Short-duration Grazing Research Articles

PSIV-A-1 Comparing early and late spring grazing of cereal rye utilizing a high-density, short-duration grazing system

Abstract The objective of this study was to compare forage yield, nutritive value, grazing forage disappearance, in situ dry matter (DM) disappearance, and neutral detergent fiber (NDF) digestibility between late- and early-grazed cereal rye. Cover crop grazing time varies from year to year due to environmental and management conditions. Cereal rye is a high-yielding forage cover crop; however, rye matures quickly and subsequently declines in nutritive value. This experiment was conducted at Western Illinois University Kerr Farm, Macomb, IL. The late-grazed rye was planted October 9, 2020, while the early-grazed rye was planted November 8, 2022. Rye was planted at a rate of 90 kg/ha with a no-till drill following corn harvest. In yr 1, cereal rye was grazed and sampled during anthesis (mid to late May). In yr 2, cereal rye was grazed and sampled during the late boot stage (in mid to late April). A high-density, short-duration grazing system was used in both years. Cow-calf pairs (n = 58 pairs) grazed 0.40-ha plots for 24 h per plot. Plots were randomly sampled in four locations before and after grazing within a 0.40 m2 forage ring to determine forage nutritive value, height, and yield. All grass within the ring was clipped at approximately 12 cm to mimic grazing. Samples were analyzed at Rock River Laboratories (Watertown, WI) for crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and neutral detergent fiber digestibility (NDFD) at 12, 30, and 48 h. In situ DM disappearance was determined using ruminally cannulated beef heifers. Data were analyzed using the MIXED procedure of SAS 9.4. Early-grazed rye had a greater (P < 0.01) CP and less (P < 0.01) NDF and ADF than late-grazed rye. Accordingly, early-grazed rye had more than 50% greater (P < 0.01) DM disappearance at 24 and 48 h compared with late-grazed rye. Moreover, early-grazed rye had greater (P < 0.01) NDFD at 12, 30, and 48 h. However, late-grazed rye was 108 cm taller (P < 0.01) before grazing and remained 10 cm taller (P = 0.04) than early-grazed rye after grazing. Late-grazed rye yielded (P < 0.01) more DM than early-grazed rye, 3,873 vs. 1,079 kg/ha, respectively. After grazing, more DM (P < 0.01) remained on early-grazed rye plots than late-grazed rye plots, 496 vs. 2,445 kg/ha, respectively. Cows consumed 20% more DM (P = 0.04) of the early-grazed rye compared with late-grazed rye. Overall, an early-grazed rye cover crop was more digestible with a greater nutritive value and resulted in greater grazing consumption using a high-density, short-duration grazing system.

The Influence of Grazing Systems on Bird Species Richness and Density in the Nebraska Sandhills

Grazing is the de facto method of habitat management used in much of the Nebraska Sandhills. Ranchers use a variety of grazing systems, and our goal was to evaluate the effects of systems on grassland birds. We estimated the species richness and density of grassland birds for three grazing systems used on private ranches: long, medium, and short duration grazing systems. We observed sixty species, and the grazing system with pastures utilizing long duration grazing periods had the highest estimates of species richness as well as the most heterogeneous habitat structure. Differences in species richness among systems were most pronounced in years of limited precipitation. Together, grasshopper sparrows (Ammodramus savannarum), western meadowlarks (Sturnella neglecta), and brown-headed cowbirds (Molothrus ater) accounted for 72% of our observations. We used a model comparison approach to determine the effects of habitat on the densities of six species. Densities of grasshopper sparrows and mourning doves showed effects of the grazing system. More species had higher densities in short duration, rotational systems than other grazing systems. However, species of grassland birds showed responses to a variety of cover types and habitat structures depending on life history needs. Regardless of the grazing system used, managers can use grazing and other tools such as prescribed burning to maintain habitat heterogeneity to support diverse bird communities.

