horses exhibited a logarithmic response in mean daily distance travelled as a function of increasing paddock size, tending asymptotically towards approximately 7.5 km/day. The distance moved by newborn foals was similar to their dams, with total distance travelled also dependent on paddock size. Without altering available paddock area, paddock design, with the exception of a spiral design, did not significantly affect mean daily distance travelled. Feral horses (17.9 km/day) travelled substantially greater mean daily distances than domestic horses (7.2 km/day in 16-ha paddock), even when allowing for larger paddock size. Conclusions Horses kept in stables or small yards and paddocks are quite sedentary in comparison with their feral relatives. For a given paddock area, most designs did not significantly affect mean daily distance travelled.     

Effectiveness and comparison of citronella and scentless spray bark collars for the control of barking in a veterinary hospital setting

This study was designed to evaluate the efficacy of a citronella bark collar and a new, scentless spray bark collar in a veterinary hospital or a similar kennel-type environment. Forty-one dogs were included in the study. The efficacy of each collar was evaluated independently in comparison to control as well as in a crossover design. Thirty of the dogs were evaluated with the citronella collar, with 76.7% showing a reduction in barking. Twenty-nine dogs were evaluated with the scentless collar, with 58.6% showing a reduction in barking. The improvement over the control collars was statistically significant with both the citronella and scentless collars.     

Mitigating Human Conflicts with Livestock Guardian Dogs in Extensive Sheep Grazing Systems

Livestock guardian dogs (LGDs) are an effective tool for limiting livestock depredation by wild and feral predators. Unfortunately, LGDs have bitten hikers, joggers, and mountain bikers. Strategies are needed to mitigate LGD-human conflicts, especially in landscapes inhabited by large, aggressive predators where the threat of livestock depredation is greatest. One recommendation is to keep groups of sheep protected by LGDs at least 400 m from high-use recreational sites, but few data exist to support or refute this strategy. We monitored sheep and LGDs with Global Positioning System collars at seven ranches during a 3-yr period to evaluate how far, and under what circumstances, LGDs roamed from their sheep. One band of sheep (i.e., flock) was studied per ranch, with a typical band composed of 600−800 mature ewes with 900−1 200 lambs. Sheep were herded in extensive grazing systems within their traditional summer or fall grazing areas in foothill and mountain landscapes of southwestern and west-central Montana. Three bands of sheep inhabited landscapes with a greater threat of depredation by gray wolves and grizzly bears, and 4 bands of sheep inhabited landscapes where the threat of depredation was mostly from coyotes. The mean and median LGD-sheep distance across all LGDs and time periods was 164 m and 86 m, respectively. LGDs roamed farther from their sheep during nighttime and crepuscular periods than during daytime; farther when the moon was more fully illuminated; farther during fall than summer; and farther in landscapes without gray wolves and grizzly bears. Female LGDs roamed farther than males. Juvenile LGDs did not roam farther than adult LGDs. Overall, our results from extensive domestic sheep grazing systems suggest that keeping range sheep 400 m away from recreation sites and rural residences will likely prevent > 90% of agonistic LGD encounters with humans.     

Transdisciplinary habitat models for elk and cattle as a proxy for bovine tuberculosis transmission risk

