Grazing Treatments Research Articles

Grazing greatly reduces the temporal stability of soil cellulolytic fungal community in a steppe on the Tibetan Plateau

Excessive livestock grazing degrades grasslands ecosystem stability and sustainability by reducing soil organic matter and plant productivity. However, the effects of grazing on soil cellulolytic fungi, an important indicator of the degradation process for soil organic matter, remain less well understood. Using T-RFLP and sequencing methods, we investigated the effects of grazing on the temporal changes of cellulolytic fungal abundance and community structure in dry steppe soils during the growing months from May to September, on the Tibetan Plateau using T-RFLP and sequencing methods. The results demonstrated that the abundance of soil cellulolytic fungi under grazing treatment changed significantly from month to month, and was positively correlated with dissolved organic carbon (DOC) and soil temperature, but negatively correlated with soil pH. Contrastingly, cellulolytic fungal abundance did not change within the fencing treatment (ungrazed conditions). Cellulolytic fungal community structure changed significantly in the growing months in grazed soils, but did not change in fenced soils. Grazing played a key role in determining the community structure of soil cellulolytic fungi by explaining 8.1% of the variation, while pH and DOC explained 4.1% and 4.0%, respectively. Phylogenetically, the cellulolytic fungi were primarily affiliated with Ascomycota (69.65% in relative abundance) and Basidiomycota (30.35%). Therefore, grazing substantially reduced the stability of soil cellulolytic fungal abundance and community structure, as compared with the fencing treatment. Our finding provides a new insight into the responses of organic matter-decomposing microbes for grassland managements.

Wounding response in Porifera (sponges) activates ancestral signaling cascades involved in animal healing, regeneration, and cancer

Upon injury, the homeostatic balance that ensures tissue function is disrupted. Wound-induced signaling triggers the recovery of tissue integrity and offers a context to understand the molecular mechanisms for restoring tissue homeostasis upon disturbances. Marine sessile animals are particularly vulnerable to chronic wounds caused by grazers that can compromise prey’s health. Yet, in comparison to other stressors like warming or acidification, we know little on how marine animals respond to grazing. Marine sponges (Phylum Porifera) are among the earliest-diverging animals and play key roles in the ecosystem; but they remain largely understudied. Here, we investigated the transcriptomic responses to injury caused by a specialist spongivorous opisthobranch (i.e., grazing treatment) or by clipping with a scalpel (i.e., mechanical damage treatment), in comparison to control sponges. We collected samples 3 h, 1 d, and 6 d post-treatment for differential gene expression analysis on RNA-seq data. Both grazing and mechanical damage activated a similar transcriptomic response, including a clotting-like cascade (e.g., with genes annotated as transglutaminases, metalloproteases, and integrins), calcium signaling, and Wnt and mitogen-activated protein kinase signaling pathways. Wound-induced gene expression signature in sponges resembles the initial steps of whole-body regeneration in other animals. Also, the set of genes responding to wounding in sponges included putative orthologs of cancer-related human genes. Further insights can be gained from taking sponge wound healing as an experimental system to understand how ancient genes and regulatory networks determine healthy animal tissues.

Climate variability supersedes grazing to determine the anatomy and physiology of a dominant grassland species

Grassland ecosystems are historically shaped by climate, fire, and grazing which are essential ecological drivers. These grassland drivers influence morphology and productivity of grasses via physiological processes, resulting in unique water and carbon-use strategies among species and populations. Leaf-level physiological responses in plants are constrained by the underlying anatomy, previously shown to reflect patterns of carbon assimilation and water-use in leaf tissues. However, the magnitude to which anatomy and physiology are impacted by grassland drivers remains unstudied. To address this knowledge gap, we sampled from three locations along a latitudinal gradient in the mesic grassland region of the central Great Plains, USA during the 2018 (drier) and 2019 (wetter) growing seasons. We measured annual biomass and forage quality at the plot level, while collecting physiological and anatomical traits at the leaf-level in cattle grazed and ungrazed locations at each site. Effects of ambient drought conditions superseded local grazing treatments and reduced carbon assimilation and total productivity in A. gerardii. Leaf-level anatomical traits, particularly those associated with water-use, varied within and across locations and between years. Specifically, xylem area increased when water was more available (2019), while xylem resistance to cavitation was observed to increase in the drier growing season (2018). Our results highlight the importance of multi-year studies in natural systems and how trait plasticity can serve as vital tool and offer insight to understanding future grassland responses from climate change as climate played a stronger role than grazing in shaping leaf physiology and anatomy.

