Continuous Grazing Systems Research Articles

Predicted methane emissions and metabolizable energy intakes of steers grazing a grass/alfalfa pasture and finished in a feedlot or at pasture using the GrassGro decision support tool

Dry matter intakes (DMI) and methane (CH4) emissions from steers grazing alfalfa/(Medicago sativa L)/meadow bromegrass (Bromus biebersteinii Roem & Schult.)/Russian wild ryegrass [Psathyrostachys juncea (Fisch.) Nevski] at 1.1 and 2.2 steers ha-1 in continuous and rotational grazing systems at Brandon, Manitoba, during the 1994 grazing season were predicted using the GrassGro decision support tool and compared with those reported from a field experiment. Observed DMI (13.82 ± 0.39 kg d-1) did not differ significantly (P = 0.052) from predicted DMI (12.10 ± 0.19 kg d-1). Mean predicted CH4 (278.5 ± 2.2 g d-1) was greater (P < 0.002) than field observations (195.8 ± 9.7 g d-1). This difference may reflect the difficulty of ensuring total collection of all CH4 emitted in a field experiment. GrassGro predicted that feeding a barley supplement to the steers while at pasture would cause a small though significant increase (P < 0.001) in mean daily emissions of CH4 (287.8 ± 1.9 g d-1) compared with unsupplemented steers (274.1 ± 2.9 g d-1). However, when CH4 emissions were compared as g kg-1 liveweight gain (LWG), they were less (P < 0.0001) for supplemented (133.2 ± 6.4 g kg-1 LWG) than unsupplemented steers (199.1 ± 5.9 g kg-1 LWG). In addition, supplementing barley at pasture would reduce (P < 0.0001) the total emissions of CH4 (38.7 ± 2.1 kg) compared with backgrounding at pasture and finishing in a feedlot (54.4 ± 1.1 kg). This would also reduce (P < 0.001) the metabolizable energy intake (MEI) required for liveweight gain (68.3 ± 1.94 vs. 87.2 ± 1.20 MJ MEI kg-1 liveweight gain). We conclude that finishing cattle at pasture will reduce the total emissions of CH4 and increase the efficiency of conversion of feed energy to liveweight gain when compared with backgrounding at pasture and finishing in a feedlot. Key words: Methane, steers, grass, alfalfa, pasture, barley, feedlot, metabolizable energy intake

Continuous and rotational grazing of dairy cows – the interactions of grazing system with level of milk yield, sward height and concentrate level

AbstractAn experiment was conducted to test the hypothesis that for cows with high levels of milk yield, rotational grazing produces higher milk yields than continuous grazing. The comparison of grazing systems was made at two levels of milk yield (initially 20·3 and 32·5 kg d−1), and interactions with sward height and concentrate level were also examined. The study used 48 multiparous Holstein Friesian cows over a period of 62 d. Mean milk yield, its persistency and composition, live weight, body condition score and liveweight gain were not significantly affected by grazing system at either level of milk yield. There were no significant interactions between grazing system and sward height or concentrate level for any milk production measurement. Mean estimated herbage and total dry matter (DM) intake (P < 0·01), grazing time (P < 0·05) and ruminating time (P < 0·01) were significantly greater on the continuous grazing system. The cows in the higher milk yield group and those grazed at the higher sward height had a significantly (P < 0·05) higher estimated daily herbage DM intake and rate of herbage intake on the continuous grazing system than those on the rotational grazing system. There was no evidence to support the hypothesis that rotational grazing systems support higher levels of milk production than continuous grazing for cows of high milk yield. The shorter grazing time on the rotational grazing system indicated that cows may anticipate the timing of the daily movement of the electric fence, and this reduces their time spent grazing residual herbage.

