Short‐term effects of cattle‐to‐sheep ratio and stocking rate on patch grazing in sour grassveld

Abstract

The short‐term effects of stocking rate (AUE ha^?1) and cattle‐to‐sheep ratio on the extent and severity of patch grazing and on patch size were evaluated. The extent of patch grazing was proportional to stocking rate, and livestock species had a small but significant effect. Patch size was also a function of stocking rate. Cattle and sheep had similar effects on patch size distribution when stocked at the same number of AUE ha^?1. The severity of grazing within a patch was influenced by both stocking rate and cattle‐to‐sheep ratio. Recommendations that cattle should be grazed together with sheep and that cattle should be in greater proportion (in terms of AUE ha^?1) than sheep, which are aimed at limiting the severity of grazing by sheep, are supported. However, severe grazing within patches is an inevitable consequence of sheep grazing irrespective of the stocking rate or cattle‐to‐sheep ratio applied.     

放牧牦牛行为及其对高寒草地土壤特性的影响研究进展

放牧牦牛是对高寒天然草地的一种重要的利用方式,牦牛通过采食牧草、践踏土壤和排泄粪尿等行为可能对草地生态系统产生不容忽视的直接或间接影响。通过归纳分析放牧牦牛行为及其生态环境效应的有关研究成果,系统论述了牦牛采食牧草、践踏土壤和排泄粪尿3种主要行为的表现特性及其对草地土壤理化和生物学性质的影响效应和作用机制,阐明了高寒草地土壤碳氮养分、植被生物量及微生物群落等对牦牛践踏和粪尿排泄物返还的响应特征及差异性。指出牦牛采食、践踏和粪尿排泄是影响草地物质循环和能量转换的重要环节。未被消化利用的牧草养分通过粪尿排泄返还到草地土壤中,被认为是对养分匮缺的天然草地的一种重要的施肥措施,也是维持土壤养分平衡和植被生产力的重要保障。而畜蹄践踏相对于采食和排泄行为而言具有作用时间长、直接作用的草地组分多且效果持久的特点。因此,系统阐释牦牛采食特征、践踏过程和粪尿返还对土壤物理结构、主要养分动态和植被生长的影响效应,能够为加深关于放牧牦牛行为对高寒草地土壤-植被系统养分生物地球化学循环的作用过程和影响机制的认知奠定重要的理论基础,进而可为优化牦牛放牧模式、维持脆弱高寒草地生态系统可持续发展和加强青藏高原国家生态安全屏障建设等提供有益参考。     

Plant and sward response to patch grazing in the Highland Sourveld

Abstract

Selective grazing by livestock inevitably results in patch grazing. This study was initiated to determine the effects of patch grazing on (1) the vigour of a single grass species, Themeda triandra, and of the sward, and (2) sward species composition. The generally held idea that a full season's rest followed by an early spring burn would prevent preferential grazing of patch grazed areas which had developed in the seasons before the rest was also tested. The vigour of 71 triandra was estimated from etiolated growth of marked tufts while sward vigour was indexed by above‐ground herbage production (AGHP). Etiolated growth of T. triandra and AGHP of the sward within patches were negatively affected by three seasons of grazing, but a full season's rest appeared sufficient to restore both the etiolated growth of T. triandra and the AGHP of the sward to a level similar to that in the non‐patches. A full season's rest followed by spring burning did not, however, prevent preferential grazing of grazed patches which had developed in the seasons prior to the rest. Species composition within patches (characterised by Increaser II species) differed significantly from the species composition of non‐patches (characterised by Increaser I species). Patch grazing may therefore initiate the rangeland degradation process in Highland Sourveld and patch grazing may be the focus from which rangeland degradation proceeds.     