Similar grazing mechanisms explain contrasting intake and sward-height dynamics under different grazing management

Context Average sward height has traditionally been used as a grazing management variable. However, such approach ignores the spatio-temporal heterogeneity of swards. Because the intake rate responds non-linearly to average height at plant level, we expected that sheep exposed to contrasting grazing methods with similar average heights would behave differently. Aims We hypothesised that low-intensity, high-frequency grazing results in a higher daily intake rate than does high-intensity, low-frequency grazing, despite both methods having similar average sward heights over space and time. Also, we asked whether sheep exhibit the same foraging mechanisms for a given instantaneous sward state regardless of long-term grazing conditions imposed. Methods We exposed sheep to two contrasting grazing methods with similar average height; low-intensity, high-frequency (LIHF), and high-intensity, low-frequency (HILF). We then evaluated their foraging behaviour using continuous bite-monitoring paired with detailed sward measurements during grazing down. Key results Sward height decreased markedly during the grazing period in both treatments, but the sward height depletion was faster under HILF (7.5 cm and 20.3 cm for LIHF and HILF), which means that sward structure was severely disrupted. The animals exhibited markedly different herbage intake patterns between the grazing methods, with sheep under LIHF presenting greater total daily herbage intake (850 vs 630 g DM per individual). Also, sheep demonstrated a more stable and higher instantaneous intake rate in the LIHF. Despite the difference in total daily herbage intake, the grazing treatments did not affect the behavioural mechanisms beyond their indirect effects on the rate of change in the instantaneous sward conditions. Grazing treatments created different patterns of sward change and intake rate over time, but the local and instantaneous sward conditions determined intake rate regardless of the grazing method. Conclusions Intake responses of sheep differed between grazing methods with similar average height due to sward heterogeneity over time and space. Grazing mechanisms were not directly affected by the treatments but were influenced by the sward heterogeneity imposed by the grazing management. Implications Grazing management requires not only consideration of the average sward height, but also an understanding of how the resource is distributed in time and space.

Impacts of winter grazing on soil health in southeastern cropping systems

AbstractCoastal Plain soils are often characterized by low soil organic carbon (SOC) as a result of natural and anthropogenic factors. A rotation of cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) under conventional tillage is typical in this region, but an opportunity to increase SOC and improve soil health by incorporating winter grazing of cover crops exists for producers with row crop and livestock operations. A study to assess winter grazing impacts on soil health was established in the U.S. Coastal Plain. Three cattle removal dates and an ungrazed control were evaluated for impacts on selected soil health indicators: SOC, permanganate oxidizable carbon (POXC), water stable aggregates (WSA), penetration resistance (PR), microbial biomass C (MBC), and arbuscular mycorrhizal fungi (AMF) colonization rates. After two years, MBC was highest in the control treatments, likely due to greater cover crop biomass on the soil surface at termination. No differences were observed between treatments for SOC, POXC, WSA, PR, or AMF. Increased cotton lint yield was observed in control and mid‐February treatments in 2019, likely due to greater cover crop residues on the soil surface following grazing, which may have conserved soil moisture during the growing season. Peanut yields were unaffected by treatments in 2020. Lack of differences in soil health indicators suggests that integrating winter‐grazing livestock does not negatively nor positively impact selected dynamic soil properties in the short‐term, but more time under grazing treatments is needed to thoroughly evaluate how winter‐grazing livestock impacts soil health and crop yield.

