Grazing Events Research Articles

Improving the accuracy of nitrous oxide emission factors estimated for hotspots within dairy-grazed farms

Nitrous oxide (N2O) emissions from dairy-grazing pastures can be dominated by large emissions from small areas (‘hotspots’) frequently used by grazing dairy cattle (i.e., water troughs and gateways). N2O emissions from these hotspots are quantified by investigating whether N2O emissions and emission factors (% of applied N emitted as N2O, EF3) from potential hotspots are different from non-hotspots. To better characterise N2O emissions from hotspots and non-hotspots of farms to understand their contributions to national agricultural greenhouse gas inventory calculations, a series of measurements were conducted during winter and spring on two NZ typical dairy farms with contrasting soil drainage (poorly versus well drained). Before measurements were taken, the soils either received a cow urine application or remained untreated. The results showed that changes in water-filled pore space (WFPS) and mineral N around water troughs and gateways, due to additional stock movements and disproportionate excreta-N deposition during previous grazing events, affected both background and total N2O emissions. But there was little impact on EF3 values (calculated using IPCC guidelines) from deposited urine between hotspot and pasture areas. These results suggest the same EF3 values can be used for both to calculate emissions from urine deposited on grazed pastures. However, these results raise concerns about higher background emission in hotspots subtracted from measured emissions from urine-N deposition in calculating EF3 values and discounting the effects of disproportionate N inputs in intensive agriculture on increased background emissions (legacy effect). This IPCC inventory method does not account for the legacy effect of N loading prior to the measurements which may underestimate the emissions. Thus, an allowance for higher hotspot background emissions could be included in the Inventory to accurately estimate total emissions from agriculture.

Agronomic performance of ten perennial ryegrass varieties on commercial grassland farms

AbstractLittle information is available on the phenotypic performance of perennial ryegrass varieties when exposed to grazing conditions on commercial grassland farms. Grass varieties are classically evaluated in mechanically defoliated plot systems which, although designed to mimic grazing conditions, do not fully capture the range of stresses or interactions that a sward is subjected to under commercial settings or over any period longer than 4 years. The evolution of technology in the form of PastureBase Ireland has led to agronomic data of individual paddocks being made available for analysis over multiple years. Data used in the current study consisted of dry matter (DM) production and ground score data across a 7-year period from ten perennial ryegrass varieties grown as monocultures in 559 paddocks on 98 commercial farms. The results demonstrated how perennial ryegrass variety is associated with a range of agronomic performance traits on commercial farms; including total and seasonal DM production, grazing DM production and number of grazing events. Varieties with the highest total DM production also had the highest spring and mid-season DM production; autumn DM production was associated with the interaction between variety and year. The highest producing variety in the study, AberGain, produced 1342 kg DM/ha/year more than the mean of all other varieties. Variety differences manifested themselves as swards aged, with some varieties increasing in total DM production while others reduced in total DM production. The current work provides a basis for the consideration of on-farm variety assessment in the composition of future variety evaluation protocols.

Grazing Rotation on Restored Rangeland as a New Tool for Medusahead Control

Intake of medusahead (Taeniatherum caput-medusae (L.) Nevski) by livestock is typically low given the poor nutritional quality of the weed, but utilization may increase through the provision of supplemental nutrients. This study compared cattle that initially grazed on a supplemented pasture (SUP) of established cool-season perennial grasses and forbs to nonsupplemented cattle that grazed only medusahead-infested rangeland (NSUP) in order to determine whether supplemental nutrients could increase use of medusahead. The quality of different forage types in the plant community and grazing events on these forage types were assessed. Supplemented animals grazed medusahead to a greater extent than NSUP animals in the medusahead-infested pastures (P = 0.003). Thus, grazing of improved pastures in close temporal proximity to grazing of medusahead-infested rangeland may represent a management tool that contributes to enhancing medusahead utilization by cattle. However, future long-term studies need to be conducted in order to examine whether medusahead use by cattle can be used as a practical, low-cost tool for medusahead management.

