Horse Grazing Research Articles

PREFERÊNCIA DE EQÜINOS EM PASTEJO: EFEITO DA ALTURA DE DOSSÉIS DE GRAMÍNEAS DO GÊNERO CYNODON

O experimento foi conduzido no Centro de Estações Experimentais da Universidade Federal do Paraná, em fevereiro de 1998, quando as gramíneas Cynodon spp. cv Tifton 85, Cynodon nlemfuensis cv Tifton 68, Cynodon spp. cv Tifton 44, Cynodon nlemfuensis (Porto Rico) e Cynodon nlemfuensis (Estrela Roxa) foram estabelecidas em parcelas em um delineamento inteiramente casualizado com parcelas subdivididas e quatro repetições. As parcelas foram subdivididas em duas alturas do dossel (alto e baixo) caracterizadas pela diferença de altura das plantas. Os tratamentos foram ofertados a três éguas por duas horas em cinco dias consecutivos. A preferência entre os tratamentos foi identificada pela avaliação do número de bocados e pela desfolha nas unidades vegetativas marcadas nas parcelas e alturas. A profundidade do bocado foi quantificada por meio da identificação da altura do perfilho estendido e da menor altura pastejada nos perfilhos marcados das diferentes gramíneas. A Tifton 85 foi preferida, seguida pela Coastcross 1, Tifton 68 e Tifton 44. A Estrela Roxa e a Porto Rico foram preteridas. As gramíneas de maior preferência apresentavam maior massa de folhas verdes em relação à massa de colmos (P

Use of Remote Sensing Techniques to Determine the Effects of Grazing on Vegetation Cover and Dune Elevation at Assateague Island National Seashore: Impact of Horses

The effects of grazing by feral horses on vegetation and dune topography at Assateague Island National Seashore were investigated using color-infrared imagery, lidar surveys, and field measurements. Five pairs of fenced and unfenced plots (300 m2) established in 1993 on sand flats and small dunes with similar elevation, topography, and vegetation cover were used for this study. Color-infrared imagery from 1998 and field measurements from 2001 indicated that there was a significant difference in vegetation cover between the fenced and unfenced plot-pairs over the study period. Fenced plots contained a higher percentage of vegetation cover that was dominated by American beachgrass (Ammophila breviligulata). Lidar surveys from 1997, 1999, and 2000 showed that there were significant differences in elevation and topography between fenced and unfenced plot-pairs. Fenced plots were, on average, 0.63 m higher than unfenced plots, whereas unfenced plots had generally decreased in elevation after establishment in 1993. Results demonstrate that feral horse grazing has had a significant impact on dune formation and has contributed to the erosion of dunes at Assateague Island. The findings suggest that unless the size of the feral horse population is reduced, grazing will continue to foster unnaturally high rates of dune erosion into the future. In order to maintain the natural processes that historically occurred on barrier islands, much larger fenced exclosures would be required to prevent horse grazing.

Equine forages and grassland management

There are about 900,000 horses kept in the UK for leisure and a further 65,000 kept professionally (British Horse Society, 2003). Altogether about 800,000 ha are utilised for grazing and feeding horses, making the equine industry the second largest in the UK land based sector, after agriculture. The purpose of this paper is to review the present information on the management of grassland for horse grazing and for conserved forage, to identify some current issues and to postulate some areas for future research and development.Maximizing the contribution made by grazing to the nutrition of the horse is a reasonable goal if economy is the main priority. Even if this is not the case, horses have a need to satisfy their natural instinct to graze. The deterioration of poorly managed grassland associated with equine enterprises is well documented (Odberg and Francis–Smith, 1976, and Judd et al., 2001). Horse grazing differs from grazing by cattle and sheep, in particular in the way that they select species and in the spatial pattern of their grazing.