内蒙古典型草原不同地形单元放牧对土壤微生物量磷及磷酸酶活性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 内蒙古典型草原不同地形单元放牧对土壤微生物量磷及磷酸酶活性的影响 DOI: 10.5846/stxb202102200477 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金应急项目（21025120） Effect of grazing on soil microbial biomass phosphorus and phosphatase activities on different topographic unit of a typical steppe Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤微生物量磷和磷酸酶在土壤磷的有效化过程中起着极为重要的作用。过度放牧干扰微生物主导的草原土壤磷的有效化过程，地形也会驱动土壤磷的形态转化和积累。然而，地形与放牧强度的交互作用对土壤微生物参与磷活化过程的影响尚不明确，它们对不同地形单元放牧强度的响应可能存在差异。基于十年定位不同地形单元（坡地和平地）放牧试验，研究不同地形单元放牧对土壤磷酸酶活性和微生物量磷（SMBP）的影响。结果表明，地形而不是放牧显著影响土壤全磷（TP）、有机磷（PO）、有效磷（Olsen-P）含量。坡地SMBP含量显著低于平地，平地重牧（G7.5-G9.0）显著提高了SMBP含量，而坡地放牧则对其没有显著影响。土壤碱性磷酸酶（ALP）和磷酸二酯酶（PD）活性的变化只受放牧影响，而酸性磷酸酶活性（ACP）受地形驱动。平地土壤PD、ALP活性与土壤理化性质间存在复杂的联系，且与放牧强度呈负相关关系，而坡地则只保留了土壤PD活性与磷、全氮（TN）的联系。平地和坡地的土壤ACP活性与土壤化学性质无关。土壤含水量（WC）驱动了平地和坡地SMBP和磷酸酶活性的差异，其中WC、PO、TP、TN驱动平地土壤变化，而坡地土壤则受到WC、PO、TOC的影响。综上，地形驱动SMBP和土壤磷酸酶活性对放牧的响应。本研究表明在平地放牧和坡地放牧是通过不同的方式影响的微生物活化磷的过程，并且土壤含水量起到关键作用。 Abstract:Overgrazing interferes the grassland soil process of phosphorus (P) availability which is dominated by microorganisms, and topography also drives the P transformation and accumulation in soil. Soil microbial biomass phosphorus (SMBP) and enzymes involved phosphorus mineralization played important roles in soil P transformation. However, the effect of the interaction between topography and grazing rate on the participation of soil microorganisms in phosphorus activation process is not clear. In this study, the effects of grazing on the activities of soil alkaline phosphatase (ALP), acid phosphatase (ACP), phosphodiesterase (PD), and SMBP were investigated based on a ten-year grazing experiment (0, 1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 sheep/hm2) on two topography treatments (slope and flat). This study hypothesized that 1) due to the soil water content (WC) of slope treatment is lower than the flat treatment, and so do soil nutrient properties, so the effect of slope treatment on SMBP is stronger than flat soil; 2) due to the slope soil lack of phosphorus than flat soil, so the activities of ALP, ACP, PD are higher than flat soil; 3) slope soil is facing higher nutrient limit caused by the difference of parent material, and water limit caused by topography, so, there may be different environmental factor driving the change of SMBP and enzymes. The results showed that topography, not grazing, significantly affected soil TP, PO and Olsen-P. SMBP in slope treatment was significantly lower than that in flat treatment. SMBP was significantly increased by heavy grazing on flat treatment, but not on slope treatment. ALP and PD activities were only affected by grazing, while the activities of ACP were driven by topography. There was a complex relationship between the activities of PD, ALP and soil physical and chemical properties in the flat group, and there was a negative correlation between the activities of PD, ALP and grazing rate, while only the relationship between PD activities, phosphorus and TN was maintained in the slope group. The ACP activity of flat group and slope group was not related to soil chemical properties. Soil water content drives the difference between flat land and sloping land. Considering topographic factors, soil water content, PO, TP and TN drive the change of flat soil, while slope soil is affected by soil water content, PO and TOC. In conclusion, topography drives the response of SMBP phosphorus and phosphatase activity to grazing. This article indicates that, under grazing, the process of soil microorganism activities phosphorus is affected by different factors on flat and slope grazing treatments, and soil water content plays an important role. 参考文献 相似文献 引证文献

Evaluation of Grazing Options During Summer for Growing Heifers – Year 2

Developing methods to provide high quality forage through most of the year is important for cattle operations. The purpose of this study was to determine forage management options to offset the summer “slump” with fescue. Four grass pasture treatments (10 pastures total; 4 acres each) were used in a completely randomized design and stocked with growing heifers (n = 49; initial wt 473 ± 60 lb). Pasture treatments consisted of novel fescue (FES), crabgrass (CRAB), bermudagrass (BERM), and sorghum-sudan interseeded into novel fescue (SS-FES). Heifers were weighed and grazed pastures from April to September (153 d). Heifers on FES were continuously grazed. All other pastures were rotationally grazed. Sorghum-sudan was interseeded into fescue pastures in May. Average daily gain (ADG) for the entire grazing period was not different between pasture systems. In contrast to the previous year, there were no differences in heifer gain, ADG, or gain per acre for any of the grazing treatments.