Analyzing the impact of grazing and short-term irrigation management on soil mechanical strength of a volcanic ash soil under different types of pastures

In southern Chile, there are over 1.3 million ha of pastures on volcanic ash soils. The climate change scenario and the need to increase yields are forcing farmers to increase irrigated surface areas. This implies an intensified soil use that must be analyzed to prevent soil degradation. Therefore, this study analyzed the impact of initial pasture defoliation (mowing and grazing) and short-term irrigation managements on soil structure dependent properties of a volcanic ash soil under different types of pastures. Field penetration resistance (PR) profiles (0–80 cm), soil water content measurements (0–10 cm) and undisturbed soil samples (0–3 cm) displayed the impact of animal trampling due to repeated loading events. Though this experiment did not determine significant interactions such as pasture x defoliation method x applied load, the early developmental stage of this experiment provided a basis for better understanding deformation processes due to animal trampling when different types of pastures are irrigated in the short-term. The plastic deformation caused by loads higher than precompression stress induced an increase in soil mechanical strength (e.g. Pc increased after the first grazing, but not after mowing), affecting the macropore volume and air permeability. The short-term effects (<2 years) showed the incipient consequences of grazing and irrigation: PR increased due to animal trampling (data dispersion: grazed> mowed plots, showing footprint formation after 8 grazing events) and the higher sum of PR in non-irrigated pastures evidenced the increase of the cohesion between particles/aggregates after drying events. Therefore, it can be expected that in the medium-term (3-4 years), animal trampling could lead to significant soil deformation and a progressive increase in soil mechanical strength near the soil surface.

Adaptive multi-paddock grazing improves water infiltration in Canadian grassland soils

The maintenance of hydrologic function on grazing lands is an important management objective to sustain forage production during low moisture supply, safeguard other ecosystem goods and services and build resilience to a warming climate. Hydrologic function can be influenced by grazing patterns, as represented by variation in the timing, intensity and frequency of livestock use. While rotational, adaptive grazing (a short-duration, multi-paddock grazing system that emphasises plant recovery between grazing events) is growing in popularity and has the potential to influence grassland hydrological processes such as water infiltration, few studies have comprehensively examined infiltration in relation to on-ranch grazing practices. We examined water infiltration in grasslands on 52 ranches (set up as matched pairs) to examine whether adaptive grazing alters water infiltration in the Great Plains of western Canada, as compared to conventional grazing management employed on neighbouring ranches. We also used producer survey information to test for the influence of ongoing nuanced grazing practices on water infiltration rates, over and above the biophysical effects of soil texture, soil bulk density and plant litter, as well as cultivation history and climate. Overall, adaptive grazing, and specifically the use of higher rest-to-grazing ratios early in the growing season (prior to August 1), led to increased water infiltration in grassland soils. Water infiltration was positively associated with increased litter mass under adaptive grazing, whereas higher bulk density (and sandier) soils were associated with decreased infiltration rates. This study highlights the potential of specialised rotational grazing systems using cattle to improve soil hydrologic function in grazed grasslands.

Preserving Colias myrmidone in European cultural landscapes: requirements for the successful development from egg to higher larval stages at a Natura 2000 site in Romania

The endangered and declining butterfly species Colias myrmidone is sensitive to land-use changes and vulnerable in its immature stages. The requirements for its larval habitats are still largely unknown, which hinders appropriate management in protected areas. We examined the relation between the larval development of C. myrmidone and environmental variables at a Natura 2000 site in Romania. Individuals that reached higher larval stages had a higher cover of litter as well as a lower cover of forbs around their host plants than individuals that died in early larval stages or as eggs. Surviving individuals had less other host plants in their surrounding and were found on larger host plants. Surviving individuals were found further away from the tip of their hosts than individuals that were lost due to grazing. The grazing regime is of particular importance to ensure the successful development of C. myrmidone from egg to higher larval stages. There seems to be a trade-off between positions at the tip of the shoot with palatable leaves and positions further down that protect against grazing. Especially sheep grazing may cause high direct mortality. The higher amount of litter around surviving larvae indicates a better survival when the grazing pressure is very low, but still present to keep the habitat open. However, occasional heavy grazing events may reduce the cover of forbs.Implications for insect conservationThe designation of the investigated Natura 2000 site offers a great opportunity to implement the insights on larval development of C. myrmidone into a management plan, which can support low-intensity grazing regimes preferably with cattle.