Validating and using the GrassGro decision support tool for a mixed grass/alfalfa pasture in western Canada

This paper presents predictions of pasture composition and liveweight gain of steers using the GrassGro simulation model. Predictions are compared with field data measured during a 4-yr experiment at Brandon, Manitoba, in which steers grazed alfalfa (Medicago sativa)/grass (Bromus biebersteinii and Psathyrostachys juncea) pastures at 1.1 and 2.2 steers ha-1 in continuous or rotational grazing systems. The predictions of average daily gain, mean forage mass and botanical composition were found to accurately reflect the field data. Predictions of digestibility and protein were less accurate and reasons for this are discussed. Steers from the field trial were not considered finished for slaughter directly off pasture. GrassGro was used to examine the effects of feeding a barley supplement to the steers while at pasture. The results indicated that all steers could have been finished at pasture. Simulation indicated that supplementation at pasture makes the stocking rate of 2.2 steers ha-1 more attractive because twice the number of steers could be finished with little additional requirement for barley supplement. Further simulations provided information on the effects of climate variations during a 30-yr period (1967–1996) on steer production in both continuous and rotational grazing systems using a range of stocking rates from 1.1 to 5.5 steers ha-1. Key words: GrassGro, decision support, steers, grass, alfalfa, pasture

Suplementação energética na recria de bezerras de corte mantidas em pastagem de inverno

Este trabalho foi conduzido para se avaliar o efeito de níveis de suplementação energética no desempenho produtivo e reprodutivo de 64 bezerras de corte Charolês e suas cruzas com Nelore, mantidas em pastagem cultivada de aveia preta (Avena strigosa Schreb) mais azevém (Lolium multiflorum Lam.). Os tratamentos consistiram em suplementação equivalente a 0; 0,7 e 1,4 % do peso vivo (PV)/dia de farelo de arroz integral associado à polpa cítrica na proporção de 1:1. O método de pastejo foi contínuo, com lotação variável, visando manter massa de forragem de 1500 kg/ha de matéria seca (MS). Foram avaliados o ganho médio diário, carga animal, ganho de peso por área, condição corporal, área pélvica, peso à puberdade, idade à puberdade, altura da garupa e consumo estimado de MS. A suplementação proporcionou maior ganho médio diário, carga animal e ganho de peso vivo/ha. Bezerras alimentadas exclusivamente em pastagens tiveram menor condição corporal e apresentaram menor porcentagem de cio do que bezerras suplementadas. A percentagem de fêmeas que mostraram cio até os 16 meses de idade foi de 9,1; 68,7 e 70,6%, respectivamente. Os níveis de suplementação não interferiram em área pélvica, peso à puberdade, idade à puberdade e altura de garupa. O consumo estimado de MS foi menor no nível 1,4% do PV/dia.

Produção animal e retorno econômico da suplementação em pastagem de aveia e azevém

O experimento avaliou a resposta animal e o retorno econômico do uso da suplementação energética em pastagem de aveia preta (Avena strigosa Schreb) + azevém anual (Lolium multiflorum Lam). Os tratamentos foram: STP - Suplementação, durante todo o período de utilização da pastagem; SAS- Suplementação até final de setembro; SS- Sem suplementação. O sistema de pastejo foi o contínuo com lotação variável. O suplemento utilizado foi o grão de sorgo em quantidade variável para manter a mesma quantidade de massa de forragem em todos os tratamentos. O ganhos de peso médios diários por animal (GMD) foram superiores nos tratamentos STP e SAS, 0,716 e 0,710 kg, respectivamente, em relação ao obtido no tratamento SS (0,580 kg). A suplementação possibilitou maior carga animal. A produção animal por hectare foi maior em STP, 627 kg ha-1 de PV, sendo 75% superior aos 359 kg ha-1 de PV do SS. A suplementação não afetou a condição corporal dos animais. O custo total e a receita líquida foram de 775,42/165,08, 605,75/204,25 e 367,35/204,92 R$ ha-1 para STP, SAS e SS, respectivamente. O uso exclusivo da pastagem e a suplementação, até o final de setembro, resultaram em maior retorno financeiro direto.