Ruminating on the science of carbon ranching

Abstract There is interest in reducing CO2 concentrations in the atmosphere by managing livestock grazing to increase carbon (C) storage in soil. However, our understanding of the value of this practice of ‘C ranching’ is based on studies suffering substantial, overlooked methodological problems. We reviewed research into effects of grazing treatments on soil organic carbon (SOC) stocks (mass SOC × area₋1). We show the empirical basis for C ranching (C offset) projects relies mainly on studies with unrealistic and overly simplistic livestock grazing treatments (e.g. grazed vs. not grazed), suboptimal experimental designs (e.g. lack pretreatment data, low number of treatment replications) and problematic SOC stock metrics. Synthesis and applications. It is not clear that grazing treatments differ enough in their effects on soil organic carbon (SOC) stocks to reliably offset CO2 generated by human activities and/or reduce CO2 concentrations in the atmosphere. Therefore, we caution against overselling the value of carbon (C) ranching. Knowledge of C ranching effects on SOC is inadequate to justify C offset projects that provide ranchers with payment for environmental services. To better quantify benefits of C ranching, we advise using current best practices and expanding C ranching research with more realistic treatments over either broader spatio‐temporal scales and/or climate change treatments (e.g. drought, warming, elevated CO2).

Restoration of Degraded Grassland Significantly Improves Water Storage in Alpine Grasslands in the Qinghai-Tibet Plateau.

Alpine grassland has very important water conservation function. Grassland degradation seriously affects the water conservation function; moreover, there is little understanding of the change of water state during grassland restoration. Our study aims to bridge this gap and improve our understanding of changes in soil moisture during the restoration process. In this study, the water storage, vegetation, and meteorology of a non-degradation grassland (grazing intensity of 7.5 sheep/ha) and a severely degraded grassland (grazing intensity of 12–18 sheep/ha) were monitored in the Qinghai-Tibet Plateau for seven consecutive years. We used correlation, stepwise regression, and the boosted regression trees (BRT) model analyses, five environmental factors were considered to be the most important factors affecting water storage. The severely degraded grassland recovered by light grazing treatment for 7 years, with increases in biomass, litter, and vegetation cover, and a soil-water storage capacity 41.9% higher in 2018 compared to that in 2012. This increase in soil-water storage was primarily due to the increase in surface soil moisture content. The key factors that influenced water storage were listed in a decreasing order: air temperature, litter, soil heat flux, precipitation, and wind speed. Their percentage contributions to soil-water storage were 50.52, 24.02, 10.86, 7.82, and 6.77%, respectively. Current and future climate change threatens soil-water conservation in alpine grasslands; however, grassland restoration is an effective solution to improve the soil-water retention capacity in degraded grassland soils.

Do Bush Control Techniques Have an Effect on the Density, Cover and Recruitment of Woody Plants in a Semi-Arid Savanna? The Case of a Semi-Arid Savanna, Southern Ethiopia

High bush density and cover have negative effects on the environment in general and on livestock production, in particular in savanna rangelands. The study examined the effects of bush control techniques on woody sapling recruitment in the low land savanna region. The study consisted of 21 plots located next to each other on an area of 5.3 ha encroached byAcacia melliferaandAcacia reficienstrees. Seven bush control treatments were assigned randomly to the plots and replicated three times. In the bush clearing plot, woody species were removed at ground level using a handsaw. In the tree thinning; thinning and grazing; thinning and browsing; thinning and fire, and thinning with fire-browsing treatments, trees were thinned to the equivalents of 60% of the density of that of the control plot. Positive changes in sapling densities were observed in the clearing, thinning, and thinning and grazing treatments. In contrast, the control, thinning and browsing, and thinning and fire treatments presented negative changes in densities. A change in sapling density was highest in the cleared plot, whereas it was lowest in the thinning, fire, and browsing treatment. The correlation between changes in sapling densities and new recruitments was highly (p < 0.001) significant in the clearing, thinning, and thinning and grazing treatments thus increased sapling recruitment with the proportion greater for the clearing treatment. The significant correlation induced average sapling recruitment in the control, and low in the thinning with browsing and thinning with fire treatments. The relationship was insignificant in the thinning, fire, and browsing combination treatment and resulted in the lowest rate of saplings’ recruitment. Postthinning techniques reduced woody tree recruitment and would sustain open savanna under the continuous management plan.