An environmental narrative of Inland Northwest United States forests, 1800–2000

Fire was arguably the most important forest and rangeland disturbance process in the Inland Northwest United States for millennia. Prior to the Lewis and Clark expedition, fire regimes ranged from high severity with return intervals of one to five centuries, to low severity with fire-free periods lasting three decades or less. Indoamerican burning contributed to the fire ecology of grasslands and lower and mid-montane dry forests, especially where ponderosa pine was the dominant overstory species, but the extent of this contribution is difficult to quantify. Two centuries of settlement, exploitation, management, and climate variation have transformed the fire regimes, vegetation and fuel patterns, and overall functionality of these forests. We present a narrative that portrays conditions beginning at the first contact of Euro-American settlers with Indoamericans of the region and extending to the present. Due in part to its geographic isolation, the Inland Northwest was among the last regions to be discovered by Euro-Americans. In 200 years the region has undergone fur trapping and trading, sheep, cattle, and horse grazing, timber harvesting, mining, road construction, native grassland conversion to agricultural production, urban and rural area development, fire prevention, and fire suppression. We highlight key changes to forest landscape patterns and processes that occurred under these combined influences, discuss implications of the changes, and progress towards restoring sustainability. An adaptive ecosystem management model has been adopted by public land management agencies to remedy current conditions. Ecosystem management is a relatively new concept that emphasizes the integrity and sustainability of land systems rather than outputs from the land. Adaptive management emphasizes the twin notions that incomplete knowledge and high degrees of risk and uncertainty about earth and climate systems will always limit land and resource planning and management decisions, and that management is chiefly a learning and adapting process. We discuss current issues and future options associated with ecosystem management, including the low likelihood of social consensus concerning desired outcomes, the lack of integrated planning, analysis, and decision support tools, and mismatches between existing land management planning processes, Congressional appropriations, and complex management and restoration problems.

The influence of grass height on bite dimensions of horses

The management and maintenance of swards grazed by horses is known to be a difficult task. In a short period of time (2 to 3 weeks) pastures used for horse grazing develop patches of bare ground, short grass and areas which horses refuse to graze because of faecal contamination. Bite depth and bite area are important in determining the effects of grazing on the vegetation. The dimensions of the bite have been investigated in cattle (Ungar et al., 1999), sheep and goats (Concha, 2000), but not horses. The interaction of the horse with the pasture surface is poorly understood but important to improve management and maintenance of areas grazed by horses. The study reported examines the influence of grass height on bite dimensions, i.e. bite depth, bite volume and bite area of the horse at grazing.

Cattle, mining or fire? The historical causes of recent contractions of open forest in the wet tropics of Queensland through invasion by rainforest

Changes to Aboriginal fire regimes since European occupation are thought to have affected the range and demographic structure of many vegetation communities. This study shows a contraction by 49% of the area of fire-prone open forest through rainforest invasion between 1945 and 1991-94 in the northern wet tropics of Queensland, Australia. Relative Growth Rates (RGR) for open forest areas varied from -0.112 to -0.005. Collaborative historical research with the Aboriginal traditional owners, the Kuku-Yalanji people, investigated possible linkages with alterations to their fire practices. A multiplicity of human impacts is associated with the measured vegetation change, including clearing for agriculture and mining, logging for timber and firewood, and the introduction of cattle and horses. Some rainforest expansion since 1945 represents a recovery following clearing from earlier mining operations. Contraction of open forest through rainforest invasion was most rapid (RGR = -0.124) where there was a continuation of Aboriginal fire management with cattle grazing. The contraction of open forest was nine times slower in an ungrazed area (RGR = -0.005) than in a nearby area grazed by horses (RGR = -0.045). Aboriginal fire regimes may act synergistically with cattle or horse grazing to accelerate the invasion of rainforest into open forest. Management prescriptions currently focus on active fire management to prevent further open forest contraction. However, fire management may have unexpected outcomes when rainforest-open forest dynamics are complicated by recent historical factors such as cattle grazing, logging, and tin mining, and possible synergies between these factors and fire regimes. Managers need to understand the histories of particular sites when formulating plans, and monitor the consequences of their actions to enable an adaptive approach.

Horse grazing effects on semi-natural grassland landscapes established on the coastal terrace in eastern Hokkaido

Horse grazing effects on semi-natural grassland landscapes established on the coastal terrace in eastern Hokkaido

Properties of herbage in relation to equine dysautonomia: biochemical composition and antioxidant and prooxidant actions.