Seasonal translation of infective larvae of gastrointestinal nematodes of cattle and the effect of Duddingtonia flagrans: a 3-year pilot study

A study was conducted over 3 years (1998-2000) to investigate larval availability of gastrointestinal nematodes from faeces of cattle reared under different parasite control schemes. These cattle were part of a parallel, but separate grazing trial, and were used as donor animals for the faecal material used in this experiment. At monthly intervals, faeces were collected and pooled from three groups of first-season grazing cattle. These groups were either untreated, ivermectin bolus treated or fed the nematophagous fungus Duddingtonia flagrans. The untreated and fungus treated animals were infected with gastrointestinal nematodes and the number of eggs per gram (epg) pooled faeces ranged between 50 and 700 in the untreated group and between 25 and 525 epg in the fungus treated group. Each year between June and September, artificial 1 kg dung pats were prepared and deposited on pasture and protected from birds. The same treatments, deposition times and locations were repeated throughout the study. Larval recovery from herbage of an entire circular area surrounding the dung pats was made in a sequential fashion. This was achieved by clipping samples in replicate 1/4 sectors around the dung pats 4, 6, 8 and 10 weeks after deposition. In addition, coinciding with the usual time of livestock turn-out in early May of the following year, grass samples were taken from a circular area centred where the dung pats had been located to estimate the number of overwintered larvae, which had not been harvested during the intensive grass sampling the previous year. It was found that recovery and number of infective larvae varied considerably within and between seasons. Although the faecal egg counts in 1999 never exceeded 300 epg of the faecal pats derived from the untreated animals, the abnormally dry conditions of this year generated the highest level of overwintered larvae found on herbage in early May 2000, for the 3 years of the study. Overall, biological control with D. flagrans significantly reduced larval availability on herbage, both during and between the grazing seasons, when compared with the untreated control. However, the fungus did not significantly reduce overwintered larvae derived from early season depositions (June and July), particularly when dung pats disappeared within 2 weeks after deposition. Very low number of larvae (<3 per kg dry herbage) were sporadically recovered from grass samples surrounding the ivermectin bolus faecal pats.     

Patch grazing of Tall Grassveld by cattle after a spring burn

Patterns of herbage removal by rotationally stocked cattle (at a density of 4.85AUE ha^-1) on initially structurally homogenous Tall Grassveld were examined over a single season. Three unreplicated camps were stocked early (29 days), at the recommended '10-15cm' sward height (44 days), and late (80 days) after a spring burn. Temporal change in the spatial distribution of herbage in each treatment was described by intensive measurement of compressed sward height (CSH) with a disc pasture meter and analysed with parametric and spatial statistics. Grazing pressure at the start of the grazing was highest in the early graze, intermediate at the recommended, and least in the late graze treatment because of variation in initial herbage mass related to period of deferment after the burn. The early graze paddock was most spatially uniform and the late graze paddock the most uneven and patchy before grazing. Such initial conditions significantly affected subsequent herbage removal patterns: the greater the amount and spatial variability of herbage accumulated before grazing, the greater the chance for patches to develop through area-selective grazing. The early graze paddock was utilised non-selectively during the first two grazing periods but similar to other treatments, became patchier with time. Spatial pattern, a mosaic of short, intermediate and tall patches, peaked in late summer and was most pronounced in the late graze treatment. Intensive, early stocking after a burn is recommended for minimising intraseasonal development of patches and efficient use of high-quality forage available after a burn.     

The efficacy of formulations of triclabendazole and ivermectin in combination against liver fluke (Fasciola hepatica) and gastro-intestinal nematodes in cattle and sheep and sucking lice species in cattle

OBJECTIVE: To assess the efficacy of two formulations of triclabendazole and ivermectin in combination against liver fluke (Fasciola hepatica), gastro-intestinal nematodes and sucking louse species in cattle and sheep. PROCEDURE: A study of 540 cattle and 428 sheep at 18 sites throughout Victoria and New South Wales was undertaken. At each site, one group of cattle or sheep was treated with a combined formulation (Fasimec Cattle or Fasimec Sheep), another received ivermectin and triclabendazole separately. In trials on lice infestation, an additional group remained untreated. Samples for faecal egg counts were collected on days -7, 0 (treatment day), +7, +14 and +21 after treatment. Lice assessments were carried out on days -7, 0, +7, +14, +28, +42 and +56. RESULTS: Both treatments were highly efficacious (> 98% efficacy) against liver fluke in cattle and sheep, against three sucking lice species of cattle and against gastro-intestinal nematodes in sheep. There was also no significant difference between treatments in efficacy. Against gastro-intestinal nematodes, Fasimec Cattle was significantly (P < 0.01) more effective than the separately applied ivermectin and triclabendazole treatment. Mean efficacy for the Fasimec Cattle and Ivomec/Fasinex 120 groups respectively, was 97.6% and 94.2% on Day +7, 98.9% and 91% on Day +14 and 98.5% and 92.6% on Day +21. CONCLUSION: The efficacy of Fasimec' Cattle and Fasimec Sheep was at least equal to that of currently registered products (with the same active ingredients) used to control these parasites.     