Controlling grazing-induced multistability in a piecewise-smooth impacting system via the time-delayed feedback control

Grazing events may create coexisting attractors and cause complex dynamics in piecewise-smooth dynamical systems. This paper studies the control of grazing-induced multistability in a soft impacting oscillator by using the time-delayed feedback control. The control switches from one of the coexisting attractors to a desired one to suppress complex dynamics near grazing events. We use path-following (continuation) techniques for non-smooth dynamical systems to investigate robustness of the controller and the parameter dependence of the controlled system. In particular, several newly developed computational methods are used, including a numerical method for analysing non-smooth delay equations and a method for calculating the Lyapunov exponents and the grazing point estimation. Numerical simulations demonstrate that the delayed feedback controller is effective, and a proper selection of the control gain and delay time can simplify the complex dynamics of the system near grazing.

Automating the analysis of fish grazing behaviour from videos using image classification and optical flow

Studying and quantifying behaviour is important to understand how animals interact with their environments. However, manually extracting and analysing behavioural data from the large volume of camera footage collected is often time consuming. Deep learning techniques have emerged as useful tools in automating the analysis of certain behaviours under controlled or laboratory conditions, but the complexities of using raw footage from the field has resulted in this technology remaining largely unexplored as a possible data analysis alternative for animals in situ. Here, we use deep learning techniques to automate the analysis of fish grazing behaviour from real-world field imagery. We collected video footage in sea grass meadows in Queensland, Australia, and trained models on a training data set of over 3000 annotations. We used a combination of dense optical flow to assess pixel movement in underwater footage, spatiotemporal filtering to increase accuracy, and deep learning algorithms to classify grazing behaviour of luderick, Girella tricuspidata . When tested on novel videos the model had not seen in training, the model correctly identified nearly all individual grazing events. Deep learning shows promise as a viable tool for determining animal behaviour from underwater videos, and with further development offers an alternative to current time-consuming manual methods of data extraction. • Deep learning and dense optical flow can automate the analysis of behaviour. • This technique has a 92% accuracy in detecting grazing behaviour events. • Using spatiotemporal filtering postprocessing significantly increases performance. • Promising results call for further study into using automation of video analysis.

Grazing Effects on Bovine-Associated and Background Fecal Indicator Bacteria Levels in Edge-of-Field Runoff

Excessive levels of fecal indicator bacteria are a major cause of water quality impairment. Grazing and its management may significantly impact bacteria concentrations; however, other sources can contribute to water quality issues both in the presence and absence of cattle, thus confounding results. In this study, we utilize Bacteroides markers to evaluate bacteria loading from cattle versus background sources in runoff from rotationally grazed and ungrazed pastures and how grazing management, timing of runoff in relation to grazing events, and stocking rate affect Bacteroides marker (AllBac and BoBac) levels and ratios and their relation to E. coli concentrations in runoff at the small watershed scale. The data suggest that the AllBac and BoBac levels were not significantly impacted by grazing management or stocking rate; however, the timing of runoff events in relation to grazing events significantly impacted the levels of these markers found in runoff. Furthermore, the BoBac/AllBac ratio confirmed that fecal contamination present in runoff when sites were destocked for over two weeks largely originated from sources other than cattle. Thus, the magnitude and proportion of cattle impacts on fecal indicator bacteria in edge-of-field runoff were dramatically reduced shortly after de-stocking. However, background sources continued to contribute significant concentrations of E. coli.

The agronomic performance of perennial ryegrass varieties evaluated as monocultures and mixtures of varying complexity under animal grazing

Perennial ryegrass varieties are evaluated in monoculture plots, but in practice are typically sown as combinations of three or more varieties. Monoculture performance is used a predictor of mixture performance, but is questionable, particularly for grazing efficiency traits that interact with the grazing animal. Two field experiments were carried out to examine the production, grazing efficiency and nutritive quality traits of varieties sown in monoculture, and their binary, ternary and quaternary mixtures. Both studies contained two diploid and two tetraploid varieties comprising of only Late heading varieties in Study 1 and combinations of Late and Intermediate heading varieties in Study 2, all managed under cattle grazing with 16 grazing events taking place over two years.Synergistic effects, defined as a higher performance above that of the component variety mean (based on their respective component monoculture performance), were observed within some mixtures for certain traits although these rarely exceeded that of the best component monocultures. Performance differences attributable to ploidy in monoculture were expressed in the mixtures but differences in the spread of heading date within a mixture had few effects. Differences in grazing efficiency between varieties were also expressed within mixtures but with no consistent evidence of a synergistic enhancement of the cattle’s willingness or ability to graze sward mixtures more effectively. Mixture performance values were within the range of the component varieties for most traits, indicating that monoculture evaluation can be used as a reliable indicator of the performance of perennial ryegrass mixtures.