To investigate the etiology of equine dysautonomia (ED), a degenerative polyneuropathy affecting grazing horses, the biochemical composition and antioxidant/prooxidant activities of aqueous extracts of plants collected from ED pastures were determined. Plants collected immediately after an outbreak of ED had reduced antioxidant and weak prooxidant activities when compared with control plants (plants collected from ED pastures out of ED season and control plants from ED pastures that were grown under favorable conditions). ED plants also had significantly increased concentrations of fructose and low molecular weight phenolic compounds, significantly more of one amino acid zone (probably valine), significantly less tartaric acid, and a nonsignificant decrease in ascorbic acid content when compared with control plants from ED pastures that were grown under favorable conditions. These findings suggest that ED plants may be under oxidative stress, possibly due to chilling, drought, or fungal colonization. However, experimental drought and chilling of plants did not reproduce the biochemical alterations identified in ED plants. It is possible that the altered biochemical content of ingested plants may contribute, directly or indirectly, to the development of ED in grazing horses.

Farmers' perception of land-cover changes in NE Iceland

Land degradation is considered to be a major environmental problem by scientific and political institutions in Iceland. In past years, land degradation problems related to sheep and horse grazing have gradually come to the fore in public discussion of environmental questions. However, land degradation is often evaluated in different ways by different groups of people. This has led to a lack of consensus regarding rates and severity of land degradation. Therefore, it is important to study differences in environmental perception, and how these differences can be dealt with in the context of sustainable management. This paper aims to highlight farmers' perception of land degradation in Iceland, as perceptions of the environment determine the basis for human activities related to the land. A total of 100 farmers in NE Iceland were questioned and interviewed for their opinions on land degradation, its history, causes and severity. The results indicate that farmers consider land degradation to be a slow process, and not a catastrophic phenomenon. The understanding of the general ecological processes by the users affects their practices and concern for their environment. This feeds back on the land-use system and ultimately causes changes in land-cover. Therefore, if we are to increase our understanding of the processes that lead to land-cover changes we have to integrate the perceptions of land users and technical experts. In this way we may improve conservation practices and land-resource management policies. Copyright © 2000 John Wiley & Sons, Ltd.

Peace and War: Reminiscences of a Life on the Frontiers of Science

This work is the memoir of one of the key scientists involved in the atomic bomb and the chief research assistant and intimate friend of J. Robert Oppenheimer. A prominent member of the Manhattan Project, Robert Serber was one of a team of scientists who assembled the bombs on Tinian Island for transport to Hiroshima and Nagasaki. He was also one of the first Americans to walk among the Japanese ruins after the catastrophe. Written with science historian Robert P. Crease, this self-portrait is the story of Serber's life before, during and after World War II. It brings into focus the leading figures and events during this period in American science. Serber tells of his wartime experiences at Tinian Island and in Japan, in letters to his wife Charlotte, herself a key player at Los Alamos and the only female group leader there. These letters depict what Serber saw, such as the rows of iron office safes protruding from the rubble of Hiroshima, and the grazing horse whose hair had been scorched on one side by the fireball but was untouched on the other. Serber is also eloquent about the troubles he faced as a result of his refusal to take part in public debate about the morality of his wartime work; how his opposition to rapidly developing the hydrogen bomb earned him the enmity of Edward Teller and others; and how he was investigated and his security clearance challenged, several years before Oppenheimer's. Serber also recounts stories involving Oppenheimer, Murray Gell-Mann, Ernest O. Lawrence and Edward Teller.

Effects of First-last Grazing of Cattle and Horses on their Grazing Behaviour and Vegetation of Improved Pastures

Effects of First-last Grazing of Cattle and Horses on their Grazing Behaviour and Vegetation of Improved Pastures

Populousness changes of a Pampas Silvopastoral System (Argentina) as a function of tree canopy

The aim of this research was to assess the effects of total and partial clearing and alternate grazing on succession changes of a Silvopastoral System. The experimental area is located in the State of Buenos Aires, Argentina (34º 52' LS; 58º 08' LW). At the initial time the vegetation tree appeared to be predominantly Honeylocust (Gleditsia triacanthos L.), which represented 90 p. 100 of cover. The native vegetation mainly composed by rescue grass (Bromus catharticus Vahl.) and Italian ryegrass (Lolium multiflorum Lam.), represented 4,5 p. 100 of the basal cover. During ten years, from 1985 till 1994, data were collected to describe differences between cleared and woodland areas. The treatments were subjected to a continous and noncontinous horse grazing (with distubance and resting events). Our results suggest that partial clearing and alternate grazing does not alter tree density. Furthermore, this treatment may result in a greater (p < 0.05) forage cover (23 p. 100), species diversity (2.5) and a higher nutritive value and forage biomass production (2,020 kg of dry matter/ha-1).

