David Ganskopp

Manipulating cattle distribution with salt and water in large arid-land pastures: a GPS/GIS assessment

Several of the problems associated with grazing animals in extensive settings are related to their uneven patterns of use across the landscape. After fencing, water and salt are two of the most frequently used tools for affecting cattle distribution in extensive settings. Cattle are attracted to water in arid regions, but mixed results have been obtained with salt and mineral supplements. The goal of this study was to evaluate the efficacies of salt and water manipulations for affecting cattle distribution in large (>825ha) pastures. This was accomplished by fitting cattle with global positioning system (GPS) collars and monitoring their travels and activities in a three pasture, Latin-square design where water and salt shared a common location and water or salt were moved individually to distant areas. Mean distance of cattle from water (&xmacr;=1.16km) was unaffected by treatments (P=0.79) suggesting that cattle followed movements of water tanks. Distance traveled daily (&xmacr;=5.78km), time devoted to grazing (11.0h per day), time devoted to resting (10.1h per day), and the area (&xmacr;=325ha) of minimum convex polygons were also unaffected by treatment implying that cattle did not compensate for separated water and salting areas with increased travels or disruptions of habitual grazing and resting activities. Centers of activity for cattle shifted further (P=0.02) when water (&xmacr;=1.49km) was moved than when salt (&xmacr;=1.00km) was relocated. Mean distance of cattle from salt increased from 1.03km, when salt and water were together, to 1.73km (P=0.08) when salt and water were separated. This implied that cattle made less effort to remain near salt. Also, when water and salt were separated, cattle were found within 250m of water 354 times and close to salt only 38 times. Movement of drinking water to distant points in pastures was the most effective tool for altering cattle distribution. When cattle and salt were introduced to a new portion of a pasture, cattle used the new area for about 2 days, and then began drifting back toward previously used portions of the pasture. Manipulations of salting stations will not significantly rectify serious livestock distribution problems in extensive arid-land pastures.

Inference of Animal Activity From GPS Collar Data on Free-Ranging Cattle

Abstract Global positioning systems (GPSs) enable continuous and automatic tracking of an animals position. The value of such spatial–temporal information can be improved if the corresponding activity of the animal is known. We evaluated the potential of Lotek GPS collars to predict activity of beef cattle on extensive rangeland in 2 contrasting foraging environments. Collars were configured to record animal location at intervals of 20 minutes (United States) or 5 minutes (Israel), together with counts from 2 motion sensors. Synchronized field observations of collared cows were conducted in 1999 (United States) and in 2002 and 2003 (Israel). Grazing, traveling (without grazing), and resting activities were recorded as minutes out of 20 for each category (United States), or as a single category (Israel). For the US data, stepwise regression models of grazing, traveling, and resting time accounted for 74%–84% of the variation, on the basis of the motion sensor counts for the left–right axis and the distances between GPS fixes. Regression tree analysis of grazing time yielded a simple model (4 splits) that accounted for 85% of the variation. For the Israeli data, the misclassification rates obtained by discriminant analysis and classification tree analysis of animal activity were 14% and 12%, respectively. In both analyses, almost all grazing observations were correctly classified, but other activities were sometimes misclassified as grazing. Distance alone is a poor indicator of animal activity, but grazing, traveling, and resting activities of free-ranging cattle can be inferred with reasonable accuracy from data provided by Lotek GPS collars.

Least-effort pathways: a GIS analysis of livestock trails in rugged terrain.

Livestock trails frequently evolve in pastures when plant growth or establishment cannot keep pace with vegetation disturbance. In some instances, man-made trails are established in rangeland settings to encourage uniform use of forages or facilitate livestock passage through dense vegetation or across rugged terrain. A long-term assumption has been that livestock establish pathways of least resistance between frequented areas of their pastures, but this hypothesis has never been tested. We mapped cattle trails in three 800+ ha pastures with global positioning units. A geographic information system (GIS) helped quantify characteristics of trails and the landscape and was used to plot least-effort pathways between water sources and distant points on selected trails in the pastures. Characteristics of the cattle trails and least-effort pathways were compared to test the hypothesis that cattle develop least-effort routes of travel in rugged terrain. The mean slope of the three pastures was 13.5%, and the average slope of the topography traversed by the cattle trails was 8%. The slope of the trails was reduced to 5.2% by selection of cross-slope routes. When we compared the characteristics of 10 selected cattle trails and least-effort pathways generated by our GIS, the cattle trails were 11% shorter (P=0.046) than the least-effort pathways, and the topography traversed by cattle had a gradient about 1% less than the least-effort pathways (P=0.02). The slope of the selected trails (5.5%) and pathways (5.6%) were similar (P=0.74), however. Analyses of values extracted from cost surfaces indicated that, on the average, 183 units of effort were needed to traverse the trails and 170 units of effort expended to traverse the least-effort pathways (P=0.07). These data support the hypothesis that cattle establish least-effort routes between distant points in rugged terrain and suggest that GIS software may be useful in designing systems of livestock trails in extensive settings.