Grassland Mowing Detection Using Sentinel-1 Time Series: Potential and Limitations

Grasslands encompass vast and diverse ecosystems that provide food, wildlife habitat and carbon storage. Their large range in land use intensity significantly impacts their ecological value and the balance between these goods and services. Mowing dates and frequencies are major aspects of grassland use intensity, which have an impact on their ecological value as habitats. Previous studies highlighted the feasibility of detecting mowing events based on remote sensing time series, a few of which using synthetic aperture radar (SAR) imagery. Although providing encouraging results, research on grassland mowing detection often lacks sufficient precise reference data for corroboration. The goal of the present study is to quantitatively and statistically assess the potential of Sentinel-1 C-band SAR for detecting mowing events in various agricultural grasslands, using a large and diverse reference data set collected in situ. Several mowing detection methods, based on SAR backscattering and interferometric coherence time series, were thoroughly evaluated. Results show that 54% of mowing events could be detected in hay meadows, based on coherence jumps. Grazing events were identified as a major confounding factor, as most false detections were made in pastures. Parcels with one mowing event in the summer were identified with the highest accuracy (71%). Overall, this study demonstrates that mowing events can be detected through Sentinel-1 coherence. However, the performances could probably be further enhanced by discriminating pastures beforehand and combining Sentinel-1 and Sentinel-2 data for mowing detection.

A 20 y Analysis of Weather and Management Effects on a Small White Lady's-slipper (Cypripedium candidum) Population in Manitoba

The small white lady's-slipper, Cypripedium candidum, is a rare perennial orchid with a limited distribution in Canada, occurring as isolated populations in remnant tallgrass prairie in southern Manitoba and Ontario. The species is listed as endangered in both provinces and as threatened federally. Despite its status, information on how environmental conditions and land management affect population size and persistence of this species is limited. We used 20 y of monitoring data collected for a subset of the largest population in Canada to evaluate the response of small white lady's-slipper to land management and weather. Long-term monitoring suggests the population is in decline and may not persist under the current climate and management regime. Temperature appears to regulate vegetative growth and flowering proximately. Warm temperatures early in the spring, when shoots are emerging, appear favored, but high temperatures during anthesis appear detrimental, reducing both vegetative growth and flowering. In contrast, precipitation appears to have a lag effect on growth and flowering. However, snow depth was identified as a positive influence on vegetative growth, suggesting precipitation in early spring, when shoots are emerging, is also important for above-ground growth. Some grazing appears to benefit the species presumably by reducing competition and shading, but frequent grazing may increase the risk of direct damage to individuals from cattle consumption and trampling and does not provide sufficient time for individuals to recover following grazing events. Our findings add to the knowledge of orchid conservation and management, highlighting the importance of long-term monitoring in detecting population trends in species with erratic life cycles and fluctuating populations, such as the small white lady's-slipper.

A 20 y Analysis of Weather and Management Effects on a Small White Lady's-slipper (Cypripedium candidum) Population in Manitoba

The small white lady's-slipper, Cypripedium candidum, is a rare perennial orchid with a limited distribution in Canada, occurring as isolated populations in remnant tallgrass prairie in southern Manitoba and Ontario. The species is listed as endangered in both provinces and as threatened federally. Despite its status, information on how environmental conditions and land management affect population size and persistence of this species is limited. We used 20 y of monitoring data collected for a subset of the largest population in Canada to evaluate the response of small white lady's-slipper to land management and weather. Long-term monitoring suggests the population is in decline and may not persist under the current climate and management regime. Temperature appears to regulate vegetative growth and flowering proximately. Warm temperatures early in the spring, when shoots are emerging, appear favored, but high temperatures during anthesis appear detrimental, reducing both vegetative growth and flowering. In contrast, precipitation appears to have a lag effect on growth and flowering. However, snow depth was identified as a positive influence on vegetative growth, suggesting precipitation in early spring, when shoots are emerging, is also important for above-ground growth. Some grazing appears to benefit the species presumably by reducing competition and shading, but frequent grazing may increase the risk of direct damage to individuals from cattle consumption and trampling and does not provide sufficient time for individuals to recover following grazing events. Our findings add to the knowledge of orchid conservation and management, highlighting the importance of long-term monitoring in detecting population trends in species with erratic life cycles and fluctuating populations, such as the small white lady's-slipper.