PSI-A-12 Evaluation of Novel and Traditional Cover Crops Utilizing Cattle in High-Density, Short-Duration Grazing

Abstract The objective was to evaluate yield, nutritive value, and neutral detergent fiber digestibility (NDFD) of traditional and non-traditional cover crops utilizing short-duration, high-density grazing. This experiment was conducted at Western Illinois University Kerr Farm, Macomb, Il. Cow-calf pairs (n = 58) grazed 0.4046 hectare plots in spring 2021. Dry cows (n = 58) grazed 0.4046 hectare plots in the fall 2021. Grazing duration was 24 hours per plot. In the spring, five plots of rye were grazed. In the fall, two plots of kernza, two plots of cover crop mix (CMIX), and one plot of red clover were grazed. The cover crop mix contained 12 varieties including brassicas, legumes, cereal grains, and grasses. Kernza is a novel perennial crop harvested for grain in the summer and used for grazing in the fall and winter. Plots were randomly sampled four times pre and post grazing using a 0.4047 square meter forage ring. All grass within the ring was clipped leaving 10.16-15.24 cm of material to mimic grazing. Forage height was recorded using a tape measure. Samples were collected and dried prior to combining and averaging data. Data pre- and post-grazing included DM, forage height, and DM yield. Cattle intake was calculated using pre- and post-grazing DM yields. Samples were analyzed at Rock River Laboratories (Watertown, WI) for CP, aNDF, ADF, and NDFD at 12, 30, and 48 hours. Data were analyzed using the Mixed procedure of SAS 9.4. Means were determined using LSMeans and separated using the p-diff function. Pre-grazing height of rye was 141 cm, CMIX was 87.6 cm, while kernza and red clover were both 26.7 cm (P < 0.01). Rye was most abundant in kg/ha of DM pre-graze and post-graze (P < 0.01). Cows consumed over 50% of kernza and CMIX, but only 29% of rye (P < 0.01). Forage dry matter percentages did not differ. Kernza had a lower CP (6.36%) than rye (8.91%; P = 0.02). Kernza CP did not differ from CMIX at 7.78% (P = 0.19). Kernza had a 7.18% greater aNDF than rye (P = 0.04). The aNDF of CMIX (55.56%) was greater compared with red clover at 44.75% (P = 0.04). Kernza ADF was 49.22% compared with rye at 43.8% (P = 0.02). The CMIX had the most desirable NDFD at 12, 24, and 48 hours (P < 0.01). Data indicated that rye, kernza, red clover, and cover crop mixtures offer value in high-intensity, short-duration cover crop grazing in terms of nutritive value and NDFD for cattle. Rye had the greatest DM yield values but less consumption by cattle due to forage maturity.

Changes in Forage Quality and Cattle Performance with Short-Duration Grazing of Mesic Meadows in the Intermountain West

Managers tasked with balancing livestock production and wildlife habitat in mesic meadows face a unique set of challenges. These challenges are compounded in the arid western United States because mesic areas comprise only a small portion of the landscape yet provide vital forage and water resources to livestock and wildlife and are essential to underlying ecosystem integrity and function. Our objectives were to compare the effects of short-duration grazing treatments that varied by season and intensity on the quantity and nutrient quality of pasture forage and average daily gains (ADG) of yearling cattle. We established pastures (n = 15 total pastures) in mesic meadows at the University of Idaho Rinker Rock Creek Ranch in south-central Idaho and stocked them with heifers during 2019 and 2020. Heifers grazed six pastures in June (early-season; 16 d) and six pastures in August (late-season; 16 d) at moderate (30−40%) and high (70-80%) relative utilization levels (n = 3 pastures per treatment). Three pastures were not grazed by cattle representing controls. Forage was collected and analyzed for nutrient quality at pregrazing, postgrazing, and after a period of regrowth in late September. Contrasted against all other treatments, early-season grazing at a high-intensity produced forages with the highest crude protein (P < 0.001) and lowest neutral-detergent fiber (P ≤ 0.04) after regrowth. ADGs of yearling heifers were greater (P ≤ 0.01) during the first year of the trial than the second year. Differences in ADG were not associated with grazing season (P = 0.08) or intensity (P = 0.12), despite numeric differences. Forage quantity and quality and heifer ADG responses varied between years, likely due to spring and annual precipitation differences. This study demonstrates the effectiveness of early-season grazing at a high intensity for improving forage quality and increasing ADG of livestock grazing mesic meadows.