Quantifying the immediate response of the soil microbial community to different grazing intensities on irrigated pastures

Grazing is known to affect soil microbial communities, nutrient cycling, and forage quantity and quality over time. However, a paucity of information exists for the immediate changes in the soil physicochemical and microbial environment in response to different grazing strategies. Soil microbes drive nutrient cycling and are involved in plant-soil-microbe relationships, making them potentially vulnerable to plant-driven changes in the soil environment caused by grazing. To test the hypothesis that variable grazing intensities modulate immediate effects on the soil microbial community, we conducted a grazing trial of three management approaches; high-intensity, short-duration grazing (HDG), low-intensity, medium-duration grazing (LDG), and no grazing (NG). Soil and vegetation samples were collected before grazing and 24h, 1 week, and 4 weeks after HDG grazing ended. Soil labile carbon (C) and nitrogen (N) pools, vegetation biomass, and soil microbial diversity and functional traits were determined, including extracellular enzymatic assays and high-throughput sequencing of the bacterial 16S rRNA and fungal ITS2 regions. We found that labile soil C and inorganic N increased following LDG grazing while C-cycling extracellular enzymatic activities increased in response to HDG grazing but both total extracellular enzymatic activity profiles and soil abiotic profiles were mostly affected by temporal fluxes. The soil fungal community composition was strongly affected by the interaction of sampling time and grazing treatment, while the soil bacterial community composition was largely affected by sampling time with a lesser impact from grazing treatment. We identified several key fungal taxa that may influence immediate responses to grazing and modulate plant-soil-microbe interactions. There was strong evidence of temporal influences on soil biogeochemical variables and the soil microbiome, even within our narrow sampling scheme. Our results indicate that the soil ecosystem is dynamic and responsive to different grazing strategies within very short time scales, showing the need for further research to understand plant-soil-microbe interactions and how these feedback mechanisms can inform sustainable land management.

UAV−Enabled Quantification of Grazing-Induced Changes in Uniformity of Green Cover on Semiarid and Mesic Grasslands

Coverage of living (green) vegetation influences rangeland processes and biodiversity but remains a challenge to quantify at small spatial grain. We describe a technique for rapid airborne (unmanned aerial vehicle) measurements of continuous spatial coverage of living vegetation at a resolution (spatial grain) of 8 cm ground sampling distance. We then applied this technique at the pasture (paddock) scale (tens of hectares) in two contrasting grassland ecosystems (semiarid shortgrass steppe in northeastern Colorado, United States and mesic grassland in central Texas, United States) to determine effects of locally relevant grazing treatments on spatial variability and dependence (pattern) in fractional coverage of green vegetation (fractional vegetation cover; FVC). Site-specific regression models developed using reflectance in visible and near-infrared wavebands explained 90% and 89% of variance in FVC for semiarid and mesic grassland, respectively. Mean FVC was similar among shortgrass steppe pastures differing in grazing treatment (light or heavy grazing by cattle, moderate cattle grazing with prairie dogs present). In contrast, FVC was lower with rotational compared with continuous, year-long grazing in the mesic grassland. Heavy grazing in shortgrass steppe and rotational grazing in mesic grassland increased the spatial uniformity in FVC by reducing spatial variability and increasing spatial dependence in FVC, the latter by increasing the similarity in FVC values among spatially separated patches. Unmanned aerial vehicle−enabled remote sensing provides for FVC at sufficiently small spatial grain to characterize spatial variation in FVC at the pasture scale. Results can be used to evaluate the effectiveness of management actions intended to alter spatial variation in FVC to achieve conservation or diversity objectives. Enhanced capacity to monitor FVC at small spatial grain promotes adaptive management of grasslands.

Mixed‐Prairie Well Site Reclamation with Natural Recovery, Seeding, and Grazing

Reclamation of surface disturbances on grasslands is an important management issue. This research examined how cattle grazing and revegetation treatments influenced vegetation development on mixed-prairie well sites. Three seed mix treatments, dominant wheatgrass (a Triticeae tribe) (four species providing 95% wheatgrass seed in the seed mix), nondominant wheatgrass (five species with 80% nonwheatgrasses in the seed mix), and diverse (22 grass and forb species), plus a natural recovery (unseeded) treatment, with and without cattle grazing, were compared with undisturbed (control) prairie for soil seedbank, vegetation composition, ground cover, and biomass. The nondominant wheatgrass seed mix resulted in communities dominated by wheatgrass species, whereas natural recovery was dominated by early and midseral species. Seeding yielded greater aboveground biomass with < 20% bare ground; natural recovery biomass was slightly less with greater bare ground (grazed 45%, ungrazed 23%). Cattle grazing reduced cover of northern wheatgrass (Elymus lanceolatus [Scribn. & J.G.Sm.] Gould) in seeded treatments. Species richness and diversity were greater with natural recovery than with seeding and in undisturbed prairie. Multivariate tests showed that plant community composition in undisturbed prairie and natural recovery differed from seeded treatments; natural recovery was dominated by early to midsuccessional species. The short-term patterns of change in different vegetation parameters suggest that irrespective of grazing, natural recovery and seeding with a diverse native seed mix could be effective approaches for mixed-prairie reclamation.

