Changes In Pasture Composition Research Articles

Botanical composition gradients in silvopastoral systems on temperate native grasslands of Uruguay

AbstractSilvopastoral systems may provide important production and environmental benefits. The loss of cool-season (C3) grasses from temperate grazed native grasslands is associated with selective grazing and excessive solar radiation that limit their survival. Silvopastoral systems integrate trees with grasslands that provide shade to both cattle and herbaceous plants, potentially favoring C3 species. There is limited information about the effect of trees on the species and functional composition of native grasslands in the Campos biome in South America. The objective of this study was to detect gradients in the botanical composition of grasslands as affected by changes in the shade associated with distance to the trees and cardinal orientation in three situations defined by the combination of soil and tree species (Prosopis on Solonetz, Acacia on Brunisols, and Eucalyptus on Brunisols). Soil cover of the herbaceous species under trees was recorded in double transects located in the four cardinal directions. In all situations there were changes in pasture composition in the different shaded regions (total shade, partial shade, or full sun). Under the canopy, there was an increase of cool-season grasses such as Bromus catharticus Vahl, Lolium multiflorum Lam., Stipa hyalina (Nees) Barkworth, and S. setigera J.Presl. At greater distances from trees, cover of warm-season grasses, such as Axonopus affinis Chase and Paspalum notatum Flueggé increased. These gradients suggest that trees in silvopastoral systems can increase the abundance of cool-season species and potentially improve the forage nutritive value of the native pasture.

A survey comparing regeneratively and conventionally managed pastures and farm management policies

A pasture and farm management survey was conducted on thirteen geographically paired regenerative and conventional beef and sheep farms in the upper North Island to identify differences in pasture attributes and management practices. Farms were paired by geographical location and livestock type. When compared to conventional pastures, regenerative pastures had a similar number of grass, legume and broadleaf species (averaging 4, 1 and 3 species respectively), three times as much legume (13 compared to 4% content) and 30% less perennial ryegrass in total DM (P<0.01) but a similar broadleaf content. There was no difference between pasture types in pre- or post-grazing covers. Compared to conventional pastures, soils sampled from regenerative pastures had a higher pH, and herbage had higher levels of calcium, boron, molybdenum (P<0.05) and a trend towards lower Olsen P values (P=0.052). There was a divergence between farm types in fertiliser policies, with regenerative farmers generally not using synthetic nitrogen (N) and phosphorus (P) products and applying a wider range of nutrients. Herbicides and pesticides were used across both farm types. Changes in pasture composition (i.e., less perennial ryegrass and more clover) and soil nutrient status were consistent with lower N and P inputs on regenerative farms.

Functional Classification of Feed Items in Pampa Grassland, Based on Their Near-Infrared Spectrum

Native pastures that present high botanical richness produce a variety of feed items for grazing herbivores. Diet selection takes place at the bite scale and, at a daily scale, the sum of bites composing the intake determines diet characteristics. The objective of this paper is to bring an original contribution to the understanding of diet selection in diverse foraging environments such as native Pampa grasslands. The issues are 1) to improve grazing management in Pampa ecosystems and 2) to evaluate the ability of native pastures to feed a herd in order to reduce supplementation and to improve the economic sustainability of extensive systems. We hypothesize that the information contained in the infrared spectra of plant samples corresponding to potential bites can be useful for establishing functional bite categories, which, in turn, can be used to understand and manage pastoral ecosystems. We analyzed the near-infrared spectrum (NIRS) of 1 515 bite samples gathered in 2012 using the continuous bite monitoring method applied to heifers continuously grazing on Pampa grassland at five grazing intensities (randomized block design with two replicates, applied since 1987). On the basis of the main wavelengths, a statistical classification of bite samples was produced and five classes were described: 1) small bites of wetland grasses and short grass; 2) medium bites of forbs and short grass; 3) small bites of short Poaceae and mixed species; 4) large bites on tussocks of Poaceae; and 5) extralarge bites on stiff tussock of Poaceae and Apiaceae. In order to evaluate the functional value of the classification, we tested its ability to take seasonal changes in pasture composition into account and to describe the variations in animal intake and performance in contrasted grazing conditions. We concluded that the NIRS is a good support for establishing functional classes of feed items that can be used to understand the foraging behavior and diet composition of grazing herbivores. Our approach was tested in Pampa grasslands grazed by cattle but should be applicable to a wide range of ecosystems, provided that chemical composition is more relevant for selection than feed item accessibility.