Recovery of a High Elevation Plant Community after Packhorse Grazing

We evaluated the impact of packstock grazing on a dry, upper timberline meadow. Horses were picketed on 15 m ropes for different durations, months, and frequencies over 3 summers. Before horse grazing, we estimated vegetal, bare soil, litter, rock, and moss cover, measured grass and forte plant heights, counted grass and forte stems per area, and determined the percent of plants grazed. These measurements were repeated 1 growing season later. More bare ground and less litter and vegetal cover were recorded 1 year following single 8- or 18-hour grazing events. Single grazing events of 4-hour duration had no effect on cover. Decreases in vegetal cover were associated with reduced stem numbers. Eighteen hour picket durations reduced subsequent year production of grass and forte stems. We discuss the difficulties encountered in this study, including estimates of necessary sample sizes, to help in the design of future studies.

17. Horse grazing in northern Iceland — behaviour and habitat selection : J. Magnússon and A.G. Thorhallsdóttir. Hvanneyri Agricultural College, IS-311 Borgarnes, Iceland

17. Horse grazing in northern Iceland — behaviour and habitat selection : J. Magnússon and A.G. Thorhallsdóttir. Hvanneyri Agricultural College, IS-311 Borgarnes, Iceland

Horse grazing under cold and wet conditions: a review

This review paper summarises information on some aspects of horse grazing with special reference to areas where summer temperature is limited, winters are cool or cold, and precipitation is generally high. Due to their excellent ability to utilize herbage of variable quality with a high fibre content, horses are well-adapted to grazing a range of plant species and pasture types. Although grasses are the most preferred species by horses, several other vegetation species are eaten depending on factors such as season and grazing intensity. Horse growth rates compare favourably with those of other livestock species, even when they were grazed on poor quality pastures, such as mires. The ability to accumulate much body fat in summer, which can be mobilized as a source of energy in winter, is of great importance in free-ranging horses. Mixed grazing of horses with sheep and/or cattle may lead to improved grassland management, both from ecological and economic points of view.

Impacts of Mule Deer and Horse Grazing on Transplanted Shrubs for Revegetation

Revegetation success on foothill ranges in northern Utah using big sagebrush (Artemisia tridentata Nutt. spp. wyomingensis Beetle and Young) and rubber rabbitbrush brush (Chrysothamnus nauseosus Britt. spp. albicaulis H. and C.) was determined as influenced by winter mule deer browsing and spring horse grazing. Treatment areas of 0.1 ha with 3 replications included a protected control, use by deer only, use by horses only, use by deer and horses, and use by deer with horse grazing delayed for 3 years after seedling transplant. Results from the first 6 growing seasons following transplanting of seedlings showed grazing by horses only tripled the available, per-plant browse production of big sagebrush compared to protected plots, whereas browsing by deer only resulted in a 40% decrease in browse production. Seedling survival of big sagebrush differed between treatments during the first 3 growing seasons but was not affected by grazing after the third growing season. Rubber rabbitbrush was not affected by treatments.