Grazing of Reed Canarygrass (Phalaris arundinacea) in Restored Wet Meadows

Reed canarygrass (Phalaris arundinacea) is a grass species that can dominate wet meadow plant communities. This study investigated if grazing by cattle on restored wet meadows suppresses reed canarygrass, thereby promoting the restored plant community. This study was conducted at two locations in northwest Minnesota, one managed by The Nature Conservancy (TNC) and the other a Minnesota Board of Water and Soil Resources (BWSR) wetland bank site. Management practices used were a patch-burn grazing treatment on the TNC site and a high-density, short-duration grazing rotation system on the BWSR site. A pretreatment survey of total species canopy coverage was conducted before grazing followed by periodic surveys up to 7 y after grazing started. Both the patch-burn grazing and the grazing rotation system reduced reed canarygrass canopy cover by 49% compared to non-grazed control sites 5–7 y after grazing. With a reduction in reed canary grass canopy coverage due to grazing, the plant community moved toward a community with higher canopy coverage of Carex pellita that met restoration goals. Some of the species change was to grasses like Kentucky bluegrass (Poa pratensis), which is an exotic, invasive grass in prairies. The changed plant community held steady in native plant species richness or had an increase in native plant species richness. This study demonstrates grazing reduces the cover of reed canarygrass, while meeting restoration goals for wet meadows.

Managing Forbs Preferred by Greater Sage-Grouse and Soil Moisture in Mesic Meadows with Short-Duration Grazing

Mesic meadows provide valuable water and forage resources for wildlife and livestock in the arid western United States. Greater sage-grouse (Centrocercus urophasianus), a species of conservation concern, rely on these habitats because they support forb species of high importance to broods during late brood rearing. Because mesic meadows comprise a small fraction of the landscape, identifying grazing strategies compatible with maintenance and production of mesic resources is vital to balancing livestock production with suitable conditions for sage-grouse. We evaluated relationships between short-duration grazing treatments and habitat components important to sage-grouse in mesic meadows. In 2019 and 2020, we implemented short-duration (16 d) grazing treatments that varied by season (Early: early June; Late: early August) and intensity (control: 0%, moderate: 30−40%, high: 70−80% relative use). We evaluated cover and biomass percentages of high importance forbs (HIF), soil moisture, and noxious weed cover before and after grazing and again after pasture regrowth (Early: ≈13 wk, Late: ≈6 wk). Short-duration treatments did not reduce HIF cover or biomass. Early-season (P = 0.018) and high-intensity (P = 0.04) grazing increased HIF cover during the pregrazing sample period from 2019 to 2020, suggesting positive effects of these treatments on HIF cover during the pregrazing sample period. Postgrazing HIF cover and biomass percentages remained similar across treatments. Percentages of HIF biomass after regrowth were greater (P = 0.04) in early-season than late-season treatments in 2020. Seasonal declines in soil moisture from pregrazing to regrowth sample periods were greater (P < 0.001) in early-season treatments than late-season treatments but not associated with grazing intensity (P = 0.60). Cover of noxious weeds remained unchanged under short-duration treatments. Our study emphasizes the potential of early-season, high-intensity grazing to increase HIF cover and biomass for brood-rearing sage-grouse in mesic meadows over short time intervals.

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.

High-intensity short-duration grazing during spring is not an effective habitat management tool for Northern Bobwhites in Colorado

Abstract Many wildlife species, like Northern Bobwhite (Colinus virginianus), are reliant on periodic environmental disturbance to maintain heterogeneity in vegetation patterns. The Northern Bobwhite is a species of conservation concern requiring different vegetation types for nesting and brood-rearing stages, as well as for protection from predators and extreme weather. In northeastern Colorado, there are few management options to increase disturbance, other than domestic livestock grazing, to manage Northern Bobwhite habitat. As high-intensity short-duration grazing has shown promise as a mode of disturbance to manage Northern Bobwhite habitat in other regions, I used a randomized block design to test the effect of spring high-intensity short-duration grazing on Northern Bobwhites and their habitat in northeastern Colorado from 2016 to 2019. Specifically, I monitored Northern Bobwhite nest and brood survival and habitat selection in relation to grazing treatments over 3 years. I found that grazing had no effect on nest or brood survival or brood habitat selection, but Northern Bobwhites selected against grazed plots for nesting. Nest survival was negatively influenced by percent litter around the nest, and Northern Bobwhites selected nest sites with more grass cover and less bare ground. Broods selected habitat with less bare ground and more woody vegetation. Grazing affected vegetation immediately after grazing, but these effects weakened or disappeared by the end of the growing season. One exception to this overall pattern was forbs, which tended to be more abundant on grazed plots throughout the growing season. Overall, I found neutral effects of grazing on Northern Bobwhite nest and brood survival and habitat selection and neutral to positive benefits to the vegetation. Spring high-intensity short-duration grazing does not appear to be an effective tool to manage Northern Bobwhite nest or brood habitat in northeastern Colorado.