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.

Pasture production and composition response after killing Eucalypt trees with herbicides in central Queensland

Clearing woodlands is practised worldwide to increase crop and livestock production, but can result in unintended consequences including woody regrowth and land degradation. The pasture response of two eucalypt woodlands in the central Queensland rangelands to killing trees with herbicides, in the presence or absence of grazing and regular spring burning, was recorded over 7 or 8 years to determine the long-term sustainability of these common practices. Herbage mass and species composition plus tree dynamics were monitored in two replicated experiments at each site. For 8 years following herbicide application, killing Eucalyptus populnea F. Muell. (poplar box) trees resulted in a doubling of native pasture herbage mass from that of the pre-existing woodland, with a tree basal area of 8.7 m2 ha–1. Conversely, over 7 years with a similar range of seasons, killing E. melanophloia F. Muell. (silver-leaved ironbark) trees of a similar tree basal area had little impact on herbage mass grown or on pasture composition for the first 4 years before production then increased. Few consistent changes in pasture composition were recorded after killing the trees, although there was an increase in the desirable grasses Dichanthium sericeum (R. Br.) A. Camus (Queensland bluegrass) and Themeda triandra Forssk. (kangaroo grass) when grazed conservatively. Excluding grazing allowed more palatable species of the major grasses to enhance their prominence, but seasonal conditions still had a major influence on their production in particular years. Pasture crown basal area was significantly higher where trees had been killed, especially in the poplar box woodland. Removing tree competition did not have a major effect on pasture composition that was independent of other management impositions or seasons, and it did not result in a rapid increase in herbage mass in both eucalypt communities. The slow pasture response to tree removal at one site indicates that regional models and economic projections relating to tree clearing require community-specific inputs.

Sustainability of high‐country pastures under contrasting development inputs. 9. Vegetation dynamics

Changes in pasture composition over 24 years are reported for two grazed multiple‐species mixture trials on a high‐country soil. Quantified response equations (34) between different plant species ranking, vegetation types, time, fertiliser and grazing input treatments for 19 years are reported depending on whether estimation is of “species from environment” (species response from treatment variables) or “environment from species” (treatment variables from species composition). Species abundance and vegetation type were primarily determined by S and P fertiliser levels, duration of development, and only secondarily by relative stocking rate or grazing method. Species dominance and vegetation continued to change over time. Lupinus polyphyllus was dominant over most of the period at low fertiliser input levels, while Trifolium ambiguum increased steadily to dominate in the higher fertiliser input levels during the second decade, with both as sustainable pasture species options.