Threshold values to discriminate grazing activity of dairy cows by an uni-axial accelerometer as affected by grazing season and herbage mass

Recording grazing time is important because the time allocated for each grazing event is one of the limitations to achieving high intake levels. Grazing time can be measured via visual observation or, more recently, by devices calibrated for this purpose. The Kenz Lifecorder Plus (Suzuken Co. Ltda., Nagoya, Japan) has been used to record daily grazing time with high accuracy, but none of the previous studies have analyzed how pasture characteristics and grazing management influence the recording sensitivity of this device. Thus, the aim of this study was to evaluate the effect of pre-grazing herbage mass and season of the year on the activity level recorded by the Lifecorder Plus and its resulting threshold value used to determine a grazing event for dairy cows. A randomized 2 × 2 factorial design was used to evaluate the effect of two pre-grazing herbage masses (HM), medium herbage mass (MHM) and high herbage mass (HHM), in two seasons, winter (WIN) and spring (SPR), on the observed and predicted grazing time. In each period, two groups of six Holstein Friesian cows were fitted with a Lifecorder Plus in a collar attached to their neck. The pasture characteristics and observed and predicted grazing times were measured. There was no effect (P > 0.05) of HM on the observed grazing time. The grazing time in SPR was significantly higher (P < 0.001) than that in WIN. There was no effect (P> 0.05) of HM on the threshold value. The threshold value for SPR was significantly higher (P < 0.001) than that for WIN. The mean relative prediction error of all treatments was 0.07, which implies a precision of 0.93 in grazing detection and demonstrates a high level of precision in the estimation of daily grazing time. Determining an independent threshold value for each treatment was necessary to obtain a high degree of precision in estimating grazing time. In conclusion, changes in the structural sward characteristics caused by grazing management or the annual cycle of growth of the pasture affect both the activity level recorded using a Lifecorder Plus and the threshold value obtained to detect grazing events in dairy cows. When studies incorporate factors that might alter grazing behavior, a specific threshold value for the study conditions needs to be determined to estimate the grazing time of dairy cows with higher precision.

PSV-11 Grazing diverse combination of tanniferous and non-tanniferous legumes: Implications for foraging behavior, performance and hair cortisol in beef cattle

Abstract We tested the effect of increasingly diverse combinations of tanniferous legumes (birdsfoot trefoil-BFT, sainfoin-SF) and alfalfa (ALF) on cattle foraging behavior, performance and hair cortisol concentration. Pairs of heifers (401 ± 49.6 kg) grazed three spatial replications of seven treatments (n = 3/treatment): monocultures (BFT, SF, ALF) and all possible 2- and 3-way choices among strips of these legumes in a completely randomized block design in two 25-d periods during 2 consecutive years. The fewest grazing events occurred in BFT (42.0% of the total scans recorded; P &amp;lt; 0.10), with other treatments ranging between 47.8 (SF-BFT) and 52.6% (ALF-SF) of the total scans recorded. Heifers selected a varied diet, preferring SF over BFT or ALF in 46:27:27 and 70:30 ratios (3- and 2-way choice, respectively) and preferred BFT over ALF (62:38 ratio). All treatments followed similar daily grazing patterns (P &amp;gt;0.10), with two major grazing events (1 hour after sunrise and 3 hours before sunset). No differences among treatments were observed for the number of steps taken, motion index, or percentage of time spent standing (1,600, 5,356, and 45.3%, respectively; P &amp;gt;0.10), suggesting that heifers in choice treatments did not invest extra time in walking, searching or patch-switching activities relative to monoculture treatments. Heifers in the 3-way choice gained more BW (1.27 Kg/d) than in monocultures (1.00 kg/d; P = 0.014), or 2-way choices (0.97 kg/d; P = 0.007), suggesting nutritional synergism among legumes in the treatment of greatest diversity. No differences in hair cortisol concentration were observed among treatments, with values ranging between 1.40 (BFT) and 2.12 ng/g (3-way choice) (P &amp;gt;0.10). Thus, forage diversity enhanced animal performance, likely driven by interactions among condensed tannins and dietary protein, without affecting hair cortisol levels or grazing efficiency, explained by the spatial arrangement (strips) of the forage species presented.