Zoonotic diseases such as bovine tuberculosis (TB) that infect wildlife and livestock are particularly difficult to eradicate where wild animals make extensive use of agricultural landscapes. Transmission of TB between cattle (Bos taurus) and wild elk (Cervus elaphus) in southwestern Manitoba, Canada remains poorly understood but there is a risk when comingling occurs on summer pasture. Elk use of cattle summer pastures was assessed using ecological data (187 VHF and 25 GPS collared elk monitored over four years representing 8% of the elk population). Local knowledge was documented by conducting interviews and participatory mapping exercises with 86 cattle producers (98% of those within the study area). Of the 294 cattle pastures mapped by farmers, 13% were used by radio-collared elk, 38% were reported by farmers as being used by elk, and 42% were identified as used by elk when both when all datasets were combined. Cattle pastures that had been used by elk and those that had no elk were compared using binary logistic regression based on each of the three datasets (i.e. farmer observations, radio-collared elk on pasture, and combined dataset). For all three datasets, distance to protected area and proportion of forest cover on the cattle pasture were identified as the most and second most important predictor variables, respectively. There was strong agreement among the relative probabilities of elk occurrence on each pasture derived from the resource selection function (RSF) models developed using farmer interviews and elk collaring data. The farmer interview and collar datasets were then combined to generate a final integrated RSF map summarizing the probability of elk–cattle comingling and were contrasted over each of four cattle grazing seasons (spring, early summer, late summer, and autumn). These predictive maps indicate that use of cattle pastures by elk is extensive, particularly in spring and early summer. Farmer observations indicate that elk and cattle share water sources and livestock mineral supplements on pasture. Local knowledge and conventional ecological data complement and validate one another and help us better understand the temporospatial aspects of shared space use among wildlife and livestock and more generally the risks of disease transmission in agricultural landscapes.     

Impact of baiting on feral swine behavior in the presence of culling activities

We studied the effects of baiting on feral swine (Sus scrofa) movements and corresponding likelihood of disease spread under real and simulated culling pressure. Our objectives were to determine the proportion of feral swine that used the bait station site, and if baiting of feral swine altered areas of utilization, distances from location centroids to treatment location (control or bait station), and movement rates by survivors during culling activities. We hypothesized that the bait station would increase the sedentary nature of feral swine, thus reducing the potential for dispersal and hence disease dispersal. Our experiment was conducted between February and May 2011 on the Rob and Bessie Welder Wildlife Foundation (WWF) in San Patricio County, Texas. We trapped 83 feral swine and placed GPS collars on 21 animals. We established and maintained a centralized bait station on one side of the WWF from 13 March to 27 April. We conducted population-wide culling activities, including trapping, controlled shooting, drive shooting, and aerial gunning, from 3 to 27 April and removed 143 feral swine (4.6feral swine/km(2)). Areas of utilization did not differ between treatments (control or bait station). However, we found location centroids of bait station site feral swine to be closer to the treatment location than those of control site animals and daily movement rates of bait station site feral swine to be 39% greater than movement rates of control site animals. Based on our observation that only 62% of feral swine trapped in proximity to the bait station used it, we cannot recommend baiting as an alternative to fences for containing animals during culling activities. However, there is value in using bait stations to describe patterns of feral swine movements, facilitate observation, and improve efficacy when conducting removals.     

Predicting Spatial Risk of Wolf-Cattle Encounters and Depredation

Spatial variability in terrain, vegetation, and other features affect cattle and wildlife distribution on mountainous grazing lands of the western United States. Yet we have a poor understanding of how this spatial variability influences risk of wolf-cattle encounters and associated depredation. This knowledge gap severely limits our capacity to prevent or mitigate wolf-cattle conflict. Research addressing this problem was conducted in 2009−2011 at four study areas in western Idaho to evaluate models and mapping tools for predicting spatial risk of wolf-cattle encounters. Lactating beef cows grazing these study areas were instrumented with Global Positioning System (GPS) collars and tracked at 5-min intervals throughout the summer grazing season. Resource selection function (RSF) models, based on negative binomial regression, were developed from these GPS data and used to map the relative probability of cattle use in each study area. A wolf RSF model originally developed by Ausband et al. (2010) was applied to map study-area habitat types in terms of their relative suitability as wolf rendezvous sites. Spatial relationships between cattle and wolf selectivity patterns were used to classify and map wolf-cattle encounter risk to 5 classes (very high to very low) across each study area during the wolf rendezvous period (15 June−15 August). Validation analyses using GPS-based, wolf-cattle encounter observations (n = 200) revealed 84% of observed encounters occurred in areas of high- or very high−encounter risk (class 4 or 5). About 75% of confirmed wolf depredations recorded among three of four study areas were located in areas of high or very high risk. This new predictive understanding of wolf-cattle encounter risk will greatly aid livestock producers, resource managers, and policy makers in more effectively applying husbandry practices, allocating mitigation resources, and developing conflict mitigation plans and policies applicable throughout the mountainous western United States and potentially other regions of the world where wolves and cattle come into conflict.     