Stability, resilience and sustainability in pasture-based grazing systems

In this paper we employ a simple dynamic simulation model to illustrate and extend the pasture envelope concept as an approach to characterising the stability, resilience and sustainability of pasture-based beef grazing enterprises. The pasture envelope is a form of phase diagram in which the trajectories over time of key biophysical variables such as pasture biomass and composition are graphed against critical thresholds established on the basis of pasture growth rates and livestock growth requirements. We extend the concept to incorporate key financial variables such as cash flow and critical financial thresholds. The model simulates a steer fattening enterprise based on a phalaris and sub-clover pasture in the Northern Tablelands of New South Wales, Australia. The model incorporates pasture growth and senescence for the two pasture species with competition between the species for soil nutrients and light, preferential grazing of the two species by the livestock with livestock growth based on pasture consumption. The model incorporates a variety of decision rules for rotating livestock among multiple paddocks. The model did not simulate changes in soil nutrients. Scaling the seasonal growth pattern of the pasture species captured the influence of rainfall and temperature on pasture growth. Two sets of simulations were run to illustrate the use of the pasture envelope concept to explore the economic and biological stability and resilience of the pasture system. The first set was designed to explore the financial and biological stability of the enterprise and involved simulating the impact of different stocking rates and rotation period on pasture production and composition, and cash flow. The second set of simulations was designed more to explore the resilience of the enterprise and involved introducing shocks to the enterprise in the form of `droughts' of varying strengths. This was achieved by, for example, reducing the maximum growth rate for both pasture species by 50% but maintaining the same seasonal pattern in the maximum growth rates of each species. The first simulation showed that at low stocking rates the enterprise was biologically stable, but cash flow was also low. Increasing stocking rates increased the cash flow, but also reduced the biological stability of the pasture until at very high stocking rates the pasture system collapsed. Changing the rotation period also affected the stability of the enterprise. In situations where the rotation period was very long, greater than 120 days (or 20 days/paddock), the biological system became unsustainable due to detrimental changes in pasture composition. The enterprise was somewhat resilient to drought at stocking rates less than 1 steer/ha. At stocking rates of 1 steer/ha, the enterprise was economically and biologically unsustainable in moderate or severe droughts. At a stocking rate of 1.25 steers/ha, the enterprise was unsustainable for droughts of any severity.

The effects of sodium and potassium fertilizers on the grazing behaviour of dairy cows

Sodium fertilizer has been observed to increase the grazing time of dairy cows kept on pastures of restricted availability, but it is unclear whether this is a behavioural response to changes in pasture composition or whether it is an indirect effect of a reduction in herbage availability caused by increased cow production and appetite. Sodium fertilizer was applied in an experiment utilising tall pasture and low stocking rates so that availability would not be restricted. Cows on the pasture with sodium fertilizer still had longer grazing times than those on pasture where no sodium fertilizer had been applied. They had more feeding bouts but bout length was reduced, and they had faster biting and walking rates while grazing. They ruminated for longer, with a faster chewing rate, and spent longer standing idle and less time lying idle. They had longer drinking bouts but a similar number of them, compared to the cows on pasture without sodium. The fixed and variable energy costs of grazing and drinking bouts were estimated, these being the energy requirements for activities that are independent and dependent of bout duration, respectively. It is proposed that for grazing bouts the low ratio of fixed costs (getting up and lying down) to variable costs (standing and walking) favoured an increase in bout number to increase the grazing time of cows grazing pasture fertilised with sodium. For drinking bouts, the high ratio of fixed costs (getting up, lying down, standing and walking to the trough) to variable costs (standing at the trough) favoured bout elongation to increase the drinking time of cows grazing pasture fertilised with sodium. A second experiment with unrestricted herbage availability between morning and afternoon milking compared the grazing response to sodium and potassium fertilizers with a control where no fertilizer was applied. Grazing time was increased most by sodium and a smaller response occurred with potassium. The proportion of herbage that was rejected by the cows decreased with sodium and to a lesser extent potassium. It is concluded that changes in herbage composition with sodium fertilizer increase feeding and drinking by the grazing dairy cow, with the increase in feeding being achieved by increased bout number but reduced bout length, and the increase in drinking being by increased bout length.

The Need for a New Approach to Grazing Management - Is Cell Grazing the Answer?