Wildlife-Friendly Livestock Management Promotes Mammalian Biodiversity Recovery on a Semi-Arid Karoo Farm in South Africa

Agriculture is an essential production system used to feed the growing human population, but at the same time has become a major driver of biodiversity loss and environmental degradation. Employing production methods that restore degraded landscapes can have a positive impact on biodiversity, whilst improving food production. We assessed how mammalian biodiversity, specifically richness and their relative abundances varied on five Karoo farms in South Africa that had been amalgamated and subjected to a transition from traditional livestock grazing techniques (sporadic rotational grazing and lethal predator control) to wildlife-friendly non-lethal predator management, using human shepherding of livestock under a high-density short-duration grazing regime. We used camera trap data collected over a 4-year period, to measure mammalian species richness, distribution and relative abundance on the wildlife-friendly farm to investigate temporal changes throughout the conversion from traditional farming practices. In the last year of the study (2019) additional cameras were used to provide a spatial comparison of mammalian species on the wildlife-friendly farm to two neighboring farms, a traditional livestock farm using lethal predator controls, and a game farm. We found that mammalian species richness increased year on year resulting in a significant increase of 24% over the duration of the study. Herbivores showed an increase of 33% in the number of species detected over the years, while predator species increased by 8%. The relative abundance and distribution of most species also showed increases as the conversion process took place. For example, 73% of the herbivore species detected throughout the study increased in their relative abundance. Similarly, 67% of all species showed an increase in the number of sites occupied over the years. In the final year of the study the wildlife-friendly farm had more mammalian species compared to the game farm and traditional livestock farm, with the latter two sites having a similar number of species when compared to the commencement of the conversion of the wildlife-friendly site. These broad improvements in mammalian biodiversity demonstrate that livestock production can benefit local mammalian biodiversity through a combination of herder grazing management and wildlife-friendly farming.

INFLUÊNCIA DO SISTEMA DE PRODUÇÃO NA PRODUTIVIDADE DE LEITE NO INTERIOR DO ESTADO DE SÃO PAULO, BRASIL

Esta pesquisa teve como objetivo avaliar a influência do sistema de produção sobre a produtividade de leite em propriedades rurais da microrregião de Birigui, São Paulo, Brasil. O estudo se baseou em coleta de dados dos sistemas de produção de leite da região citada, por meio de entrevista estruturada. Realizou-se amostragem por conveniência, sendo escolhidos 15 produtores de cada estrato produtivo (de acordo com a produção diária de leite: pequeno - até 100 L; médio - 101 a 300 L; grande - mais de 300 L), totalizando uma amostra com 45 produtores de leite. Apenas propriedades com base da alimentação volumosa em sistema de pastejo ou, no máximo, em semicofinamento participaram da pesquisa. Para avaliação da influência de diferentes fatores sobre a produtividade de leite, realizou-se regressão multivariada e análise de variância multivariada com pós-teste de Tukey. A produtividade verificada (média ± desvio padrão), que representa a variável resposta do estudo, foi de 6.274,9 ± 4.981,4 L/ha/ano. Com a análise estatística, pôde-se identificar a base da alimentação volumosa e a produção de leite por dia de intervalo entre partos como variáveis preditoras que influenciam a produtividade, sendo que a primeira foi a que exerceu maior influência sobre a variável resposta. Foi observado que não houve diferença (p&gt;0,05) entre a produtividade média das propriedades que utilizavam pastejo rotativo e das que forneciam volumoso no cocho, porém, em ambas, a produtividade foi superior (p&lt;0,05) às médias de produtividade das propriedades que usavam pastejo contínuo e das que usavam pastejo alternado, sendo que estas não diferiram entre si (p&gt;0,05). Em relação à base da alimentação volumosa, os resultados indicam a importância do manejo adequado de pastagens e demonstram a viabilidade da utilização, para produção de leite, de pastejo rotativo em vez de semiconfinamento. Quanto à produção de leite por dia de intervalo entre partos, os resultados denotam a importância da atenção à produção e à reprodução de forma conjunta, e não de forma isolada, para que haja eficiência produtiva no sistema. O foco do trabalho de produtores, técnicos, pesquisadores e outros participantes da cadeia produtiva do leite deve ser a sustentabilidade e o bem-estar animal.