Pasture-Scale Evaluation of Postemergence Applications of Aminopyralid for Controlling Medusahead (Taeniatherum caput-medusae)

The exotic annual grass medusahead (Taeniatherum caput-medusae [L.] Nevski) has invaded millions of hectares in the western United States. The herbicide aminopyralid is an emerging tool for controlling medusahead. Aminopyralid reduces viability of grass seeds when applied just before seed production. In annual grasslands, desirable forage grasses generally begin seed production before medusahead, and applying aminopyralid when medusahead is still mostly vegetative but forage grasses have begun producing seed allows medusahead to be targeted somewhat selectively. In recent experiments, this approach reduced medusahead viability and cover to near zero and increased forage grasses. These experiments occurred in small plots, and results may differ in pastures if grazing or environmental heterogeneity causes plant stages to vary. Moreover, the results may prove highly sensitive to application timing. To address these information gaps, we factorially combined grazing and aminopyralid treatments in pastures and varied application timings in small plots. In pastures, aminopyralid reduced medusahead cover from about 45% to 20% one yr and from 60% to 20% another year. These reductions are smaller than in past research, but this doesn't seem attributed to the larger treatment area because reductions were similar in pastures and small plots treated the same time. Despite smaller reductions in medusahead cover, forage grasses increased as much or more than previously, perhaps because aminopyralid previously more sharply reduced forage grass seed viability. Seed viability did not vary with grazing, indicating grazing can occur during treatment, because aminopyralid does not have grazing restrictions. Careful application timing is critical: Just 12 d separated the least (jointing and boot stages) and most (boot to early heading) effective timings for controlling medusahead. A low rate of aminopyralid (22% of maximum labeled rate) is needed to reduce medusahead seed production, and the low cost of the low rate should encourage repeated applications when necessary.

The effect of Holstein-Friesian, Jersey × Holstein-Friesian, and Norwegian Red × (Jersey × Holstein-Friesian) cows on dry matter intake and production efficiencies in pasture-based systems

The objective of this study was to investigate the effect of cow genotype and parity on dry matter intake (DMI) and production efficiencies in pasture-based systems. Three dairy cow genotypes were evaluated over 3 yr; 40 Holstein-Friesian (HF), 40 Jersey × HF (JEX), and 40 Norwegian Red × JEX (3WAY) each year, with each genotype grazed in equal numbers on 1 of 4 grazing treatments in a 2 × 2 factorial arrangement of treatments [diploid or tetraploid perennial ryegrass (Lolium perenne L.) with or without white clover (Trifolium repens L.)]. A total of 208 individual cows were used during the experiment. The effect of parity (lactation 1, 2, and 3+) was also evaluated. Individual DMI was estimated 8 times during the study, 3 times in 2015 and in 2017, and twice in 2016, using the n-alkane technique. Days in milk at each DMI measurement period were 64, 110, and 189, corresponding to spring, summer, and autumn. Measures of milk production efficiency calculated were total DMI/100 kg of body weight (BW), milk solids (kg fat + protein; MSo)/100 kg of BW, solids-corrected milk (SCM)/100 kg of BW, and unité fourragère lait (net energy requirements for lactation equivalent of 1 kg of standard air-dry barley; UFL) available for standard (4.0% fat and 3.1% protein content) milk production after accounting for maintenance. During the DMI measurement periods HF had a greater milk yield (23.2 kg/cow per d) compared with JEX and 3WAY (22.0 and 21.9 kg/cow per d, respectively) but there was no difference in MSo yield. Holstein-Friesian and JEX, and JEX and 3WAY had similar DMI, but HF had greater total DMI than 3WAY (DMI was 17.2, 17.0, and 16.7 kg/cow per d for HF, JEX, and 3WAY, respectively). Jersey × Holstein-Friesian cows were the most efficient for total DMI/100 kg of BW, SCM/100 kg of BW, and MSo/100 kg of BW (3.63, 4.96, and 0.39 kg/kg of BW) compared with HF (3.36, 4.51, and 0.35 kg/kg of BW) and 3WAY (3.45, 4.63, and 0.37 kg/kg of BW), respectively. Unité fourragère lait available for standard milk production after accounting for maintenance was not different among genotypes. As expected, DMI differed significantly among parities with greater parity cows having higher DMI and subsequently higher milk and MSo yield. Although all 3 genotypes achieved high levels of DMI and production efficiency, JEX achieved the highest production efficiency. Some of the efficiency gains (SCM/100 kg of BW, MSo/100 kg of BW, and total DMI/100 kg of BW) achieved with JEX decreased when the third breed (Norwegian Red) was introduced.