With any grazing method, the grazing pressure applied to an individual plant is a site, stock density and time dependent variable and the diet selection hierarchy of grazing animals is to the disadvantage of the most palatable and actively growing pasture components. The greater the differences in palatability and abundance among the components of a sward, and the lower the stock density, the greater the variation in the grazing pressure exerted. These effects are heightened when animals are set-stocked under adverse environmental conditions. This paper reports the comparative effects of cell grazing and continuous grazing on pasture composition on three properties on the Northern Tablelands of New South Wales. The basal diameters, relative frequency and contribution to dry weight of the most desirablelpalatable species at each site were found to remain constant or to increase under cell grazing, while declining significantly under continuous stocking. The converse was true for the least palatable components of the pasture, which declined significantly under cell grazing but changed little under continuous grazing. Percentage ground cover was significantly higher after two years of cell grazing than under continuous grazing. These changes in pasture composition may have long-term benefits with respect to erosion control, nutrient cycling, hydrological function and the stability of animal production at the cell grazed sites.

Persistence of dryland pasture species in mixed swards in Canterbury

Changes in dryland pasture composition were monitored over 5 years in pastures that were managed under a normal sheep farm management system. Grass grub population built up with time and appeared to be the main reason for plant loss and the resultant changes in pasture composition. Grass grub densities in ryegrass mixtures increased to a high level (220/m* ) by year three, with subsequent ioss of ryegrass plants. Grub densities increased more slowly in cocksfoot-, tall fescueand phalaris-based pastures, with no apparent loss of plants. Cocksfoot dominated pasture composition by year three, even when sown at only 25% of total seed mix. Phalaris did not increase its contribution and at no stage made a significant contribution to production when sown in mixtures with other grasses. As grass grub numbers declined there appeared to be some regeneration of the ryegrass component. The more persistent cocksfoot and tall fescue pastures increased their herbage yield advantage over ryegrass pastures with time. Autumn animal performance was directly related to the amount of green herbage on offer. Keywords: Costelytra zealandica, Dactylis glomerata,dryland pastures, Festuca arundinacea, Lolium perenne, Phalaris aquatica, pasture composition

Liveweight changes of sheep grazing a range of herbage allowances underPinus radiata agroforestry regimes

A range of improved pasture herbage feed allowances (1 to 5 kg dry matter/head/day) were offered to young sheep, grazing underPinus radiata grown at 0, 50, 100 and 200 stems per hectare. Six trials were conducted, each for 30 days duration between spring 1986 and autumn 1988, at tree age 13–15 years. Mean liveweight gain over all trials for 0 (open pasture), 50, 100 and 200 stems per hectare were 170, 155, 136 and 94 g/sheep/day, respectively. Liveweight gain increased curvilinearly with increasing pasture allowance at all tree stockings and tended to level off above 3 kg green dry matter/head/day. Green matter pasture in vitro digestibility of the ‘green’ pasture fraction changed little with increasing tree stocking despite changes in pasture composition. Pine needle accumulation under the higher tree stockings depressed the quality of the total feed on offer. Livestock performance under low tree stocking agroforestry regimes can be satisfactory, providing pasture management encourages fresh nutritious feed.

The long‐term effects of a range of pasture treatments applied to three semi‐natural hill grassland communities.