Effects of sheep and cattle alternate grazing on sheep parasitism and production

Production of sheep (nursing ewes) grazing alternately with cattle (growing weaned heifers) was compared to the production of sheep or cattle grazing alone (controls). Pasture production and sheep parasitism were also monitored. The herbage allowance was higher for the control heifers than for the alternate heifers, but the leaf to green material ratio (LGMR) was lower, and no difference on heifer growth was revealed (443 vs. 431g.d^-1, P = 0.54). The LGMR was higher for the alternate sheep (+3 points) than for the control sheep, except during the dry season, when the herbage density was lower. The effects of parasitism on the packed cell volume of alternate ewes and lambs were lower than those of control ewes and lambs. However, the infection of sheep by Cooperia sp. (better adapted to cattle) was significantly higher for the alternate sheep than for the controls, and some indication of cattle infection by Haemonchus contortus was suggested. The 70-day lamb weight was higher in the alternate grazing system than in the control (+0.76,+1.11 and+0.61kg for the dry, intermediate and rainy seasons, respectively), and the average 70-day lamb production per ewe exposed was 21.42kg in the alternate grazing system vs. 18.59kg in the control (P = 0.003).     

Tissue residues of ractopamine and urinary excretion of ractopamine and metabolites in animals treated for 7 days with dietary ractopamine

Ractopamine HCl is a beta-adrenergic leanness-enhancing agent recently approved for use in swine. Depletion of ractopamine in tissues, and elimination of ractopamine and its metabolites in urine, is of interest for the detection of off-label use. The objectives of this study were to measure the residues of ractopamine in livers and kidneys of cattle (n = 6), sheep (n = 6), and ducks (n = 9) after treatment with dietary ractopamine for seven (sheep, ducks) or eight (cattle) consecutive days and to measure the depletion of ractopamine from urine of cattle and sheep. Two cattle and sheep and three ducks were each slaughtered with withdrawal periods of 0, 3, and 7 d. Urine samples were collected daily from cattle and sheep. Tissue ractopamine concentrations were determined using the regulatory method (FDA approved) for ractopamine in swine tissues. Ractopamine residues in urine samples were measured before and after hydrolysis of conjugates. Analysis was performed with HPLC using fluorescence detection after liquid- (hydrolyzed samples) and(or) solid-phase extraction. No residues were detected in duck tissues. Liver residues in sheep averaged 24.0 and 2.6 ppb after 0- and 3-d withdrawal periods, respectively. Sheep liver residues after a 7-d withdrawal period were less than the limit of quantification (2.5 ppb). Sheep kidney residues were 65.1 and undetectable at 0- and at 3- and 7-d, withdrawal periods, respectively. Cattle liver residues were 9.3, 2.5, and undetectable after 0-, 3-, and 7-d withdrawal periods, respectively; kidney residues were 97.5, 3.4, and undetectable at the same respective withdrawal periods. Concentrations of parent ractopamine in sheep urine were 9.8+/-3.3 ppb on withdrawal d 0 and were below the LOQ (5 ppb) beyond the 2-d withdrawal period. After the hydrolysis of conjugates, ractopamine concentrations were 5,272+/-1,361 ppb on withdrawal d 0 and 178+/-78 ppb on withdrawal d 7. Ractopamine concentrations in cattle urine ranged from 164+/-61.7 ng/mL (withdrawal d 0) to below the LOQ (50 ppb) on withdrawal d 4. After the hydrolysis of conjugates in cattle urine, ractopamine concentrations were 4,129+/-2,351 ppb (withdrawal d 0) to below the LOQ (withdrawal d 6). These data indicate that after the hydrolysis of conjugates, ractopamine should be detectable in urine of sheep as long as 7 d after the last exposure to ractopamine and as long as 5 d after withdrawal in cattle.     