Efficacy of a collar impregnated with amitraz and pyriproxyfen for prevention of experimental tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs

OBJECTIVE: To compare the efficacy of collars impregnated with 9% amitraz or 9% amitraz and 0.5% pyriproxyfen (PPF) for control of newly established tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs and determine whether egg production by surviving female ticks was decreased. DESIGN: Prospective study. ANIMALS: 72 dogs. PROCEDURE: Dogs were fitted with 1 of 3 test collars impregnated with amitraz, amitraz and PPF, or only excipients (untreated controls). In 3 trials corresponding to each of the 3 tick species, dogs were infested with 150 unfed adult ticks on days 8, 10, 13, and 18. The number of feeding female ticks was recorded on days 10, 13, 18, and 28. Surviving females were weighed and permitted to oviposit under controlled conditions. RESULTS: Collars impregnated with amitraz and PPF decreased tick loads as efficiently as collars containing amitraz alone. Inclusion of PPF into the collar did not significantly decrease the efficacy of amitraz. The few female ticks that survived after feeding on dogs treated with collars containing PPF were unable to oviposit. CONCLUSIONS AND CLINICAL RELEVANCE: Collars impregnated with amitraz were efficient in preventing tick infestations in dogs but did not inhibit oviposition in the few surviving female ticks. Incorporation of PPF into the amitraz-impregnated collar resulted in impairment of the reproductive ability of ticks.     

山地牧道与植被空间异质性研究评述

山地牧道和沿牧道放牧改变植被空间异质性。综合国内外研究进展,将山地牧道的涵义扩展为家畜在山地垂直空间移动的固定路线、放牧往返小道、相对固定的采食路径以及践踏小径等,并总结了山地牧道的形成与分布规律,重点评述了山地牧道与植被空间异质性相互作用机制。山地牧道作为一种线状廊道,为物种扩散提供通道、生境,分割斑块景观,影响植被边界动态,在不同尺度上影响植被空间异质性;家畜沿牧道的选择采食与植被空间异质性相互影响,家畜还通过践踏和排泄改变植被空间异质性;家畜采食、践踏和排泄综合作用于土壤,通过影响土壤异质性间接影响植被的空间分布。山地牧道在动物行为学、放牧生态学研究中具有理论和实践价值,可以为监测植被退化、控制载畜量提供依据。     

Effects of pasture management and off-stream water on temporal/spatial distribution of cattle and stream bank characteristics in cool-season grass pastures

A 2-yr grazing experiment was conducted to assess the effects of grazing management on cattle distribution and pasture and stream bank characteristics. Six 12.1-ha cool-season grass pastures in central Iowa were allotted to 1 of 3 treatments: continuous stocking with unrestricted stream access (CSU), continuous stocking with stream access restricted to 4.9-m-wide stabilized crossings (CSR), or rotational stocking with stream access restricted to a riparian paddock (RP). Pastures were stocked with 15 fall-calving Angus cows (Bos taurus L.) from mid-May to mid-October for 153 d in 2008 and 2009. A global positioning system (GPS) collar recording cow position every 10 min was placed on at least 1 cow per pasture for 2 wk of each month from May through September. Off-stream water was provided to cattle in CSU and CSR treatments during the second of the 2 wk when GPS collars were on the cattle. A black globe temperature relative humidity index (BGTHI) was measured at 10-min intervals to match the time of the GPS measurements. Each month of the grazing season, forage characteristics (sward height, forage mass, and CP, IVDMD, and P concentrations) and bare and fecal-covered ground were measured. Stream bank erosion susceptibility was visually scored in May, August, and October (pre-, mid-, and post-stocking). Cattle in RP and CSR treatments spent less time (P < 0.10) within the stream zone (0 to 3 m from stream center) in June and August and in the streamside zone (0 to 33 m from stream zone) in May through August and May through September, respectively, than cattle in CSU pastures. However, off-stream water had no effect on cattle distribution. Compared with the CSU treatment, the CSR treatment reduced the probability (P < 0.10) that cattle were within the riparian zone (0 to 36 m from stream center) at BGTHI of 50 to 100. Bare ground was greater (P < 0.10) in pastures with the CSU than CSR and RP treatments in the stream and streamside zones in September and October and in July and September. Streams in pastures with the CSU treatment had less stable banks (P < 0.10) mid- and post-stocking than RP or CSR treatments. Results show that time spent by cattle near pasture streams can be reduced by RP or CSR treatments, thereby decreasing risks of sediment and nutrient loading of pasture streams even during periods of increased BGTHI.     