176 Evaluating Dual-purpose Wheat Varieties in the Southeastern U.S

Abstract Dual-purpose wheat (Triticum aestivum L.) systems increase farm sustainability by diversifying on-farm income. While these systems are common in the Southern Great Plains of the United States, they are not often utilized in the Southeast. This study aimed to evaluate pre- and post-grazing herbage mass (HM) of four winter wheat varieties managed under a dual-purpose grazing and grain production system. The winter wheat varieties evaluated were generic feed-type wheat (mixed variety, Feed), seed-type wheat (‘GA Gore’) and two forage-type varieties, ‘AGS 2024’ (AGS) and ‘Pioneer 26R41’ (Pioneer). The experiment was a completely randomized block design with n = 4. Each plot was randomly assigned either as no-grazing (CON) or grazing (GF2). Plots were grazed with cow-calf pairs that were fasted 24 h before each grazing event. Grazing was considered complete when the average stubble height was 10 cm. Herbage mass was determined using three 0.1m2-quadrats per plot and clipping to a 10 cm stubble height before (PreG) and after (PostG) each grazing event. Forage samples were then dried at 45°C for 72 h. Data were analyzed using PROC GLIMMIX of SAS (SAS Inst., Cary, NC). Differences were declared at P &amp;lt; 0.05. Initial HM was greater for PreG than PostG (883 and 615 kg/ha, respectively; P &amp;lt; 0.01). Prior to grazing, AGS (1204 kg/ha) was greater (P &amp;lt; 0.02) than all other varieties. Pre-grazing, there were no differences among the other varieties (776 kg/ha; P &amp;gt; 0.14). Post-grazing, AGS had a greater HM than Seed (788 and 391 ka/ha, respectively; P = 0.04), while all other varieties were intermediate (642 kg/ha). Herbage mass was affected by grazing frequency with CON being greater (P &amp;lt; 0.01) than GF2 (993 and 691 kg/ha, respectively). These results indicate that both wheat variety and grazing treatment had an effect on dual-purpose wheat herbage mass.

PSXI-16 Evaluation of supplementation strategies for beef cattle bale-grazing grass hay in Winter

Abstract Methods of supplementing beef cows while bale grazing grass hay were investigated in a study conducted for four winters, from 2016 to 2019, at the Central Grasslands Research Extension Center near Streeter, ND. Starting in the fall of each year, cows were assigned to eight groups of similar total body weight (BW) and allowed to bale graze one of four bale grazing treatments as follows: a) grass hay, b) grass hay supplemented with alfalfa hay, c) grass hay supplemented with corn DDGS, and d) grass hay treated with a liquid supplement. Two-day body weights and body condition scores (BCS) were taken at the start and end of the study. Final BW were greater (P ≤ 0.05) when cows were supplemented with DDGS and least when cows were not supplemented. Average daily gains were influenced by method of supplementation and year (P ≤ 0.025). When winters were cold, supplementation with alfalfa hay or a liquid supplement were not adequate to maintain cows resulting with weight loss. Final BCS were greatest (P ≤ 0.05) when cows were supplemented with DDGS and lowest on grass hay. Similarly, change in BCS was greatest in DDGS-supplemented cows and lowest on grass hay only. Calf birth weights, weaning weights and daily gains were not influenced (P &amp;gt; 0.05) by method of supplementation. Results suggest that method of supplementation during bale grazing should be based on prevailing environmental conditions during winter. In severely cold winters, good-quality alfalfa hay or a liquid supplement are not adequate to meet requirements of pregnant beef cows in mid-gestation. Under such conditions, supplements such as corn DDGS will be needed to meet animal requirements. Supplementation with good-quality alfalfa hay or grass hay treated with a liquid supplement may be an option during mild winters.