Land Use Change and its Characteristics in the Auckland City's Countryside, New Zealand

In this paper the author clarifies the sequence of land use change in the Auckland city's countryside and analyses it at micro-scale using the example of Clevedon area, Manukau City. Clevedon area is situated around the built-up area of Auckland and is everywhere zoned for rural land use. In this area definite changes agricultural land use to urban land use are not apparent, but agricultural use changes to other agricultural one in terms of function and quality. Three sequences of land use change based on competition between agricultural and urban uses and land use policy of the Manukau City Council are recognisable; before 1969, 1970 to 1983, and after 1984.In the 1970s and early 1980s a trend from dairy farming to beef farming and from sheep and beef farming to more specialised beef farming was apparent in the framework of traditional pastral farming. Dairy farming remained important during this period with changing ownership of land and changing location of town milk production but the less labour intensive beef farming became attractive with decreasing agricultural labour force. New Zealand pastoral farming permits such changes in livestock specialisation as the system is very flexible and not capital intensive. In fact these trends could be reversed with fluctuations of milk and meat price.In the 1980s land use change was characterised by various farms of horse raising and horticulture, and in some areas traditional pastoral uses, occupying former dairy and cattle farms. These changes had not been evident in the previous period, and the rural land use zoning encouraged them, but the trend to horse raising and horticulture became stronger in this period. The grazing of horses was associated with the purchase of rural land by other farmers and with the growing importance of the commercial blood stock and racing industry in South Auckland. The horticulture based on using labour, land and capital more intensively, and it is developed in Rural Two zone where fruit growing have priority. Availability of small parcels of land in the rural zone originating in previous periods, increasing property taxes as land values increased, and much demand for high profitability of rural land, contributed to the changes in the function of agricultural land use. In the 1980s the sequence of agricultural land use change is uni-directional. Reversion to the traditional pastoral farming of the area is not an option. Thus, in comparison with the earlier period a feedback sequence is not included in model.

Spatial patterning of sweet briar (Rosa rubiginosa) by two vertebrate species

AbstractThe dispersal and spatial patterning of sweet briar (Rosa rubiginosa) by pied currawongs (Strepera graculina) and horses (Equus caballus) on the southern tablelands of New South Wales was investigated. These two vertebrate species eat the sweet briar fruits and disperse them in a viable condition. The spatial patterns of horse faeces and pied currawong pellets were shown to correspond to the patterns of sweet briar in paddocks which had one of these vertebrate species present. Paddocks with a history of horse grazing but with no large roosting trees had sweet briar populations which were distributed almost randomly; in paddocks never grazed by horses but with roosting trees there was a strong aggregation of sweet briar under trees. These spatial patterns were additive in paddocks with a history of both horse grazing and large trees. Such structuring of vegetation by vertebrates is discussed as an alternative hypothesis to be considered when interpreting ecological processes from spatial patterns.

Explosive speciation at the base of the adaptive radiation of Miocene grazing horses

Adaptive radiations are generally considered to be periods of rapid evolutionary change1. Simpson2 viewed rates of evolution as either taxonomic or morphological and various methods for their quan-tification are widely used1,3–5. In contrast to classic studies of extant organisms6–7, adaptive radiations of fossil groups are usually analysed on the superspecific (for example, generic or familial) level. But relatively few studies have dealt with the patterns and processes of adaptive radiations for fossil species. The principal adaptive radiation of grazing horses occurred in North America 15 to 18 million years ago (Myr BP), when at least 19 species originated by cladogenesis. We report here that the pattern of horse taxonomic evolution is logistic, with very high origination rates observed early during the radiation. By 15 Myr BP diversity reached a plateau of about 16 contemporaneous grazing species, and this taxonomic carrying capacity continued until about 6 Myr BP. In contrast, rates of morphological (dental) evolution during the period were 'normal' (or holotelic) relative to other known fossil groups. Thus, adaptive radiations are times of rapid cladogenesis, but not necessarily rapid morphological change.

Simulation and Management Implications of Feral Horse Grazing on Cumberland Island, Georgia

Cumberiand Island National !&shore, Georgia, is inhabited by a population of feral horsea that intensively graze the island’s salt marshes. Based on 18 months of experimental grazing studies, a carbon flow simulation model was developed for a medium height Spartina a&emfloru marsh and used to estimate an acceptable population size of feral horses. Five-year shnulations indicated a threshold of 2,700 kg/ha aboveground Spurtha biomass below which the system did not recover if intensive grazing continued. The difference between this threshold and annual peak biomazs of ungrazed Sparth was used to estimate horse densities that would not cause marsh degradation. Results suggest the horse population should number between 49 and 73 horses if exceesive damage to the salt marshes is to be prevented. Thus, the current population of 180 horses should be reduced.