Evaluation of an accelerometer for at-home monitoring of spontaneous activity in dogs

OBJECTIVE:To determine the correlation between activity as measured by an accelerometer and videographic measurements of movement and mobility in healthy dogs. ANIMALS: 4 healthy dogs. PROCEDURES: After determination that accelerometers had good agreement, 5 identical accelerometers were used simultaneously to test their output at 8 locations (rotated among collar, vest, and forelimb stocking locations) on each dog. Movement and mobility for each dog were recorded continuously with a computerized videography system for 7-hour sessions on 4 consecutive days. Accelerometer values were combined into 439 fifteen-minute intervals and compared with 3 videographic measurements of movement and mobility (distance traveled, time spent walking > 20 cm/s, and time spent changing position by > 12% of 2-dimensional surface area during 1.5 seconds). RESULTS: 96% of values compared between the most discordant pair of accelerometers were within 2 SDs of the mean value from all 5 accelerometers. All mounting locations provided acceptable correlation with videographic measurements of movement and mobility, and the ventral portion of the collar was determined to be the most convenient location. CONCLUSIONS AND CLINICAL RELEVANCE: Use of an accelerometer was adequate for at-home activity monitoring, an important end point in clinical trials of treatment for chronic disease, and provided information about daily activity that is unattainable by other methods.     

Effects of the application of neck pressure by a collar or harness on intraocular pressure in dogs

The effect on intraocular pressure (IOP) from dogs pulling against a collar or a harness was evaluated in 51 eyes of 26 dogs. The force each dog generated while pulling against a collar or a harness was measured. Intraocular pressure measurements were obtained during application of corresponding pressures via collars or harnesses. Intraocular pressure increased significantly from baseline when pressure was applied via a collar but not via a harness. Based on the results of the study, dogs with weak or thin corneas, glaucoma, or conditions for which an increase in IOP could be harmful should wear a harness instead of a collar, especially during exercise or activity.     

SOME TOXICITY ASPECTS OF DICHLORVOS FLEA COLLARS IN CATS

SUMMARY The application of a dichlorvos flea collar to cats caused reduction of blood cholinesterase activity which reflected a generally slmilar reduction in the brain enzyme levels. The effects of the application of a single dichlorvos flea collar containing 500 mg of the insecticide were observed in 23 growing cats for periods of from 1 to 15 weeks. No overt signs of toxicity occurred and weight gain in young growing animals was not significantly affected. Whole blood cholinesterase was reduced within the first week of application of the collar and remained below pretreatment levels for 5 to 8 weeks before returning to normal presumably as the insecticide concentration in the resin was progressively reduced. Signs of systemic organophosphate toxicity did occur within 1 week of the application of three collars to each of two cats kept in the same cage. This suggested that the likelihood of toxicity occurring in cats following the use of dichlorvos flea collars depended mainly on the degree of exposure to the insecticide. Considering recent reports in the literature it was proposed that the environmental conditions of temperature (11? to 23?C) and relative humidity (50 to 65%) under which the experiments were carried out would have promoted a relatively low atmospheric concentration of dichlorvos in the near environment of the test animals and hence generally prevented occurrence of clinical signs. Under most conditions of keeping domestic cats in Australia the use of a single dischlorvos flea collar should therefore be without any untoward effect although some initial and translent inhibition of whole blood and nervous tissue cholinesterases would be expected.