Managing Grazing to Restore Soil Health, Ecosystem Function, and Ecosystem Services

Ruminants including domestic livestock, have been accused of causing damaging impacts on the global environment and human well-being. However, with appropriate management, ruminant livestock can play a significant role in efforts to reverse environmental damages caused by human mismanagement and neglect. Worldwide, at least one billion people living in grazing ecosystems depend on them for their livelihoods, usually through livestock production, and for other ecosystem services that affect human well-being. For long-term rangeland sustainability and ecological resilience, agricultural production policies are urgently needed globally to transform current damaging industrial inorganic input agricultural practices to resource conservation practices that enhance ecosystem function. This is supported by evidence that farmers and ranchers who apply regenerative management practices to restore ecosystem functionality create sustainable, resilient agroecosystems cost-effectively. With enhanced management of grazing resources, domesticated ruminants can be used to produce higher permanent soil cover of litter and plants, which are effective in reducing soil erosion and increasing net biophysical carbon accumulation. Incorporating forages and ruminants into regeneratively managed cropping systems can also elevate soil organic carbon and improve soil ecological function and reduce production costs by eliminating the use of annual tillage, inorganic fertilizers and biocides. Ecosystem services that are enhanced using regenerative land management include soil stabilization and formation, water infiltration, carbon sequestration, nutrient cycling and availability, biodiversity, and wildlife habitat, which cumulatively result in increased ecosystem and economic stability and resilience. Scientists partnering with farmers and ranchers around the world who have improved their land resource base and excel financially have documented how such land managers produce sound environmental, social, and economic outcomes. Many of these producers have used Adaptive Multi-Paddock (AMP) grazing management as a highly effective approach for managing their grazing lands sustainably. This approach uses short-duration grazing periods, long adaptively varied post-grazing plant recovery periods requiring multiple paddocks per herd to ensure adequate residual biomass, and adjustment of animal numbers as environmental and economic conditions change. Using this approach, farmers and ranchers have achieved superior ecosystem and profitability outcomes. This manuscript summarizes the use of AMP grazing as regenerative tool for grazed and rotationally cropped lands.

Adaptive rangeland management benefits grassland birds utilizing opposing vegetation structure in the shortgrass steppe.

Rangelands are temporally and spatially complex socioecological systems on which the predominant land use is livestock production. In North America, rangelands also contain approximately 80% of remaining habitat for grassland birds, a guild of species that has experienced precipitous declines since the 1970s. While livestock grazing management may benefit certain grassland bird species by generating the vegetation structure and density they prefer, these outcomes are poorly understood for avian species breeding in the shortgrass steppe. We evaluated how two grazing management systems, continuous, season-long grazing and adaptive, rest-rotational grazing, affected grassland bird abundance from 2013 to 2017 in Colorado's shortgrass steppe. We examined grazing impacts in conjunction with ecological sites, which constitute unique soil and plant communities. When grazing management was evaluated in conjunction with spatial variation in ecological sites, we found three of our five focal bird species responded to grazing management. McCown's Longspur abundance decreased in pastures rested from grazing the previous year. The effect of grazing on Horned Lark and Grasshopper Sparrow depended on ecological site: Horned Lark density was highest in pastures that were intensively grazed and Grasshopper Sparrow density was highest in pastures that were rested the previous year in the least productive ecological site. In addition, densities of all species varied across ecological sites. Our results suggest consideration of soil and vegetation characteristics can inform how adaptive management is applied on a landscape to benefit the full suite of breeding grassland birds, including species that have seemingly contrasting habitat needs. For example, a manager could target adaptive drought mitigation practices, such as resting pastures for 1 yr to generate grassbanks, in less productive soils to benefit grassland birds that prefer taller/denser vegetation structure, or could apply intensive, short-duration grazing on less productive soils to benefit species preferring shorter/sparser vegetation. A single year of intensive, short-duration grazing (i.e., one component of our rotational treatment) across the landscape, however, might not create sufficient habitat for species that prefer short/sparse vegetation in our system (e.g.,McCown's Longspur). Ultimately, our study indicates how cattle production on rangelands can congruently support grassland bird populations in the shortgrass steppe.