Lessons from the Past: Have We Learned from Our Mistakes?

While the past is the necessary background for our future, mistakes from the past may now be hindering progress toward improved range management. We still cling to outdated range condition concepts and models, reporting of range condition has never been standardized, we lack consistent monitoring methodology, we often do not set monitoring objectives prior to monitoring, and we continue to use outdated "Rule-of-Thumb" concepts to manage. One such concept is that of range readiness, which delays start of grazing until a certain plant growth target has been met. While useful for continuous grazing systems, this concept may actually be detrimental when applied to a rotation system. Other rule-of-thumb concepts include using utilization as an objective when it properly is a tool, inappropriate use of rest, and continued efforts to attempt to determine apparent trend instead of measuring trend over time. We continue to perpetuate myths that have no basis in fact including: the Intermountain region evolved without heavy grazing pressure, the Western U.S. was "pristine" prior to arrival by European man, and bison were migratory animals which minimized their impact on the rangeland. Until we overcome these and other erroneous or outdated ideas from our past, we will continue to have problems making progress toward better management of our rangelands.

Produção Animal em Pastagem com Gramíneas de Estação Quente

Foi avaliado o desempenho de novilhos de corte, durante a fase de recria, em capim-elefante (Pennisetum purpureum Schum.) cv. Taiwan A-146, papuã (Brachiaria plantaginea (Link) Hitchc), sorgo forrageiro (Sorghum bicolor (L.) Moench) cv. AG 2501C e milheto (Pennisetum americanum (L.) Leeke) cv. comum. O período total de pastejo foi de 143 dias para a pastagem de capim-elefante e 98 dias para as demais pastagens. O sistema de pastejo foi o contínuo com lotação variável. O teor de proteína bruta na massa de forragem foi de 5,43; 10,08; 9,95; e 10,58% e a digestibilidade in vitro da matéria seca, de 50,93; 55,85; 54,56; e 54,81% para capim-elefante, papuã, sorgo e milheto, respectivamente. Houve diferença significativa no ganho de peso médio diário, que foi de 0,928; 1,054; 1,121; e 1,188 kg, para o capim-elefante, papuã, sorgo e milheto, respectivamente. Não houve diferença significativa na carga animal entre as pastagens, sendo de 1682, 1634, 1389 e 1514 kg de PV/ha, e no ganho de peso vivo, que foi de 774, 668, 570 e 640 kg de PV/ha para as pastagens de capim-elefante, papuã, sorgo e milheto, respectivamente. A utilização de pastagens cultivadas de verão, manejadas corretamente, permite altos ganhos de peso por animal e por área, constituindo-se em uma excelente alternativa para intensificar a produção de bovinos de corte.

Potencial produtivo, alterações da estrutura e qualidade da pastagem de milheto submetida a diferentes níveis de nitrogênio

Com o objetivo de estudar a produção de matéria seca (MS), eficiência de utilização, taxa de recuperação do N, densidade e qualidade de forragem, foi realizado um experimento de pastejo em milheto sob níveis crescentes de N (0, 150, 300, 450 e 600 kg/ha), em um delineamento completamente casualizado com duas repetições. Foram estudadas a densidade de forragem por estrato e total e a distribuição dos componentes lâmina foliar, colmo + bainha e material morto nos distintos estratos da pastagem (0-10, 10-20, 20-30, 30-40 e >40 cm acima do nível do solo). Utilizaram-se novilhas em um sistema de pastejo contínuo com uma oferta de 10 kg/dia de MS/100 kg PV. Para manter a oferta pretendida, foi usada a técnica "put-and-take". A produção de MS apresentou relação quadrática com os níveis de N. A taxa de recuperação e de eficiência de utilização do N mostraram relação linear negativa com as doses de N. Houve aumento na contribuição de lâminas foliares e redução no percentual de colmos + bainhas, material morto e na densidade da forragem do estrato inferior até o topo da pastagem em todos tratamentos. A adubação nitrogenada não alterou a densidade de forragem e a relação folha/colmo. A relação dos níveis de N com a porcentagem de proteína bruta das frações colmo + bainha e material morto, foi linear positiva do topo para a base da pastagem e para lâminas foliares até 30 cm de altura. A digestibilidade in vitro da matéria orgânica dos componentes foi indiferente aos níveis de N, à exceção de lâminas foliares acima de 10 cm, que apresentaram relação quadrática com as doses de N.