Impact of grazing intensity on herbage intake, composition, and digestibility and on live weight gain of sheep on the Inner Mongolian steppe

High grazing pressure during the last decades caused severe ecological problems in the steppe of Inner Mongolia, China. The objective of the present study was to determine the effects of grazing intensity of sheep on herbage mass (HM) and intake, chemical composition and digestibility of herbage, and on live weight gain (LWG). A grazing experiment with six different grazing intensities (1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep/ha) was conducted in the growing season of 2005 in the Xilin River Basin. HM decreased from 1.5 t DM/ha at the lowest grazing intensity to 0.6 t DM/ha at the highest grazing intensity. NDF content of the herbage was high (> 700 g/kg DM) and relatively constant, whereas acid detergent lignin (ADL) content increased with grazing intensity and with proceeding grazing season. Digestibility of organic matter ingested (DOM) tended to decrease with grazing intensity as well as intake of organic matter (OMI) and of digestible organic matter (DOMI) per sheep (P = 0.090 and P = 0.065, respectively), whereas LWG per sheep decreased with increasing grazing intensity (P = 0.018). DOM and OMI were negatively related to ADL content. However, herbage intake and LWG per ha increased with grazing intensity (P < 0.001) and reached their maximum at 9 and 7.5 sheep per ha, respectively. This observation confirms the current farmers' practise of high grazing pressure ignoring long term grassland productivity and ecological problems. Therefore, the studies are continued to provide further information on long term effects. This study could show pronounced effects of grazing intensity on animal and grassland productivity and the suitability of the methods applied to measure intake and digestibility of herbage in a large scale grazing experiment with sheep.     

Spotted Knapweed Utilization by Sequential Cattle and Sheep Grazing

Prescribed (or targeted) sheep grazing can effectively suppress the invasive perennial forb spotted knapweed (Centaurea stoebe L. ssp. micranthos [Gugler] Hayek). Some ranchers and other natural resource managers, however, resist using this weed management tool over concerns that sheep may consume too much of the graminoid standing crop, thereby decreasing its availability to cattle and wildlife and possibly harming graminoids with excessive defoliation. One potential approach to address these concerns is to graze spotted knapweed infestations first with cattle, immediately followed by sheep. We evaluated this sequential grazing strategy on foothill rangeland in western Montana, comparing sequential grazing at a moderate stocking rate in mid June (spotted knapweed in bolting stage) vs. mid July (spotted knapweed in late-bud/early flowering stage). Pastures (0.81 ha) were grazed with three yearling cattle for 7 d, immediately followed with 7 d of grazing by seven yearling sheep. Combined relative (i.e., utilization) of graminoids by cattle and sheep averaged 40% in June and July, safely within sustainable grazing use levels recommended for the site. Combined relative use of spotted knapweed by cattle and sheep also did not differ between June and July, averaging 62%. Previous research indicates that this degree of use is sufficient to suppress spotted knapweed. Our results indicate that prescribed sheep grazing can be applied immediately following cattle grazing in either June or July to suppress spotted knapweed without overusing desirable graminoids. Cattle and sheep will eat less graminoids and more spotted knapweed if cattle and sheep graze sequentially when spotted knapweed is in its late-bud/early flowering stage (mid July) rather than its bolting stage (mid June).     