Short-duration rotational grazing leads to improvements in landscape functionality and increased perennial herbaceous plant cover

Livestock grazing can lead to reduced ground cover and altered composition of pastures through the loss of palatable forage species and reduced litter cover. This negatively impacts landscape function and ultimately livestock production. Grazing livestock for short periods with high animal density, followed by long rests to allow pasture recovery (short-duration grazing), could be a way to address these issues. In naturalised pastures, we assessed landscape functioning and compared the abundance of six major plant functional groups at 36 sites on 12 commercial grazing properties. Six of the properties had been managed with short-duration grazing for more than 7 years (in most cases over 10 years), while the six control properties were managed with grazing that was more typical of the region (relatively continuous throughout the year with unplanned rests). Under short-duration grazing, there was approximately 19% greater foliar cover of perennial herbaceous species with a corresponding 14% reduction in foliar cover of introduced annual plants. Attributes relating to biophysical functioning of the landscape were enhanced by short-duration grazing, with environmental factors less important in influencing these landscape function attributes. Higher-value forage species were also more abundant on short-duration grazing properties, especially at higher rainfall sites. Conversely, species that tend to increase under heavy grazing pressures, and are of lower forage value, were less abundant under short-duration grazing. Despite the changes in pasture composition in response to grazing management there was a large amount of unexplained variation in herbaceous community composition. This study demonstrates benefits for landscape function and naturalised pasture composition under short-duration grazing that has been in place for several years compared with more usual grazing practices.

Short Communication: Evaluation of 2 implants for growing steers grazing tall-grass prairie when using intensive early stocking

ABSTRACT Commercial implants can have different coating technologies, carriers, and hormone amounts that result in different payout characteristics and effects on cattle growth. Therefore, the objective of this study was to evaluate 2 implants in stocker steers on a 90-d grazing season. Implants were Revalor-G (REV), which contains 40 mg of trenbolone acetate and 8 mg of estradiol, is uncoated, and has a cholesterol carrier, or Synovex One Grass (SYN), which contains 150 mg of trenbolone acetate and 21 mg of estradiol benzoate and has a porous polymer coating. Steers (n = 242) were weighed with an overnight shrink on d 0, 44, and 91. Steers were implanted on d 0 and assigned to 1 of 7 pastures in a completely randomized complete block design with pasture as block. Total gains and gains in each half of the grazing season were evaluated. Average daily gain was not different based on implant type (P = 0.35; 1.16 kg/d for REV and 1.13 kg/d for SYN; SEM = 0.02) nor was total BW gain (P = 0.65; 101 kg for REV vs. 100 kg for SYN; SEM = 2.3). Additionally, BW gain and ADG were not different between implants in both sections of the grazing period (P ≥ 0.45). Overall, cattle performance was not different regardless of hormone amount and coating technology in implants in a short-duration grazing period with stocker steers, and these data do not support a price premium for SYN over REV in this grazing system.

Effect of the Silica Content of Diatoms on Protozoan Grazing

This study examined the effect that silica content in diatom cells has on the behavior of protists. The diatoms Thalassiosira weissflogii and T. pseudonana were cultured in high or low light conditions to achieve low and high silica contents, respectively. These cells were then fed to a heterotrophic dinoflagellate Noctiluca scintillans and a ciliate Euplotes sp. in single and mixed diet experiments. Our results showed that in general, N. scintillans and Euplotes sp. both preferentially ingested the diatoms with a low silica content rather than those with a high silica content. However, Euplotes sp. seemed to be less influenced by the silica content than was N. scintillans. In the latter case, the clearance and ingestion rate of the low silica diatoms were significantly higher, both in the short (6-h) and long (1-d) duration grazing experiments. Our results also showed that N. scintillans required more time to digest the high silica-containing cells. As the high silica diatoms are harder to digest, this might explain why N. scintillans exhibits a strong preference for the low silica prey. Thus, the presence of high silica diatoms might limit the ability of the dinoflagellate to feed. Our findings suggest that the silica content of diatoms affects their palatability and digestibility and, consequently, the grazing activity and selectivity of protozoan grazers.