76 Evaluating Nitrogen Management Strategies to Improve Southern Bermudagrass Grazing Systems

Abstract Bermudagrass (Cynodon dactylon) is one of the most common perennial warm-season forage crops grown in the South. While prominent in the region bermudagrass management requires large amounts of fertility and forage quality is moderate at best. Incorporating a legume into bermudagrass pastures could serve as an alternative to the necessary applications of synthetic N, while also improving the nutritive value of the forage base. A two-year grazing evaluation was conducted from May-Sept. 2018 (Y1) and May-Aug. 2019 (Y2) at the University of Georgia Tifton Campus in Tifton, Georgia, to compare concurring production of alfalfa/bermudagrass mixed pastures (BGA) with bermudagrass monoculture pastures with (BGN) or without (BGZ) the application of synthetic nitrogen. The experimental design was a randomized complete block with three treatments and two replications. All paddocks were evaluated pre and post grazing event for herbage availability, botanical composition, forage species competitiveness, and nutritive value. Paddocks (0.8-ha) were rotationally grazed using put and take management with stocker steers (Y1 BW=195.9±22.9 kg; Y2 BW=228.5±30.0 kg), two testers per treatment. Steers were weighed at initiation, conclusion, and on a 28–30 day interval for calculation of ADG and gain/ha. Statistical analysis was conducted using the PROC MIXED procedure of SAS. Despite significant drought in Y2, year did not affect total gain/ha, however treatment did (P = 0.04), such that BGA was highest (383.6±35.1 kg/ha), and BGN and BGZ were not different (261.2±35.1 kg/ha and 239.0±35.1 kg/ha, respectively). This is likely due to the lower stocking density and inclusion of high-quality volunteer annual grasses in BGZ treatments which allowed for selective grazing. These data suggest that rotationally grazing alfalfa/bermudagrass mixtures can result in a higher gain/ha, than bermudagrass pastures that are supplemented with or without synthetic N in the South.

77 Evaluating Nitrogen Management Strategies to Improve Southern Bermudagrass Grazing Systems

Abstract Bermudagrass (Cynodon dactylon) is one of the most common perennial warm-season forage crops grown in the South. While prominent in the region bermudagrass management requires large amounts of fertility and forage quality is moderate at best. Incorporating a legume into bermudagrass pastures could serve as an alternative to the necessary applications of synthetic N, while also improving the nutritive value of the forage base. A two-year grazing evaluation was conducted from May-Sept. 2018 (Y1) and May-Aug. 2019 (Y2) at the University of Georgia Tifton Campus in Tifton, Georgia, to compare concurring production of alfalfa/bermudagrass mixed pastures (BGA) with bermudagrass monoculture pastures with (BGN) or without (BGZ) the application of synthetic nitrogen. The experimental design was a randomized complete block with three treatments and two replications. All paddocks were evaluated pre and post grazing event for herbage availability, botanical composition, forage species competitiveness, and nutritive value. Paddocks (0.8-ha) were rotationally grazed using put and take management with stocker steers (Y1 BW=195.9±22.9 kg; Y2 BW=228.5±30.0 kg), two testers per treatment. Steers were weighed at initiation, conclusion, and on a 28–30 day interval for calculation of ADG and gain/ha. Statistical analysis was conducted using the PROC MIXED procedure of SAS. Despite significant drought in Y2, year did not affect total gain/ha; however, treatment did (P = 0.04), such that BGA was highest (383.6±35.1 kg/ha), and BGN and BGZ were not different (261.2±35.1 kg/ha and 239.0±35.1 kg/ha, respectively). This is likely due to the lower stocking density and inclusion of high-quality volunteer annual grasses in BGZ treatments which allowed for selective grazing. These data suggest that rotationally grazing alfalfa/bermudagrass mixtures can result in a higher gain/ha, than bermudagrass pastures that are supplemented with or without synthetic N in the South.