Tissue distribution of bovine spongiform encephalopathy infectivity in Romney sheep up to the onset of clinical disease after oral challenge

Sixty Romney sheep of three prion protein genotypes were dosed orally at six months of age with an inoculum prepared from the brains of cattle clinically affected with BSE, and 15 sheep were left undosed as controls. They were randomly assigned within genotype to groups and were sequentially euthanased and examined postmortem at intervals of six or 12 months, depending on their predicted susceptibility. Tissue pools prepared from the three, four or five dosed animals in each group were inoculated into groups of 20 RIII mice as a bioassay for infectivity. Separate inocula were prepared from the matched control sheep killed at each time. In the ARQ/ARQ sheep killed four months after inoculation, infectivity was detected in the Peyer's patch tissue pool, and at 10 months it was detected in the spleen pool; from 16 months, infectivity was detected in a range of nervous and lymphoreticular tissues, including the spinal cord pool, distal ileum excluding Peyer's patches, liver, Peyer's patches, mesenteric and prescapular lymph nodes, spleen, tonsil and cervical thymus. No infectivity was detected in the tissue pools from the ARQ/ARR and ARR/ARR sheep killed 10 months or 22 months after infection.     

Disintegration of dung pats from cattle treated with the ivermectin anthelmintic bolus, or the biocontrol agent Duddingtonia flagrans

An experiment was performed during the grazing seasons of 1998, 1999 and 2000 to study the influence of the antiparasitic drug ivermectin and the nematophagous fungus Duddingtonia flagrans on cattle dung disintegration. The faeces originated from groups of animals that were part of a separate grazing experiment where different control strategies for nematode parasite infections were investigated. Each group consisted of 10 first-season grazing cattle that were either untreated, treated with the ivermectin sustained-release bolus, or fed chlamydospores of D. flagrans. Faeces were collected monthly on 4 occasions and out of pooled faeces from each group, 4 artificial 1 kg dung pats were prepared and deposited on nylon mesh on an enclosed pasture and protected from birds. The position of the new set of pats was repeated throughout the 3 years of the study. Each year, the dung pats were weighed 4, 6, 8 and 10 weeks after deposition and immediately afterwards replaced to their initial positions. Results showed that there was no difference in faecal pat disintegration between groups. However, the time-lag between deposition and complete disintegration of the faeces varied significantly between deposition occasions. Dung pats disappeared within 2 weeks (visual observation) when subjected to heavy rainfall early after deposition, whereas an extended dry period coincided with faeces still remaining 12 months after deposition.     

Some observations on the use of the morantel sustained‐release bolus in first season‐grazing calves on a Belgian dairy cattle farm

Summary

The efficacy of the morantel sustained‐release bolus (MSRB) in controlling gastrointestinal parasites in first‐season grazing calves was evaluated on a dairy cattle farm in Belgium. The calves grazed a pasture which had been used by bolus‐treated animals in the three previous years. The effect of bolus administration was determined with respect to live weight gain, faecal egg shedding, herbage larval counts, serum pepsinogen levels and ELISA antibody titres.

In spite of an incomplete reduction of faecal egg shedding during the first months of the grazing season, bolus administration resulted in the prevention of parasitic gastro‐enteritis in the calves. A weight gain advantage of 35,2 kg of the bolus‐treated animals over the controls was noted already at two months after turnout. This weight gain advantage was maintained until housing.

The usefulness of serum pepsinogen values and ELISA antibody titres as parameters in prevention experiments is stressed. Both serological parameters gave more information concerning infection level than did the faecal egg output and the herbage larval counts.     

绵羊宿营法清除天然植被对土壤和植物的影响

研究绵羊宿营法通过践踏和粪尿对土壤和对天然植被和人工草地的影响。结果表明,绵羊啃食和践踏对植被地上部分损坏严重,8羊夜后草本植物被全部清除,但对土壤容重、紧实度和通气性无显著影响。新鲜粪尿入土后,氨态氮和亚硝态氮浓度迅速上升(最高值分别达377mg·kg^-1和56.1mg·kg^-1),对植物产生毒害作用。单纯尿处理土壤氨态氮和亚硝态氮浓度分别达139mg·kg^-1和28.1mg·kg^-1,显著高于单一粪处理和对照。无毛丑柳叶片粗蛋白质含量显著高于对照(P<0.01)。调查结果表明,羊奶果和黄花香发芽枝条数在试验前后变化不大,但宿营后的无毛丑柳枝条数显著少于处理前。宿营处理的产草量明显高于践踏处理。     

Can Sheep Control Invasive Forbs Without Compromising Efforts to Restore Native Plants?