Activity Patterns and Habitat Use of Northern Bobwhite Females in 2 Grazing Systems

During spring and summer of 1985 and 1986, we investigated activity patterns and habitat use of female northern bobwhite (Colinus virginianus) on 2 sites in south Texas. One site had been subjected to a short duration grazing (SDG) system and the other to a continuous grazing (CG) system. Nineteen females were radio-tagged in 1985 and 28 in 1986. Rainfall was above average in 1985 and below average in 1986; as a result, herbaceous ground cover was more dense in 1985 than in 1986. Due to extensive fencing, 58% of the SDG cell was within 25 m of a mowed roadside, fencerow, or pipeline right-of-way; the same was true for 30% of the CG pasture. There were no differences (P > 0.05) in distances moved between successive locations or in the breeding season home range sizes of females in the 2 systems. In 1985, females preferred zones within 25 m of mowed areas and avoided those ~50 m from such areas. In the SDG cell during 1986 only, females preferred recently grazed paddocks. The results suggest that the most important difference between the 2 grazing systems was the increased proportion of mowed areas in the SDG cell during the abnormally wet year. In the Texas Coastal Bend, landowners unable to adjust stocking rates during wet years should consider mowing to improve bobwhite habitat.

Potential of grassland rehabilitation through high density-short duration grazing to sequester atmospheric carbon

According to the World Resources Institute (2000), a relative increase of carbon (C) stocks in world soils by 0.4% per year would be sufficient to compensate all anthropogenic greenhouse gas emissions. Several land management practices such as the suppression of tillage in agroecosystems and livestock exclusion in grasslands had initially been thought to store more carbon into the soil, but recent research puts this into question. In a context where finding effective C sequestration methods is urgent, the main objective of this study was to assess the ability of an innovative grassland management practice based on high density and short duration (HDSD) grazing to sequester atmospheric C into soils. The study was performed in a degraded communal rangeland in South Africa where soil organic C (SOC) depletion ranged from 5 to 95% depending on the degradation level, which varied from non-degraded (ND; with grass above ground coverage, Cov of 100%), degraded (D1; 50<Cov<75%), D2 (25<Cov<50%) and HD (highly degraded: Cov<5%). The ability of HDSD (1200cows ha−1 for 3days a year) to replenish SOC stocks was compared to four commonly used strategies: (1) livestock exclosure (E); (2) livestock exclosure with topsoil tillage (ET); (3) livestock exclosure with NPK fertilization (2:3:3, 22 at 0.2tha−1) (EF); (4) annual burning (AB); all treatments being compared to traditional free grazing control. A total of 540 soil samples were collected in the 0–0.05m soil layer for all treatments and degradation intensities. After two years, topsoil SOC stocks were significantly increased under EF and HDSD, by an average of 33.4±0.5 and 12.4±2.1g C m2 y−1, respectively. In contrast, AB reduced SOC stocks by 3.6±3.0gCm2y−1, while the impact of E and ET was not significant at P<0.05. HDSD replenished SOC stocks the most at D1 and D2 (6.7 and 7.4%y−1) and this was explained by grass recovery, i.e. a significant increase in soil surface coverage by grass and grass production. HDSD is cost-effective, and thus has great potential to be widely adopted by smallholder farmers.

Long-term lesser prairie-chicken nest ecology in response to grassland management

