Short-duration Grazing System 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.

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>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<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>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.

Soil shear strength under non-irrigated and irrigated short duration grazing systems

Pasture productivity can drop due to soil compaction caused by animal trampling. Physical and mechanical alterations are therefore extremely important indicators for pasture management. The objective of this research was to: draw and evaluate the Mohr failure line of a Red Yellow Latossol under different pasture cycles and natural forest; calculate apparent cohesion; observe possible physical alterations in this soil; and propose a correction factor for stocking rates based on shear strength properties. This study was conducted between March/2006 and March/2007 on the Experimental Farm of Fundação de Ensino Superior de Passos, in Passos, state of Minas Gerais. The total study area covered 6 ha, of which 2 ha were irrigated pasture, 2 ha non-irrigated pasture and 2 ha natural forest. Brachiaria brizantha cv. MG-5 Vitória was used as forage plant. The pasture area was divided into paddocks. The Mohr failure line of samples of a Red Yellow Latossol under irrigated pasture equilibrated at a tension of water content of 6 kPa indicated higher shear strength than under non-irrigated pasture. The shear strength under irrigated pasture and natural forest was higher than under non-irrigated pasture. At a tension of water content of 33 kPa no difference was found in shear strength between management and use. Possible changes in soil structure were caused by apparent cohesion. The values of the correction factor were close to 1, which may indicate a possible soil compaction in prolonged periods of management.

Effects of grazing intensity and prescribed fire on soil physical and hydrological properties and pasture yield in the savanna woodlands of Burkina Faso

In West Africa policies for prescribed early fire and livestock grazing in the savanna woodlands are rarely based on long-term experimental studies. The inherently different management characteristics and their effects on the vegetation dynamics make landscape degradation a contentious issue. The effects of grazing intensity were investigated by a comparison of non-grazed areas, lightly grazed areas, moderately grazed areas, heavily grazed areas and very heavily grazed areas that received one of two fire treatments: early burning and fire protection in a long-term 12-year study. The parameters assessed reflected changes in herbaceous plant cover, biomass as well as soil physical and hydrological properties. The main findings were by and large specific for the grazing level. This supports the argument for devolution of management responsibility to the local level where there is indigenous site-specific knowledge but at the same time insufficient management capacity. A comparison of composite soil samples taken at a depth of 0–10 cm did not differentiate significantly between treatments. This is probably because the composite soil sampling procedure hid the properties of the top first few centimeters. Grazing pressure had a tendency to reduce total above ground biomass (p = 0.081). This was related to increased biomass removal and the trampling pressure (static load) exerted by the animals. The infiltration measurements indicated that the deleterious impact of cattle trampling increased as stocking rate increased. Livestock grazing significantly (p = 0.038) lowered the infiltrability. Prescribed early fire had a tendency (p = 0.073) to reduce the soil water infiltration rate. The subplots subjected to prescribed burning had a lower steady state infiltration rate compared to unburnt areas (means of 49.2 ± 27.5 mm h−1 versus 78 ± 70.5 mm h−1 for burnt and unburnt subplots, respectively). A partial least squares projection to latent structures showed that 34% of the steady state infiltrability was explained by the stocking rate and soil organic matter. Also all soil characteristics were significantly connected to steady state infiltrability suggesting that they are related to the soil hydrological response to trampling. From a management perspective, adoption of a short duration grazing system should avoid high stocking rates because they may adversely affect soil infiltrability, increase susceptibility to erosion in the savannas and decrease biomass productivity.

Least limiting water range: A potential indicator of changes in near-surface soil physical quality after the conversion of Brazilian Savanna into pasture