Impact of pasture height and herbage mass on suppression of variegated thistle in North Island East Coast hill country

Variegated thistle in East Coast North Island hill country reduces pasture and livestock productivity. To quantify the impact of increasing amounts of pasture cover (herbage mass) on this weed, variegated thistle seeds were hand-sown in autumn into pasture swards that ranged in height from 0 cm (bare ground) to 12 cm, on an East Coast property near Gisborne. Sward height was maintained by mowing without damaging the thistle plants. Increasing pasture cover reduced thistle emergence, height, diameter, biomass, survival, and seed production. By early June, 7 weeks after sowing, thistle emergence was greatest from bare ground and from maintaining a pasture at a height of 3 cm (&gt;1100 kg DM ha-1 in autumn) and declined with increasing pasture height. By December, thistle height, diameter, biomass, flowerhead production and survival were highest in the bare ground treatment (thistle biomass ≈760 g plant-1), much lower in the 3-cm pasture height treatment (≈20 g plant-1), negligible in the 6-cm (&gt;1600 kg DM/ha) and nil in the 8-cm (&gt;1800 kg DM ha-1) and 12-cm (&gt;2700 kg DM ha-1) pasture treatments (P&lt;0.002). Maintaining pasture height of 3 cm severely reduced variegated thistle establishment, growth and flowerhead production. Results infer that grazing management strategies, such as lengthening the interval between grazing events in autumn and early winter, will increase pasture cover and are likely to severely reduce thistle establishment, growth and seed production.

Predation of livestock by puma (Puma concolor) and culpeo fox (Lycalopex culpaeus): numeric and economic perspectives

Predation on livestock by wild carnivores represent large economic losses worldwide. Livestock predation by puma (Puma concolor) and culpeo fox (Lycalopex culpaeus) represents not only a problem for the Sajama National Park (SNP) management in Bolivian highlands, but also for the conservation efforts of these predators. At SNP we quantified: 1) The frequency of attacks by puma and culpeo fox on domestic livestock. 2) The effect of socio-ecological variables on the predation of livestock by these predators. 3) Estimated the losses of livestock due to other causes and compared these with the losses resulting from predation. We expected that the probability of a carnivore attack on a ranch would increase with higher livestock densities, lower abundance of wild prey, good habitat characteristics for carnivores, and low rates of husbandry and would decrease in smaller ranches and/or in areas near human settlements. We monitored predation and other causes of livestock mortality in 33 ranches for one year and estimated biomass of livestock and wild prey and monetary losses. Predators killed 183 livestock (2.3 ± 0.9 % of the animals/ranch) equivalent to $4,215 USD and averaging 21.8 ± 19.6 % of a family’s annual income. Another 354 domestic animals died of causes unrelated to predation (201 adults and 153 yearlings), averaging 4.3 ± 4.5 % of livestock holdings per ranch. The probability of puma attacks increased with ranch size, livestock biomass and distance to the nearest town but decreased with husbandry during the dry season, while their frequency increased with ranch area. The probability of fox attacks decreased with Bofedal area, livestock biomass and better husbandry during the dry season, whereas their frequency increased when wildlife biomass decreased. Although the losses due to predation were low, the impact on the herders’ economy was important. Stock mortality resulting from malnutrition, diseases, and accidents was twice as high as through predation. To reduce losses due to livestock predation and diseases, we advocate managing livestock by reducing group numbers, providing better veterinary assistance, increasing surveillance of herds during grazing events –especially during the rainy season– and through an adequate management of young animals in corrals.

An investigation into the grazing efficiency of perennial ryegrass varieties

AbstractThe objective of this study was to compare the grazing efficiency of 30 perennial ryegrass varieties, differing in ploidy and heading date. Plots were grazed by lactating dairy cows and managed under a rotational grazing system with 19 grazing events occurring over two years. Pre‐grazing and post‐grazing compressed sward heights were measured with a rising plate meter. A mixed model was used to predict the post‐grazing sward height of each variety based on year, grazing event, block and pre‐grazing sward height. Residual grazed height (RGH) was derived as the difference between the actual and predicted post‐grazing sward height and was used as the measure of grazing efficiency. Negative RGH values indicated that the actual herbage removed was greater than that predicted and so indicated a superior grazing efficiency. Varieties differed in their level of grazing efficiency (p &lt; .001), with RGH values ranging from −0.38 to +0.34 cm. Tetraploid varieties exhibited significantly greater grazing efficiency performance than diploids (p &lt; .001), with average RGH values of −0.13 and +0.13 cm respectively. A significant difference in grazing efficiency was found among recommended perennial ryegrass varieties that are not being recorded by mechanically harvested simulated grazing protocols. A variety reappraisal that included grazing efficiency could identify varieties capable of improving on‐farm livestock productivity from grass.