The value of Kikuyu foggage for overwintering dry ewes

Kikuyu (Pennisetum clandestinum) is a summer growing tropical pasture species well adapted to the Midlands of KwaZulu-Natal. Kikuyu foggage (standing hay) could play an important role in a fodder flow programme to sustain dry ewes during late winter after their lambs have been weaned in mid-winter. The potential of kikuyu foggage to supply in the feed requirements of dry ewes was evaluated over four winter periods. The foggage was obtained by closing off the kikuyu to grazing during either late January or late February. The foggage was grazed for eight weeks, from mid-July to mid-September, using either strip or continuous grazing systems. Closing off date did not significantly influence the chemical composition of the material on offer. The ewes in the different treatments lost between 4.7 and 10.3% of their initial body weight over the grazing period. In vitro digestible organic matter (IVDOM) of the foggage declined as winter progressed and was positively correlated with the body weight loss of the ewes. Foggage utilization varied between 36.7 and 43.5%, indicating a high proportion of fodder wastage. The body weight loss of the dry ewes during the grazing period suggested that kikuyu foggage in the KwaZulu-Natal Midlands was unable to sustain the body weight of the dry ewe. South African Journal of Animal Science Vol.32(1) 2002: 7-13

Equine stocking density effect on soil chemical properties, botanical composition, and species density

Equine stocking densities in New Jersey generally exceed the current regional recommendation of 0.6 to 0.8 hectares per animal for mature animals. Our hypotheses that high stocking densities under continuous grazing systems affect the composition of pastures and increase soil phosphorus concentrations were tested in a field study of 40 horse pastures. Stocking densities were grouped into four treatments. Plant data were collected in the spring and summer to determine botanical composition and plant density. Soil samples were collected in the spring to measure soil chemical properties. Averaged across stocking density in the spring, Kentucky bluegrass (Poa pratensis L.) and annual bluegrass (Poa annua L.) represented 76% of the total grass density (392 and 297 tillers m−2, respectively). Common white clover (Trifolium repens L.) was the most dominant legume with a density of 289 stems m−2. In the summer, total grass density was greatest (P< 0.02) in the highest stocking density. Densities of all species declined in the summer compared to the spring except tall fescue under the highest stocking density, which increased 24%. Soil phosphorus concentrations were affected by stocking density (P< 0.05) and exceeded optimum levels for plant growth regardless of stocking density. Species that tolerate frequent grazing dominate horse pastures in New Jersey regardless of stocking density.

Influence of Pasture Management on Soil Biological Quality

The long-term sustainability of pasture management systems, whether related to structural stability or nutrient dynamics, is dependent upon maintaining soil biological properties. This study investigates the extent to which the microbiological and biochemical properties of soil can change with season and pasture management system, including their likely value as indicators of soil quality. The experiment was conducted on a 30-ha pasture near Brandon, Manitoba. Seasonal fluctuations were observed in the soil microbial and biochemical properties. In general, these fluctuations were mainly independent of the small variations in soil organic matter content but were more closely related to soil water content. The data also suggests an impact of stocking rate and grazing system on soil microbial biomass C and on N mineralization potential. However, because duration of the investigation, limited number of replications and the high soil variability encountered, it is not yet possible to recommend any particular grazing system and/or stocking rate favorable for the maintenance of soil biological quality. The trends suggest that light, continuous grazing systems had the largest microbial biomass and nutrient mineralizing activity. DOI:10.2458/azu_jrm_v53i1_banerjee