The Brazilian savanna, or “Cerrado”, is an ecosystem that originally covered more than 200 Mha in Brazil. It is estimated that about 49.5 Mha in the Cerrado are now covered with cultivated pastures, which are responsible for half of Brazilian beef production. However, soil and pasture degradation represent a threat to this productive system and to the Cerrado ecosystem itself. Thus, the objective of this research was to evaluate the least limiting water range (LLWR) as an index of near-surface soil physical quality after conversion of Brazilian savanna to continuous and short-duration grazing systems. Three sites were evaluated: native Cerrado (NC), continuous grazing (CG), and short-duration grazing (SG). Thirty soil cores (5 cm height, 5 cm diameter) were collected at each site, and used for soil bulk density, soil water retention curve, and soil penetration resistance curve determinations. The results were used for quantification of LLWR and critical bulk density ( D bc), in which LLWR equals zero. The near-surface soil physical quality, as evaluated by the LLWR, was most restrictive for potential root growth in SG. In CG, potential restriction was moderate; however, the entire soil bulk density range was below the D bc. In NC, potential restriction was minimum. The soil structural degradation process was primarily related to the increase in stocking rates in the grazing systems. The LLWR proved to be a useful indicator of Cerrado soil physical quality, being sensitive to alterations in near-surface physical properties.

Evaluation of soil compaction in an irrigated short-duration grazing system

Reduction in pasture productivity is generally attributed to alterations in soil quality. Soil compaction due to animal trampling is one of the factors responsible for the degradation of the physical quality of soils under pasture. The objective of the study was to evaluate penetrometer resistance (PR) in an irrigated short-duration grazing system at three post-graze residue levels. PR and moisture were simultaneously measured in plots containing three different post-graze residue levels (1000, 2500 and 4000 kg dry material ha −1). The influence of soil moisture on PR was taken into account using regression analysis techniques. PR was significantly higher for the treatments characterized by a small amount of post-graze residue, while similar values were obtained for the other two treatments. From a management perspective, adopting an irrigated short-duration grazing system with high stocking rate may adversely affect the soil physical quality.

Aplicações da curva de resistência no controle da qualidade física de um solo sob pastagem

A degradação da qualidade física do solo pode estar associada com a compactação causada pelo pisoteio dos animais. A resistência do solo à penetração (RP) é um parâmetro físico utilizado para estabelecer o grau de compactação do solo. Contudo, esta varia com a umidade (teta) e densidade do solo (Ds). O objetivo deste trabalho foi obter a curva de resistência do solo e utilizá-la na avaliação da qualidade física do solo num sistema de pastejo intensivo rotacionado de capim-elefante. A curva de resistência do solo foi determinada por meio de 48 amostras indeformadas, obtidas na profundidade de 0-10 cm numa Terra Roxa Estruturada utilizada com pastagem em sistema intensivo de exploração. Os resultados demonstraram correlação negativa entre a RP e teta, e correlação positiva entre RP e Ds. Estimativas indicaram que no potencial de -0,01 MPa a RP não atinge valores considerados restritivos ao crescimento radicular. Entretanto, no potencial de -0,3 MPa, a RP atinge níveis limitantes em toda a área. Quanto ao sistema de manejo e a espécie estudada, os resultados sugerem que a curva de resistência do solo pode ser utilizada para orientar as práticas de manejo visando à manutenção de uma qualidade física do solo adequada para o crescimento das plantas.

Spatial heterogeneity of soil properties in areas under elephant-grass short-duration grazing system

Soil properties can be changed by several factors, such as plant roots and animal trampling. The identification of spatial heterogeneity of these properties depends on the sampling scale. This study was developed to test the hypothesis that soil chemical and physical properties beneath elephant-grass plants are different from those between them. The research was carried out in a soil classified as Kandiudalfic Eutrudox. Forty-eight soil samples were collected from 0-10 cm depth (24 beneath plants and 24 between plants). The following properties were measured: pH, organic matter, S, available P, K, Ca and Mg exchangeable, sum of bases, cation exchange capacity, base saturation percentage, dry-aggregate distribution, bulk density and soil penetration resistance. Statistical analyses (t test) indicated that there were no significant differences in soil chemical properties in relation to spatial position. However, significant differences were observed in soil physical properties, with higher values of bulk density and soil resistance to penetration between the plants than beneath the plants.