GPS Error in Studies Addressing Animal Movements and Activities

Abstract 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 biasu200au200a=u200au200a0.18 mu200a±u200a0.12 m SE). When collars were immobile, GPS error generated about 1.7 mu200a±u200a0.7 m SE of perceived travel per record with postdifferentially corrected coordinates (Pu200a<u200a0.05), and 3.9 mu200a±u200a0.8 m SE with uncorrected data. At specific times, post-differential correction failures can affect (Pu200a≤u200a0.05) 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.

Response of cattle to cured reproductive stems in a caespitose grass.

Accumulation of wolf plants in rangeland pastures frequently results in waste or incomplete utilization of high quality forage by cattle. The objective of this research was to establish the degree of sensitivity of cattle to cured stems in crested wheatgrass (Agropyron desertorum (Fischer ex Link) Schultes) at 3 stages of phenology (late-boot, anthesis, and quiescence). This was accomplished by providing individual plants having densities of 0, 3, 6, 9, or 12 cured stems per dm2 basal area and measuring frequency and degree of utilization after exposure to cattle grazing. Project design was a split-plot in a randomized complete block with 3 replications, 3 stages of phenology as whole plots, and 5 densities of stems as treatments. A significant (P<0.01) phenology X treatment interaction occurred with cattle being equally sensitive to all treatments containing stems at late-boot and anthesis and oblivious to their presence at quiescence. At late-boot and anthesis stages of phenology 75% of plants with no stems were grazed while only 45% of plants with stems were grazed. Respective levels of utilization from the same treatments were 25 and 8%. A negative response was exhibited by cattle during anthesis when as little as 4% of biomass was contributed by cured stems. These results suggest that old growth stems should be removed or their presence noted as a covariate when conducting palatability studies or when observing plant-specific responses to defoliation by cattle. Cattle were not sensitive to treatments at quiescence when roughly 75% of plants in all treatments were defoliated with 25% herbage removal. This suggests that heavy grazing of a pasture with an objective of obtaining utilization of wolf plants would be most successful after all forage has cured, and cattle are less selective.

Selective differences between naive and experienced cattle foraging among eight grasses

Cattle are often required to adapt to new forages when they are moved to new pasture. The objectives of this research were: (1) to determine how rapidly naive cattle express clearly defined preferences when they encounter a new array of forages, and (2) to compare their evolving forage preferences and grazing behavior with those of experienced cattle. Three naive and three experienced yearling-steers were grazed in experimental paddocks supporting equal numbers of eight different caespitose grasses, and the number of visits to plants and number of bites harvested were monitored. Experienced steers immediately began grazing preferred forages, and throughout the trials, 90% of their visits were made to the two preferred grasses, giant wildrye (Elymus cinereus Scribn. and Merr.), and `Nordan crested wheatgrass (Agropyron desertorum (Fischer ex Link)Schultes). After the naive steers had sampled only nine individual plants, they selected the same two grasses as the experienced steers at significantly (P=0.05) higher frequencies than expected by chance. Diets of the naive steers, however, remained significantly different (P=0.001) from the experienced steers for the duration of the trials, so we could not determine the amount of exposure or time required for the selective patterns of the two treatments to approach parity. Across the 4-day trial, 97% of total bites by the experienced animals were from the two preferred grasses, while the naive animals took only 88% of their total bites from the same forages (P=0.001). Naive steers were also more likely to abandon a plant after harvesting a single-bite of forage (37%) than the experienced steers (19.5%). In approximately the same amount of time, naive steers harvested 21% fewer total bites than experienced animals, suggesting that naive animals were less efficient grazers. If naive cattle are introduced to an array of new forages, they may begin expressing dietary preferences paralleling those of indigenous animals within less than 5 min. Researchers, however, should not assume that naive cattle will provide an accurate depiction of the dietary composition of native stock, because naive cattle may sample a broader array of forages than their experienced counterparts and harvest fewer bites than experienced cattle from the preferred forages. Further research over more than 4 consecutive days will be required to determine the time necessary for `naive animals to be considered `experienced. These data also suggest that active cattle management may be focused on relatively few species even when pastures contain a heterogeneous mix of forages.

GPS Collar Sampling Frequency: Effects on Measures of Resource Use

Abstract 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 traveledu2009per 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 (Pu200a<u200a0.01) 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 (R2u200au200a=u200au200a0.93 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 (Pu200a<u200a0.001) distance traveledu2009per 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.