Domestic sheep (Ovis aries) are increasingly being used to control non-native invasive plants in areas where restoration is a management goal. However, the efficacy of sheep grazing depends on both its potential for controlling undesirable plants and its ability to promote natives. To date, few studies have investigated impacts of sheep grazing on native forb recovery in North American grasslands. We assessed the impact of sheep on forbs by measuring the number of stems grazed before and after sheep foraged in western Montana, United States. Sheep grazed a higher percentage of non-native than native forbs (70% vs. 23%, respectively), and number of stems grazed was six times higher for non-natives than natives (48 vs. 5, respectively). Sheep preferentially selected the non-native forbs sulphur cinquefoil and yellow salsify over leafy spurge (fi = 2.075; fi = 0.969; fi = 0.969, respectively), as well as the native forbs white prairie aster (fi = 1.090) and blanketflower (fi = 1.000). Selection of native forbs was positively correlated with their pregrazing abundance and increased over the grazing period. Our findings indicate that when using sheep to control invasive forbs, appropriate timing and monitoring of grazing are critical for reducing nontarget impacts to native vegetation.     

放牧强度对羊氮素贮量动态变化的影响

在河北坝上鱼儿山牧场研究放牧强度对杂种公羔采食氮量、排泄氮量、沉积氮量及增重的影响。结果表明,随着放牧强度的增加,羊干物质采食量逐渐减少,同时采食氮量也相应减少,但差异不显著(P>0.05)。放牧强度对羊体沉积氮占食入氮比例的顺序为中牧>轻牧>重牧,消化氮的利用率也以中牧区最高。在轻牧与中牧区羊的日增重较快。     

Concentration of conjugated linoleic acid in grazing sheep and goat milk fat

The conjugated linoleic acid (CLA) content of grazing sheep and goat milk fat, throughout their lactation period, was examined. Six sheep and six goat representative farms were selected at random and milk samples were taken at monthly intervals for fatty acids profile determination. Sheep and goat nutrition was based on natural grazing and on supplementary feeding during the winter months. From April onwards, grazing native pastures was the only source of feed for sheep and goats. The University farm whose sheep are kept indoors all year round without any grazing, was also used as reference. Fifteen individual milk samples were also taken in April from a sheep and goat farm respectively, in order to see the variability of CLA inside the farm. The results showed that: a. the CLA content of grazing sheep and goat milk fat increased significantly in April–May (early growth stage of grass) and then declined while that of indoors kept sheep was more or less constant during the same period, b. the isomers cis-9, trans-11 and trans-10, cis-12 of CLA were found in grazing sheep milk fat, while in indoors kept sheep and goats' milk fat only the cis-9, trans-11 isomer was found, c. the CLA content of sheep milk fat was much higher than that of goats, d. a negative correlation between sheep milk fat and CLA content was found and e. there was considerable variation in milk fat CLA content between sheep and goat farms and inside the farms.     

Absence of a weight gain response to Vitamin B12 supplementation in weaned dairy heifers grazing pastures of marginal cobalt content

Aim. To obtain information on serum and liver vitamin B₁₂ and urinary methylmalonic acid concentrations as diagnostic tests to predict a weight gain response to supplementation with vitamin B₁₂ in young dairy cattle when grazing pasture of low cobalt content.

Methodology. Forty dairy cattle (12 Friesian, 14 Friesian × Jersey and 14 Jersey) were allocated to two equal sized groups, treated and untreated, based on liveweight. At monthly intervals for 14 months, all animals were weighed, their serum and urine sampled, their liver biopsied and the pasture sampled from the paddocks they were grazing and going to graze. Serum and liver were assayed for Vitamin B₁₂ concentrations. For the first 5 months of the trial, urine was assayed for methylmalonic acid concentrations. Both washed and unwashed pasture samples were assayed for cobalt concentrations.