Simulated Cattle Fever Tick Infestations in Rotational Grazing Systems

Prior simulation analysis of cattle fever tick population dynamics has indicated that fixed rotation, short duration grazing (SDG) systems could mediate the spread of ticks among pastures if rest periods were greater than 100 to 150 days. A question arose whether variable rotations with rest periods approaching 35-70 days could mediate the spread of ticks within these rapid, rotational grazing systems. An 8-pasture:1-herd extensive (26-34 days:l82-238 days graze:rest) and intensive (5-10 days: 35-70 days graze:rest) short duration grazing system was simulated over a 2-year period after a spring and fall introduction of infestated animals using a model depicting both temporal and spatial processes involved in host-parasite-landscape interactions. The extensive SDG system was infested for 639 and 424 days for spring and fall introductions, respectively. The intensive SDG system was continuously infested throughout the 24-month simulation. Although the intensive SDG system was continuously reinfested, there were more frequent tick-free periods in the fall introduction than the spring introduction. These simulations indicate that rest periods exceeding 150 days are necessary to minimize the rate and extent of spread of ticks in variable rotational grazing systems. These considerations are pertinent to the goals of both control and eradication strategies.

Effect of three grazing intensities on selected soil properties in semi‐arid west Texas

Soils in the study, carried out in the Texas Trans-Pecos region, were fine-loamy, mixed, thermic Aridic Calciustolls; fine-loamy, mixed, thermic Aridic Usthochrepts; and fine, mixed, thermic Typic Chromusterts. Our primary objective was to determine the effect of three grazing intensities within an intensive, short-duration grazing system on selected soil physical properties. Maximum compaction occurred in the A2/AB horizons, which has significantly higher (P Keywords: bulk density; conductivity; density; grazing intensity; infiltration; infiltration rates; organic carbon; porosity; properties; semi-arid; short duration grazing; soil compaction; soils; texas; treatments; u.s.a. African Journal of Range & Forage Science , 10(2): pp. 82-85

Influence of Spanish Goats on Vegetation and Soils in Arizona Chaparral

The key to managing Arizona chaparral depends on creating and maintaining brush-free or savanna-like habitats. Brush control using fire, chemicals, and mechanical methods has been tested previously; but limited information is available on goats. This study evaluated the effect of 4 goat-stocking levels in a short duration grazing system and mechanical brush crushing on chaparral shrubs, herbaceous vegetation, litter, and soils. After 4-1/2 years, percent total shrub cover was lower (P<0.05) on paddocks stocked at 1.4, 2.4, and 4.2 Spanish goats/ha (35, 39, and 38%, respectively) compared to unstocked controls (51%). Crushing brush increased the effectiveness of goats; mean total shrub cover was lower (P<0.05) on paddocks where brush was crushed vs not crushed (33 and 50%, respectively). Shrubs least preferred by goats were not affected, while preferred browse was impacted at all stocking levels. Goat stocking and brush treatments did not affect perennial herbs, while annuals were generally increased by soil disturbance. Less litter (P<0.05) accumulated under shrubs subjected to heavy stocking levels compared to unbrowsed paddocks. Concentrations of N and P in the soil were also affected (P<0.05) under desert ceanothus (Ceanothus greggii Gray) where the soil bulk density was also increased (P<0.05). While goats can reduce total shrub cover, problems may result. Perennial herbaceous vegetation did not respond. Shrubs preferred by goats were also preferred by native deer. Reduced forage diversity and nutritional stress could result if these species were eliminated from the stand. Also, trampling disturbance by goats affected nitrogen accumulation in the litter and soil, but more importantly heavy browsing may eliminate nitrogen-fixing shrubs.

Plant Community Responses to Short Duration Grazing in Tallgrass Prairie

A key to management of short duration grazing systems is maintaining proper rest periods for individual pastures, but information on the necessary length of rest periods for tallgrass prairie is limited. Research hypotheses for this study were that tallgrass prairie plant communities would respond differently to grazing schedules incorporating rest periods of varying lengths and that this response would be dependent on stocking rate. Treatments consisted of 3 grazing schedules (2, 3, or 4 rotation cycles per 152 day grazing season) and 2 stocking rates (1.6 and 2.2 times the moderate continuous rate). Plant frequency, standing crop, species composition, and forage utilization were sampled from 1985 to 1989. Precipitation was above average in 4 of the 5 study years. Grazing schedule did not affect any vegetation parameter over time. Stocking rate did not affect plant frequency or species composition. Standing crop was reduced and forage utilization increased at the higher stocking rate but these effects were consistent over time. Frequency of western ragweed [Ambrosia psilostachya DC.] and the relative species composition of the forb component increased in all grazed pastures compared to ungrazed pastures. The overall lack of major treatment effects was attributed to favorable precipitation, spring burning, and the initial high-seral successional stage of the experimental pastures.