Preferences and behavior of cattle grazing 8 varieties of grasses

We compared the forage preferences of steers grazing among 8 varieties of grasses at 2 stages of phenology on the Northern Great Basin Experimental Range near Burns, Ore. Varieties included: ‘Nordan (Agropyron desertorum (Fischer ex Link)Schultes) and ‘CD-II’ (A. desertorum X A. cristatum (L.) Gaertner) crested wheatgrass; ‘Magnar’ and ‘Trailhead’ Basin wildryes (Leymus cinereus (Scribner & Merrill) A. Liive); ‘Golda? bluebunch wheatgrass (Pseudoroegneria spicata (Pursh)A. Liive); ‘Bozoisky-Select’ Russian wildrye (Psathyrostachys junceus (Fischer) Nevski); ‘Bannock’ thickspike wheatgrass (Elymus lanceolatus ssp. lanceolatus (Scribner & J.G. Smith) Gould), and ‘Secar’ Snake River wheatgrass (proposed nomenclature Elymus lanceolatus ssp. wawawaiensis (Scribner & J.G. Smith) Gould). Three esophageal-Bstulated steers grazed each paddock, with 3 paddocks grazed at the boot stage of development, and 3 paddocks grazed after grasses entered quiescence. In boot-stage trials, steers were very selective and collectively harvested 53% of total bites from the preferred CD-II and Nordan. These crested wheatgrasses also ranked higher (P 0.95, P < 0.01) with total bites harvested from varieties and are probably adequate for ranking relative preferences of steers. By selectively grazing at both stages of phenology, cattle diets were hlgher in CP, P, and ADL than the standing crop. During boot-stage trials, diets were also higher in Ca and Mg than forage analyses would suggest Except for phosphorus, the nutritive content of all varieties was satisfactory for lactating beef cattle at both stages

Seasonal preferences of steers for prominent northern Great Basin grasses.

The objective of this research was to determine, on a seasonal basis, the relative preferences of cattle for 7 native grasses and d crested wheatgrass (Agropyron desertorum (Fischer ex Link)Schultes), a long-used introduction in the Pacific Northwest. Methods involved observing forage selection processes of 3 steers in paddocks, where plants existed in equal densities and in rangeland pastures with variable forage composition. Design of paddock and pasture studies was a randomized-complete-block with 3 replications, 3 stages of phenology (vegetative, anthesis, and quiescent), and 8-11 forages. Dietary proportions as indexed by bite-counts changed (P < 0.01) with phenology and varied among species. Diets were more similar (P < 0.05) than forage composition between the 2 study areas (paddocks and native pastures), and became less similar (p < 0.05) as phenology of the grasses advanced from vegetative growth through anthesis and quiescence. Steers were selective grazers during vegetative and anthesis stages of phenology, and despite variations in herbage availability, Nordan crested wheatgrass was the most prominent dietary component in paddocks and pastures. Variation in proportions of grasses in the diet was associated (P < 0.05) with measures of available forage in the paddocks (r = 0.46-0.89, average = 0.72) but poorly associated with herbage composition in pastures (r = 0.41-0.02, average = 0.12). Inconsistencies in rankings of relative preference indices and dietary proportions of grasses suggested that measures of herbage availability may confound the predictive utility of relative preference indices. More grasses were acceptable to cattle at quiescence, with crested wheatgrass ranging from 8-26% of the diet. We suggest that with proper management, interseedings of crested wheatgrass on native range may be used to lessen grazing demands previously borne by native perennials early in the grazing season.

THURBER NEEDLEGRASS : SEASONAL DEFOLIATION EFFECTS ON FORAGE QUANTITY AND QUALITY

Although Thurber needlegrass (Stipa thurberiana Piper) is an important component of Palouse, sagebrush:steppe, and pine:forest rangelands, little is known of its qualitative and quantitative responses to defoliation. At 14-day intervals one of 7 cohorts of Thurber needlegrass plants was defoliated to a 2.5-cm stubble to describe initial growth rates, determine defoliation effects on subsequent regrowth accumulations, relate regrowth potential to available soil moisture, and determine the nutritional value of initial growth and regrowth for livestock. The study was conducted in 1985 and 1986 with a different group of plants used each year. Although crop-year precipitation for the 1985-86 treatment years was 77 and 111%, respectively, of the long term mean (25.2 cm), growth rates of tussocks were similar between years (P > 0.05). Seasonal yield of regrowth varied between years, however, and was well correlated (r2 = 0.76 to 0.80 P < 0.05) with soil moisture content when treatments were applied. Among 7 defoliation dates (24 April-17 July) only the first 5 yielded regrowth in 1985, and all produced regrowth in 1986. Among treatments regrowth averaged 22% of total herbage yield in 1985 and 50% of total yield in 1986. In both years total herbage accumulations were most suppressed (47-63% reduction) by defoliation during the early-boot stage of phenology. In 1985 when conditions were drier, any defoliation before mid-June depressed (P < 0.05) total herbage yield. Crude protein (CP) of needlegrass herbage was high (19-22%) when growth began in April but declined (P < 0.05) to marginal levels for cattle (6.7-7.7%) by mid-July. Regrowth harvested on 31 July ranged from 7 to 9% CP for the earliest (24 April) treatments and as high as 17% for the latest (17 July). Although Thurber needlegrass can produce highly nutritious regrowth for late-season use, managers face diminishing levels of regrowth as the initial cropping date is delayed later into the growing season. Managers contemplating 2-crop grazing regimes for Thurber needlegrass should base scheduling on plant phenology, soil moisture considerations and historic use rather than specific calendar dates. Further work is needed, however, to definitively determine Thurber needlegrass responses to long-term manipulative grazing regimes.