AbstractFive pasture treatments were applied to three semi‐natural hill grassland communities. The pasture treatments were: (1) controlled grazing, (2) controlled grazing + lime, (3) controlled grazing + lime + phosphate, (4) controlled grazing + lime + phosphate + oversown white clover and (5) controlled grazing + lime + phosphate + oversown white clover + oversown perennial ryegrass. The communities were dominated by Agrostis/Festuca (site 1), Molinia (site 2) and Nardus (site 3). The Nardus at site 3 was substantially reduced by herbicide before treatments were applied. All treatments were grazed simultaneously by mature wether sheep on three occasions each year to a residual herbage mass of 560 kg DM ha−1. There were two grazing periods, each of 4 weeks duration, beginning in mid‐May and mid‐July respectively and a further grazing period of 3 weeks duration beginning in mid‐October. The number of sheep grazing days and liveweight gain of sheep were recorded during each grazing period for 13 years at each site. Organic matter intake (OMI) and digestibility (OMD) of ingested herbage were measured in years 2, 5 and 13.Mean daily OMI per head ranged from 1290 g for treatment 1 to over 1400 g for treatments 4 and 5. OMI values were higher for the Agrostis/Festuca site (mean OMI 1450 g) than for the Molinia and Nardus sites (1310 g and 1370 g respectively) largely owing to differences in the values for treatments 1, 2 and 3. OMI values for each treatment decreased by around 300 g between May and October.Mean OMD values from treatments 1, 2 and 3 were higher for the Agrostis/Festuca site (0·66) than for the Molinia and Nardus sites (0·63 and 0·64 respectively). The OMD values for treatments 1, 2 and 3 at the Molinia and Nardus sites declined by between 0·05 and 0·02 between years 2 and 13 and also showed the greatest decrease between May and October (0·08). OMD values for treatments 4 and 5 (0·67 and 0·69 respectively) were higher than for treatments 1, 2 and 3 at all sites and levels were maintained over 13 years.Individual liveweight gains of sheep increased from treatment 1 (−18 g d−1) to treatment 5 (82 g d−1), but they decreased over time on all treatments.The Agrostis/Festuca site gave 17% more annual sheep grazing days than the Molinia site and 33% more than the Nardus site. The mean number of annual sheep grazing days for each treatment ranged from 2250 for treatment 1 to 3640 for treatment 5. Annual sheep grazing days increased over 13 years by between 35 and 45% for treatment 1 and 55 and 70% for treatment 5.The results are described in relation to the changes in pasture composition and herbage accumulation.

A Comparative Study of Sheep Grazing a Semi-Arid Saltbush Pasture in Two Condition Classes.

Measurements were made of the wool growth, body weight gain and diet of sheep grazing a saltbush pasture near Broken Hill, N.S.W. The experiment utilized a fenceline contrast in saltbush (Atriplex vesrcarra) density that was visible on Landsat imagery. It ran for five years (1976-1981) with a design of two pasture types by two stocking rates. Fleece weights varied from 3.9-6.0 kg/head and wool production from 0.6-2.9 kg/ha. Neither wool production per head nor bodyweight were substantially affected by stocking rate or pasture type. The composition and quality of the diets selected by sheep on both pastures were identical and of high nutritional value indicating their capability to accommodate differences in pasture composition. Pasture quality was not limiting between stocking rates or determined by the abundance of saltbush. Changes in pasture composition resulting from grazing and exclosure were small and of no significance.

Productivity and management of western Queensland's rangelands.

This article provides a brief description of the environment of western Queensland, and details of management practices employed by graziers to economically produce meat and wool. Changes in pasture composition occasioned by grazing pressure and difference? in annual rainfall are given. Whereas Mitchell grasslands are stable, and only affected in the short-term by the usual vagaries ofweather and stock-imposed stres?, mulga rangelands are unstable, and in a continual state of flux. Stock management, timber density and weather are each, separately or combined, liable to effect changes in floristics and consequently in animal productivity. While Mitchell grass and mulga rangelands together cotnprise the bulk of Queensland rangelands, other rangelands are also discussed including those dominated by spinifex, eucalypt woodlands, gidgee and chenopod shrublands.

Control of grass grub (Costelytra zealandica(White)) by heavy rolling

Abstract The use of an experimental roller on pasture produced up to 61% control of grass grubs, 44% higher pasture production in spring, and minor but beneficial changes in pasture composition. These results were similar to those caused by diazinon insecticide. However, only the combined effects of insecticide plus rolling persisted to give a lower density of grubs in the year after treatment. Although rolling induced mortality in grubs from the soil surface to below 5 cm, there was negligible mortality in earthworms.