Defoliation Frequency and Intensity Effects on Pasture Forage Quality

Both quantity and quality of pasture forage produced generally varies with frequency and intensity of plant defoliation. However, intensity and frequency of defoliation have rarely been evaluated simultaneously. The objective of this study was to quantify forage quality response to simultaneous changes in defoliation treatments over a range of values likely to occur in short-duration grazing systems. Effects of defoliation treatments on forage digestibility (DMD), crude protein content (CPC), crude protein yield, and digestible dry matter yield were evaluated on a perennial ryegrass (Lolium perenne, L.)-subclover (Trifolium subterraneum L.) hill land pasture growing on a Ultic Haploxeroll soil near Corvallis, Oregon. Treatments consisted of all possible combinations of 4 defoliation intervals (clipped every 7, 21, 35, or 49 days) and 3 stubble heights (High-70, Medium-55, or Low-40 mm of stubble remaining after defoliation) applied during the 1980, 1981, and 1982 growing seasons. Digestible dry matter yield increased with increasing defoliation interval. With the exception of DMD in 1980, both digestibility and CPC of the forage produced decreased linearly as the period between defoliation events increased. Crude protein content increased linearly as stubble height increased, while forage digestibility was comparatively insensitive to changes in stubble height. Forage quality was generally adequate on all treatments to meet the needs of most classes of livestock.

Diet Composition of Angora Goats in a Short-Duration Grazing System

Botanical and chemical compositions of Angora goat (Capra hircus) diets, determined with esophageally cannulated animals, were studied with and independent of a cattle-sheep-goat herd in a short-duration grazing (SDG) system. The study site consisted of 2 pastures in a 14-pasture, 1-herd SDG system. Each collection period in both pastures began when 44 animal units of livestock moved into either pasture 1 or 2. This methodology allowed a comparison of diet selection with and without grazing pressure. Goats selected more grass during the summer and fall than during the winter and spring. Browse was preferred over grass and forbs. Generally, higher crude protein values tended to be associated with large amounts of browse and forb selection. In vitro digestibility was highest in April and lowest in August. Crude protein was highest in April and lowest in November. Under this particular stocking rate (.19 animal unit years/ha) and weather conditions, we concluded that increased grazing pressure, caused by a 4-day graze period in a SDG system, had little effect on goat nutrition.

Tiller Defoliation Patterns under Short Duration Grazing in Tallgrass Prairie

Simulated 8-pasture short duration grazing systems were studied in 1985-86 to determine the effect of grazing schedule and stocking rate on defoliation patterns of individual grass tillers of big bluestem (Andropogon gerardii Vitman) and little bluestem (Schizachyrium scoparium (Michx.) Nash). Treatments consisted of 3 grazing schedules (2,3, or 4 rotation cycles per 152-day grazing season) and 2 stocking rates (1.3 and 1.8 times the recommended normal). Grazing schedule and stocking rate did not affect the percent tiller height reduction per grazing period except for the combination of 2-cycle grazing and heavy stocking which increased percent height reduction. Percent tiller height reduction per grazing period decreased over the grazing season for the 3 and 4-cycle grazing schedules. Grazing schedule and stocking rate had little effect on the height at which tillers were defoliated. Increasing the number of grazing periods reduced the percentage of tillers defoliated per grazing period but increased the cumulative defoliation frequency over the grazing season. Grazing schedule did not affect the percentage of tillers ungrazed over the entire grazing season. Big bluestem was consistently defoliated more intensely and frequently than little bluestem.