Grazing impacts on ground beetle (Coleoptera: Carabidae) abundance and diversity on semi‐natural grassland

Abstract Semi‐natural grasslands are commonly managed as a grazing resource for domestic livestock but, due to their unique biodiversity, they are also of conservation interest. Numerous drivers have impacted on the status of these grasslands in recent decades, most importantly changing grazing management strategies. These changes have the potential to affect the biodiversity associated with these habitats, including on some rich invertebrate assemblages. Responses, however, are often dissimilar between different invertebrate taxa. We investigated the responses of ground beetles to different grazing regimes within a replicated, controlled, long‐term grazing experiment on upland semi‐natural grassland in Scotland. Although there was substantial overlap of species composition of ground beetle assemblages in different grazing treatments, species richness, abundance and Shannon diversity of ground beetles were significantly lower in ungrazed plots than in plots subject to high‐ or low‐intensity sheep grazing. Ground beetle abundance (but not species richness or diversity) was lower in ungrazed plots compared to those with low‐intensity mixed grazing by sheep and cattle. However, no differences were identified in abundance, species richness or diversity between the three grazed treatments. Our results suggest that ground beetles may show different responses to grazing compared to responses of some other invertebrate groups and demonstrate the difficulty of attempting to manage grazing to optimise conditions for a wide range of invertebrates.

Effects of grazing corn plant residue on beef cattle performance, residue characteristics, and subsequent crop yield

Our objective was to evaluate the effects of grazing method on beef cattle performance, residue characteristics, and subsequent corn grain yields. This was a 3-yr study in which strip-grazing (SG), continuous grazing (CG), and ungrazed control (CT) treatments were arranged in a randomized complete block design with 3 replications per year on a continuous corn production system in central Illinois. Strip-grazed plots were divided into subplots (1, 2, 3) in which cattle back-grazed. Thirty-six spring-calving, multiparous, Angus cows were used in the first and second year of the study and 42 winter-calving Angus heifers were used in the third year. Cattle grazed for 42 d each year following corn harvest. Cattle in SG plots were 9.8 kg heavier ( P = 0.05) postgrazing compared with those on CG plots but did not differ ( P = 0.77) in final BCS, indicating adequate performance was maintained regardless of treatment. The SG and CG plots had increased ADF ( P = 0.03) and decreased CP ( P < 0.01) after grazing compared with CT. In year 2 postgrazing, SG and CG had decreased ( P < 0.01) total residue availability, leaves and husks, and cobs compared with CT, suggesting more digestible, nutrient-dense components were selected during grazing. No differences ( P = 0.16) were detected for corn yield among grazing treatments. However, yield was different ( P = 0.05) among strips. Strip 1 had lower yields than strip 2, which may have been due to increased cattle trafficking in this area. Both grazing methods resulted in acceptable performance. Grazing corn residue did not affect subsequent crop yields; however, strip differences in yield within strip-grazed paddocks warrant further investigation.

Grazing intensity changed the activities of nitrogen assimilation related enzymes in desert Steppe Plants

BackgroundNitrogen, as a limiting factor for net primary productivity in grassland ecosystems, is an important link in material cycles in grassland ecosystems. However, the nitrogen assimilation efficiency and mechanisms of grassland plants under grazing disturbance are still unclear. This study investigated Stipa breviflora desert steppe which had been grazed for 17 years and sampled the root system and leaf of the constructive species Stipa breviflora during the peak growing season under no grazing, light grazing, moderate grazing and heavy grazing treatments. The activities of enzymes related to nitrogen assimilation in roots and leaves were measured.ResultsCompared with no grazing, light grazing and moderate grazing significantly increased the activities of nitrate reductase (NR), glutamine synthetase (GS), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvate transaminase (GPT) in leaves, and GS, GOT and GPT in roots of Stipa breviflora, while heavy grazing significantly decreased the activities of GS in leaves and NR in roots of Stipa breviflora. NR, GOT and GPT activities in leaves and roots of Stipa breviflora were positively correlated with nitrogen content, soluble protein, free amino acid and nitrate content.ConclusionsGrazing disturbance changed the activities of nitrogen assimilation related enzymes of grassland plants, and emphasized that light grazing and moderate grazing were beneficial for nitrogen assimilation by grassland plants. Therefore, establishing appropriate stocking rates is of great significance for material flows in this grassland ecosystem and for the stability and sustainable utilization of grassland resources.