Influence of pasture management on soil biological quality

The long-term sustainability of pasture management systems, whether related to structural stability or nutrient dynamics, is dependent upon maintaining soil biological properties. This study investigates the extent to which the microbiological and biochemical properties of soil can change with season and pasture management system, including their likely value as indicators of soil quality. The experiment was conducted on a 30-ha pasture near Brandon, Manitoba. Seasonal fluctuations were observed in the soil microbial and biochemical properties. In general, these fluctuations were mainly independent of the small variations in soil organic matter content but were more closely related to soil water content. The data also suggests an impact of stocking rate and grazing system on soil microbial biomass C and on N mineralization potential. However, because duration of the investigation, limited number of replications and the high soil variability encountered, it is not yet possible to recommend any particular grazing system and/or stocking rate favorable for the maintenance of soil biological quality. The trends suggest that light, continuous grazing systems had the largest microbial biomass and nutrient mineralizing activity.

Intensidad de pastoreo y esquema de utilización en la selección de la dieta del ganado bovino durante la sequía

Chavez SAH, Perez GA, Sanchez GE. Tec Pecu Mex. 2000;38(1)19-34. The purpose of the present study was to evaluate the continuous and rotational grazing systems under heavy and moderate grazing intensities. The study was conducted at Rancho Experimental La Campana INIFAP-SARH on a typical dormant midgrass range of Bouteloua- Aristida. Seventy-one Hereford heifers (mean weight 240 kg) were distributed in four goups as follows: Continuous grazing-Moderated (n=11); Continuous grazing-High (n=25); Rotational grazing- Moderated (n=11) and Rotational grazing-High (n=24). Moderate grazing intensities were determined according to the forage availability (60% utilization) at each paddock. Heavy intensities were determined by duplicating the carrying capacity. Botanical composition diets were different (P<0.05) between plants, grazing system-plants, stocking rate-plants, plants-periods and grazing system-stocking rate-plants. Grasses were the main component (85%) on the botanical composition of the diet, followed by forbs (8.8%) and shrubs (5.5%). Croton pottsii and Bouteloua curtipendula had the highest preference indexes. Stocking rates had more impact on diet selection than grazing systems.

PRODUÇÃO ANIMAL EM PASTAGEM DE MILHETO SOB DIFERENTES NÍVEIS DE NITROGÊNIO

O experimento foi conduzido em área da Universidade Federal de Santa Maria, RS, com o objetivo de verificar os efeitos de três níveis de adubação nitrogenada (0, 150 e 300 kg/ha de N) em pastagem de milheto (Pennisetum americanum (L.) Leeke) cv. Comum, sobre a produção animal. Foram utilizados novilhos de corte e avaliados o desempenho por animal, o número de animais.dia/ha e o ganho de peso vivo por área. O sistema de pastejo adotado foi o contínuo, com ajustes de carga para manter uma pressão de pastejo de 10%, caracterizando um resíduo médio de 3.168 kg de matéria seca/ha. As variáveis dependentes mostraram relação linear positiva com os níveis de adubação nitrogenada, o que denota o alto potencial do milheto.

Pasture Growth, Production, and Quality Under Rotational and Continuous Grazing Management