Vegetation Response to Increased Stocking Rates in Short-Duration Grazing

Short-duration grazing (SDG) has been purported to increase forage production and utilization compared to other grazing systems, and thus can sustain higher stocking rates. This study was designed to determine if standing crop could be maintained as stocking rates increased. Four stocking rate treatments ranging from the recommended rate for moderate continuous grazing to 2.5 times the recommended rate were applied in a simulated 8-pasture SDG system. There was little change in frequency and composition of short-grasses over the study, but mid-grass frequency and composition both declined. Standing crop of all major forage classes declined as stocking rates increased. However, the rate of decline was less than proportional to the increase in stocking rate during the growing season. By fall, standing crop was inversely proportional to stocking rate, leading us to conclude that standing crop could not be maintained at the higher stocking rates. Low standing crop in the fall indicated a potential shortage of forage at the high stocking rates during the winter.

Short-duration grazing on crested wheatgrass ( Agropyron desertorum): Effects of grazing system variables on cattle and herbage production

This exercise investigated the effects of short-duration grazing (SDG) variables on herbage production and cattle production on desert foothills. The hypothesis that stocking could be increased under SDG while maintaining grass stand integrity was also examined. Number of paddocks, length of stay per paddock and stocking rate were systematically varied under dry, average and wet years. Simulations of season-long grazing under various stocking rates and precipitation regimes provided a series of control runs. Factors controlling biological productivity of SDG systems were climate, stocking rate and number of grazing rotations per season. The latter two factors gave rise to two functional attributes, frequency and intensity of herbage defoliation, both of which decreased herbage production. Livestock production per area displayed a quadratic response to stocking rate and declined as the number of rotational cycles increased. In dry and average precipitation years, cattle production per area was higher under SDG than under season-long grazing; in wet years, production in season-long and SDG systems was similar. When seasonal herbage utilization was constrained to the maximum permissible for stand replacement (70%), SDG systems with one grazing rotation per season were able to carry 40% and 15% more animals than season-long grazing systems under dry and average herbage growth conditions, respectively. This exercise suggested that stocking rates can be increased slightly under SDG, but only under a limited range of conditions. Increased stocking rates under SDG were due to a predicted increase in efficiency of forage harvest by livestock.

Soil and Vegetation Responses to Simulated Trampling

An artificial hoof was used to simulate trampling effects on native shortgrass sods in a greenhouse experiment. Severe to moderate trampling was applied to sods maintained under 3 soil water regimes. Trampling was done either throughout a 32-day period to represent a continuous grazing system, or only during the last 4 of the 32 days to simulate a short-duration grazing system. Soil bulk density increased 3%, and infiltration rate declined 57% under severe trampling. Trampling throughout the 32-day period resulted in 4% higher bulk density than did a similar level of trampling that was applied only during the last 4 days of the trial. Dead vegetation was more easily removed by hoof action than was living vegetation, and severe water stress made plant material more brittle. Aboveground biomass production was 7% greater under trampling that simulated short-duration grazing, and 17% more forage remained in the standing crop under this treatment. About 38% more vegetation was detached by hoof action under simulated continuous grazing as compared with the short-duration grazing

Defoliation of Intermediate Wheatgrass under Seasonal and Short-Duration Grazing

Defoliation of intermediate wheatgrass (Agropyron intermedium by cattle was examined under seasonal and short-duration grazing. Tiller height, number of green leaves per tiller, phenological status, and defoliation frequency were measured on individually marked tillers during 2 grazing seasons. Defoliations at high and low stocking densities (5.2 and 2.6 animal-units/ha) were examined during the 1983 growing season. At equal stocking rates, standing crop decreased more rapidly under low stocking density. Mean tiller height and mean number of leaves per tiller decreased linearly over time in both treatments. In 1984, 14 heifers were moved through 3 rotations of an 8 subunit short-duration grazing system in 72 days. A larger fraction of tiller height and a higher number of green leaves per tiller were defoliated during rotation one than during rotation three. Animals grazed the greatest number of tillers during rotation one. Biting rate varied logarithmically with the mean number of green leaves per tiller. Time spent grazing was significantly and inversely related to the mean number of green leaves per tiller. This result suggests that animals were selectively grazing green leaves over coarse stem, and spent more time searching for them as their numbers decreased.