Effects of whitefringed weevil (Graphognathus leucoloma) and black beetle (Heteronychus arator) populations on pasture species

Abstract Grasses were sown as pure species and in mixtures with white clover (Trifolium repens L.) ‘Grasslands Pitau’ or red clover Trifolium pratense L.) ‘Grasslands Pawera’ for 2 mowing trials. The effects of populations of black beetle (Heteronychus arator F.) and whitefringed weevil (Graphognathus leucoloma (Boheman)) on herbage yield and composition of the pasture were monitored over 3 years. Black beetle populations were at damaging numbers only in the first year of the trial and caused marked changes in pasture composition over summer and autumn in the ryegrass (Lolium perenne L.) ‘Grasslands Nui’ and ryegrass/white clover treatments. The ryegrass component was reduced by 36% in the ryegrass treatment with a 77% increase in weed levels. Black beetle feeding in the ryegrass/white clover treatment reduced ryegrass by 67% and increased the white clover component by 30%. Populations of whitefringed weevil caused reductions of 25%–45% in DM in the second and third years of the trial over summer and autu...

Interaction between Oesophagostomum columbianum and Oesophagostomum venulosum in sheep

Interactions between Oesophagostomum columbianum and Oesophagostomum venulosum were studied by comparing the establishment, development and distribution of each species in single and mixed infections in sheep. The establishment of O. venulosum was reduced by 90 % in sheep previously infected with O. columbianum and by a mean of 50 % in sheep given a simultaneous concurrent infection with O. columbianum. Prior or simultaneous infection with O. venulosum had little or no effect on the establishment of O. columbianum. It is concluded that the increase in incidence of O. venulosum in sheep on the Northern Tablelands of New South Wales has been consequent upon but not the cause of the decline in incidence of O. columbianum. The decline in O. columbianum has probably occurred because of a combination of factors including the failure of infective larvae to overwinter on pasture, the use of efficient anthelmintics and changes in pasture composition.

Superphosphate utilization in clover ley farming. I. Effects on pasture and sheep production

From 1962 to 1966 an experiment was carried out at the Agricultural Research Institute, Wagga Wagga, N.S.W., with dry Merino sheep on an annual clover-grass pasture, in which the stocking rate and the rates of topdressing with superphosphate were varied. In the first year Trifolium subterraneum (subterranean clover) responded to superphosphate, particularly at the lowest stocking rates. In the following 2–3 years there was a change to Hordeum leporinum Link (barley grass) dominance. A greater amount of subterranean clover persisted over the years on the unfertilized plots than on the fertilized plots. Clover burr on these treatments was associated with better liveweight performance by sheep over the dry summer-autumn period. However, after the autumn rains germinating barley grass on the topdressed plots allowed rapid liveweight gains to be made by the sheep on those treatments. Greasy wool production per head, averaged over four shearings, was 4.81, 4.36 and 3.86 kg at 5, 10 and 15 sheep per ha respectively. Superphosphate had no significant effect on wool production. Liveweights decreased as the stocking rate increased. However, at a given stocking rate, the liveweight changes were influenced by changes in pasture composition induced by topdressing with superphosphate, as much as by total available pasture. It appears that in this clover ley farming area topdressing can be omitted in the pasture phase of a wool production system after 700 kg superphosphate ha-I have been applied to the soil.

Investigation of Changes in Pasture Composition by Some Classificatory Methods

Investigation of Changes in Pasture Composition by Some Classificatory Methods

THE INFLUENCE OF CATTLE ON PASTURE COMPOSITION AND SECOND GROWTH CONTROL

The observations, over some years, relate to two steep hill country stations where cultivation could not be undertaken and no topdressing had been done. By reducing sheep and increasing cattle, beneficial changes in pasture composition were achieved. In one case cattle were rotationally grazed; in the other they were set stocked. One property is on the East Coast toward Cape Runaway and is bounded by the sea on one side; the hills rise to about 1,000 ft. The other station is inland toward Raetihi and lies between 1,500 and 2,500 ft; the hills are very steep and valleys very narrow. Climatic conditions at the two places are quite different. Mild and fairly equable conditions prevail on the coastal station and there is only a short period of winter dormancy. Cold winters and a longer period of winter dormancy are characteristic of the inland station. Both places have a fairly well distributed rainfall of over 60 in.; short summer droughts occur.