Management intensive rotational grazing (MIRG) is an expanding practice among dairy farmers in the Upper Midwest Despite the high productivity associated with MIRG pastures, many acres of unmanaged, continuously grazed pastures still exist. Our goal was to document relationships between forage growth, production, and quality in rotational and continuous grazing systems and to evaluate the role that management plays in the productivity of these pastures. Forages were monitored under farmer management on three MIRG dairy farms and on three continuously grazed pastures (CON) on conventional livestock farms in 1994 and 1995. Evaluation of the results was complicated by the range of conditions and management practices that characterized the study's participants. As is typical for this region, CON pastures in this study were unmanaged. In contrast, MIRG pastures were monitored daily by their owners and sward health was maintained through movement of the herd and such practices as interseeding legumes. Forage mass for MIRG pastures was greater than CON every week of the 24-wk grazing season, averaging 1763 lb/acre for ready-to-graze MIRG paddocks vs. 850 lb/acre for CON. Crude protein averaged 16.6% for MIRG vs. 15.3% for CON. Seasonal average ADF values were 34.2% for MIRG and 34.1% for CON. Average NDF values were 53.4% for MIRG and 56.8% for CON. Forage mass between 1300 and 1900 lb/acre appeared to provide a balance between yield and quality on MIRG pastures. Cooperating farmers most often chose to graze paddocks at this level. For CON, forage quality decreased as forage biomass increased. Ready-to-graze MIRG paddocks had significantly higher quality than CON pastures at equivalent levels of forage biomass. It was not possible in this study to isolate individual management practices and test them separately, so no one factor can be viewed as responsible for the differences we observed. Indeed, these differences probably are the result of the interaction among several management practices on MIRG farms and the lack of pasture management on CON farms.

Heterogeneity in Tall Fescue Pastures Created and Sustained by Cattle Grazing

In continuous grazing systems the amount of herbage and its quality is a matter of primary concern. However, at moderate stocking, cattle grazing usually leads to the generation of patches differing in forage quality and quantity even in virtually monospecific pastures. This patchiness influences subsequent vegetation and animal responses. We analyzed the heterogeneity created and sustained by cattle grazing in a tall fescue (Festuca arundinacea Schreb.) pasture at stocking densities ranging from 1.8 to 4.1 animals ha-1 over 2 years. Cattle grazing created and maintained a mosaic of areas with different degrees of utilization. Heavily utilized patches had less biomass per unit surface, but their live biomass was more dense and had a higher nitrogen concentration. Patch boundaries fluctuated throughout the year at all stocking densities. Patch locations were more stable at the lower stocking densities, where cattle repeatedly returned to heavily utilized patches even though they represented less than 30% of the total surface. This reinforces the idea that, at low and moderate stocking densities, cattle can obtain a nutritional benefit by patch grazing. The percentage of heavily utilized patches reached a maximum value at an instantaneous grazing pressure of approximately 0.0016 animal units kg forage-l. When this threshold is passed, animal selection between patches could be conditioned by the presence of feces or thistles, and pasture condition affected by overgrazing of the heavily utilized patches.

Tallgrass Prairie Response to Grazing System and Stocking Rate

Grazing system and stocking rate effects on standing crop of species and relative species composition of tallgrass prairies in north-central Oklahoma were evaluated from 1989 to 1993. Twelve experimental units, consisting of pastures dominated by big bluestem [Andropogon gerurdii Vitman], little bluestem [Schizachyrium scoparium (Michx.) Nash], and indiangrass [Sorghustrum nutuns (L.) Nash], were arranged in a completely randomized design with either a short duration rotation or continuous grazing system and stocking rates ranging from 51.5 animal-unit-days/ha (AUD/ha) to 89.8 AUD/ha. Yearling steers grazed the pastures from late April to late September. Cumulative precipitation was above average during the study period. Continuous and rotation grazing affected the major herbage components similarly over time. Standing crop of all major herbage components declined as stocking rate increased. The standing crop of the major herbage components also declined from the first to the last year of the study. The decrease in standing crop of big bluestem, indiangrass and forbs over years was greatest at lighter stocking rates. Relative composition of switchgrass

Average daily gain, blood metabolites, and body composition at first conception in Hereford, Senepol, and reciprocal crossbred heifers on two levels of winter nutrition and two summer grazing treatments.