Results. No weight gain response occurred to Vitamin B₁₂ supplementation in young growing cattle grazing pasture with a cobalt concentration of 0.04-0.06 mg/kg DM. For 5 months of the trial, liver Vitamin B₁₂ concentrations from untreated calves were in the range 75-220 nmol/kg and serum vitamin B₁₂ concentrations were as low as 72 pmol/1. There was no associated growth response to supplementation.

Conclusion. Further trials involving young cattle grazing pastures with cobalt concentrations less than 0.04 mg/kg DM are required to reliably determine liver and serum Vitamin B₁₂ concentrations at which growth responses to Vitamin B₁₂ or cobalt supplementation are likely under New Zealand pastoral grazing conditions.     

Bison Versus Cattle: Are They Ecologically Synonymous?

Historically, the plains bison (Bison bison Linnaeus) was the most numerous and influential grazer on the Great Plains. Today 500 000 bison occupy North America among more than 100 000 000 cattle. In an attempt to restore their historical ecological role, bison are translocated onto landscapes previously manipulated for cattle use through water and fence development. We hypothesized that bison would use these landscapes similarly to cattle, thus maintaining homogenous grazing and reducing the restoration potential of bison at a landscape scale. We quantified differences between bison populations at different locations and spatial scales (American Prairie Reserve, Malta, Montana, USA, and Grasslands National Park, Val Marie, Saskatchewan, Canada, 2010–2011) and bison and cattle at similar locations and spatial scales using behavioral observations, movement analyses, and resource selection functions. Bison and cattle differed in all behaviors (grazing, standing, bedded, moving, other); however, landscape attributes resulted in behavior differences within species. Cattle spent a higher proportion of time grazing (45–49%) than bison (26–28%) and increased time at water. Bison moved at a 50–99% faster rate than cattle, and first passage time movement analyses identified selection of bison foraging patches (11 690 ha) larger than cattle foraging patches (48–615 ha). Similar to cattle, bison avoided most vegetation communities in relation to riparian communities and selected areas closer to water. Cattle selected for high plant biomass, whereas bison selected for intermediate plant biomass. This study has implications when bison and cattle are used to meet prairie restoration objectives. For bison, large landscapes that include variation in topography and vegetation communities are required. Furthermore, limiting manmade water sources may facilitate bison grazing patterns that more closely approximate historical bison use. For livestock, reduced movement and increased time spent grazing encourage grazing practices that increase heterogeneous grazing at a pasture scale.     

Burning and Climate Interactions Determine Impacts of Grazing on Tallgrass Prairie Systems

Tallgrass prairie may respond differently to prescribed burning and subsequent preferential grazing, termed pyric herbivory, under variable climate conditions. This 6-yr study (2011−2016) compared tallgrass prairie pastures that were subjected to burned and unburned conditions while exposed to grazing under differing climate conditions in the Southern Great Plains of the United States. The study area consisted of six pastures, three burned and three unburned. Each burned pasture was further divided into three patches and subjected to a 3-yr rotational burning cycle. The Enhanced Vegetation Index (EVI) derived from Landsat 7/8 (EVI_LS) and Moderate Resolution Imaging Spectroradiometer (MODIS, EVI_MOD) was used to indicate vegetation production depending on size of pastures. On the basis of EVI_LS, most burned patches (11 of 18) had lesser production (overall difference of 3%) than unburned patches within the same pasture. The differences were larger (13%) in a drought yr (2011) compared with normal (3% in 2013) and wet (<1% in 2015) yrs. The distribution of precipitation controlled EVI_LS for periods during and after grazing. The burned patches tended to have lower EVI_LS during grazing periods than the unburned patches within the same pasture, probably because of selective grazing of newly grown grass in recently burned patches. In contrast, the differences in EVI_LS between during and after grazing periods were mostly (78%) smaller in burned than unburned patches. However, more variations in EVI_LS existed among pasture comparisons due to landscape heterogeneity. Similar results were observed with EVI_MOD. Overall, results demonstrated that pyric herbivory management and climate determine the impacts of grazing on tallgrass prairie systems. The contrasting seasonal forage availabilities in burned and unburned patches, indicated by different seasonality of EVI, also suggests that patch burning might better balance the quantity and quality of the grass available for cattle grazing.