Long-term population and range declines from habitat loss and fragmentation caused the lesser prairie-chicken (Tympanuchus pallidicinctus) to be a species of concern throughout its range. Current lesser prairie-chicken range in New Mexico and Texas is partially restricted to sand shinnery oak (Quercus havardii; hereafter shinnery oak) prairies, on which cattle grazing is the main socioeconomic driver for private landowners. Cattle producers within shinnery oak prairies often focus land management on shrub eradication using the herbicide tebuthiuron to promote grass production for forage; however, herbicide application alone, and in combination with grazing, may affect nest site selection and nest survival of lesser prairie-chickens through the reduction of shinnery oak and native grasses. We used a controlled, paired, completely randomized design study to assess the influence of grazing and tebuthiuron application and their combined use on nest site selection and nest survival from 2001 to 2010 in Roosevelt County, New Mexico, USA at 2 spatial scales (i.e., treatment and microhabitat) in 4 treatments: tebuthiuron with grazing, tebuthiuron without grazing, no tebuthiuron with grazing, and a control of no tebuthiuron and no grazing. Grazing treatment was a short-duration system in which plots were grazed once during the dormant season and once during the growing season. Stocking rate was calculated each season based on measured forage production and applied to remove ≤25% of available herbaceous material per season. At the treatment scale, we compared nest site selection among treatments using 1-way χ2 tests and nest survival among treatments using a priori candidate nest survival models in Program MARK. At the microhabitat scale, we identified important habitat predictors of nest site selection and nest survival using logistic regression and a priori candidate nest survival models in Program MARK, respectively. Females typically used treatments as expected and we did not detect trends in selection. Nest survival did not differ among treatments. At the microhabitat scale, nest sites had less bare ground (P = 0.001) and greater angles of obstruction (P ≤ 0.001) compared to random sites. There was a high degree of model selection uncertainty among our candidate models at the microhabitat scale and survival estimates were similar among habitat covariates. Results suggest a tebuthiuron application rate of 0.60 kg/ha, short-duration grazing, and a combination of these management techniques were not detrimental to lesser prairie-chicken nest site selection or nest survival. However, intensified management that increases bare ground or reduces overhead cover may negatively affect lesser prairie-chicken nesting habitat and nest survival. © 2016 The Wildlife Society.

Comparison of Beef Cattle Grazing Management Practices and their Effects on Runoff Water Quality in Louisiana

Management-intensive grazing (MIG) allows better use of grazed forage crops with short-duration grazing in small paddocks and with this study; the water quality was compared for two grazing management methods. Year-round grazing with MIG and continuous stocking (CS) were compared. Four 0.81-ha plots for two replications of the grazing systems were established. Twenty 0.04 ha (0.1 ac) paddocks, established with power fencing, allowed daily cattle rotation in MIG system. Continuous grazing and MIG used the same stocking rate on each experimental plot (0.81 ha). Each year, two crossbredbeef (Bos taurus) heifers (390 kg ± 12 kg; 12-14 mo at start) were maintained on each plot year-around for 3 yr, with additional yearling heifers added to maintain similarforage availability between stocking methods. Common bermudagrass (Cynodon dactylon [L] Pers.) was grazed in summer and annual ryegrass (Lolium multiflorum Lam.) was over-seeded into the sod during October for winter and spring grazing. Forage mass was determined monthly and available forage dry matter (DM) was maintained at approximately 1120 kg DM ha-1 Runoff water samples were collected during 42 rainfall events from May 2001 through March 2004. No significant treatment differences (P &gt; 0.10) were found in most of the water quality parameters. Runoff as a percentage of the 3-yr average annual rainfall of 1869 mm was 34% for MIG and 42% CS. The average flow-weightedconcentrations of soluble reactive phosphorus (SRP) varied from 5.08 mg P L–1 (ppm) to 8.22 mg P L–1 (ppm) while the NH+4–N ranged from 1.07 mg N L–1 (ppm) in year one to 10.11 mg N L–1 (ppm) for the second year (P &lt; 0.05) for year effect. Total annual average forage production was greater (P &lt; 0.05) in the MIG compared to CS with19,796 kg ha-1 for MIG vs. 16,964 kg ha-1 for CS. Beef production also increased with the MIG system with an annual total beef gain from MIG at 422 kg ha-1 y-1 vs. CS at 330 kg ha-1 yr-1.

Short-Duration Grazing in Retrospect—A Practitioner’s Experience

“Short-duration grazing” (SDG) is a common- sense approach to rangeland management that has been implemented, criticized, lauded, altered, and renamed since it was exposed to world scrutiny over 40 years ago. We now call this South Af- rican/Rhodesian–originated method of matching herbivores to plants “holistic planned grazing” (HPG). It has become an economic, environmental, and social improvement to the way land owners and managers approach animal use of grazing lands. Here I offer my own account of its history and my per- sonal viewpoint as to its current and future utility for range managers faced with the task of contributing to world food production in the face of climate uncertainties. DOI: 10.2458/azu_rangelands_v35i5_goodloe