Hereford (n = 48), Senepol (n = 42), and reciprocal crossbred (n = 34) heifers from two consecutive calf crops were stratified by breed, age, and BW to receive bahiagrass (Paspalum notatum) hay offered free choice and 150 mg monensin x heifer(-1) x d(-1) in addition to either 2.27 kg x heifer(-1) x d(-1) of a 75% cracked corn and 25% soybean meal mixture (CS) or .91 kg x heifer(-1) x d(-1) of soybean meal (SBM). Heifers in each treatment were divided into two winter pasture replicates and exposed to fertile bulls. In spring of each year, one-half of the heifers from each winter treatment were allotted to either a continuous (CONT) or rotational (ROTA) grazing system on bahiagrass pastures for the summer phase of the study. Heifers supplemented with CS had higher ADG from the beginning of the study to first conception than heifers fed SBM (.39 vs .31 +/- .02 kg/d; P < .01). Heifers fed CS were younger at first conception than SBM heifers (500 vs 563 +/- 32 d of age; P < .05) but had similar BW (312 vs 317 +/- 7 kg; P > .10). During the 2-yr study, a subset of Hereford (n = 12), Senepol (n = 15), and reciprocal crossbred (n = 14) heifers were subjected to urea space measurements to determine body composition at first conception. Change in body composition over time was analyzed by regression and body composition at first conception was predicted from these regressions. At first conception, percentage of empty body fat was not affected by treatment or year; however, percentage of empty body fat tended to be higher in crossbred than in Hereford and Senepol heifers (16.6 vs 14.3 and 14.4 +/- .94%; P < .10). Stepwise regression of BW, body condition score (BCS), fat thickness (determined by ultrasound), and body composition at first conception on age at first conception revealed that BCS and BW accounted for 55% of the variation in age at first conception (P < .01).

Evaluating Grazing Strategies for Cattle: Deer and Cattle Food Partitioning

We studied resource partitioning between cattle and deer (Odocoileus virginianus Boddaert) within replicated treatments of continuous and short-duration grazing at heavy and moderate stocking rates. We recorded food habits using the bite-count technique with tame white-tailed deer, and the esophageal fistula technique with steers. Through use of canonical discriminant analysis, we found diets of cattle and deer to be distinct (p< 0.05) from each other in every treatment throughout the sampling period. Overall, deer used mostly forbs (72%) whereas cattle primarily used grasses (60%) and forbs (39%). We also evaluated sensitivity to pasture conditions created by cattle grazing by comparing diets across treatments, especially during the summer months (May through September) and the second winter, which was affected by drought. Out of a possible 48 treatment combinations compared, deer selected different diets 21 times whereas cattle selected different diets 16 times. Deer were more sensitive than cattle to grazing treatments. Cattle were most sensitive to treatments during the first summer and second winter. Deer were the least sensitive to the grazing treatments during spring, when their diets were similar across all treatments. We recommend moderate stocking rates to reduce dietary overlap between cattle and deer and continuous grazing or less intensive grazing systems to create an environment where deer can select greater amounts of forbs.

Effect of grazing frequency and intensity onLolium perenneL. pastures under subtropical conditions: Herbage quality

Abstract The cellulase dry matter disappearance (CDMD) and herbage nitrogen (N) of Lolium perenne (perennial ryegrass) were evaluated for pastures grown under subtropical conditions for two years, under five combinations of grazing frequency and intensity, each applied in a rotational grazing system. These quality factors were also evaluated for a simulated continuous grazing (CG) system. Low frequency, low intensity grazing produced lower CDMD and herbage N levels than higher grazing frequencies and intensities. These differences were, however, generally small. Overall, levels of herbage digestibility (estimated by CDMD) and N fell within similar ranges to those observed for perennial ryegrass in temperate environments. Seasonal trends in quality were characterized by high levels during late autumn to early summer (May to October) and low levels during mid‐summer to early autumn (January to April). These data would tend to support high frequency grazing as part of the management programme for perennial r...