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1.
Comparative life cycle environmental impacts of three beef production strategies in the Upper Midwestern United States 总被引：1，自引：0，他引：1
We used ISO-compliant life cycle assessment (LCA) to compare the cumulative energy use, ecological footprint, greenhouse gas emissions and eutrophying emissions associated with models of three beef production strategies as currently practiced in the Upper Midwestern United States. Specifically we examined systems where calves were either: weaned directly to feedlots; weaned to out-of-state wheat pastures (backgrounded) then finished in feedlots; or finished wholly on managed pasture and hay. Impacts per live-weight kg of beef produced were highest for pasture-finished beef for all impact categories and lowest for feedlot-finished beef, assuming equilibrium conditions in soil organic carbon fluxes across systems. A sensitivity analysis indicated the possibility of substantial reductions in net greenhouse gas emissions for pasture systems under conditions of positive soil organic carbon sequestration potential. Forage utilization rates were also found to have a modest influence on impact levels in pasture-based beef production. Three measures of resource use efficiency were applied and indicated that beef production, whether feedlot or pasture-based, generates lower edible resource returns on material/energy investment relative to other food production strategies. 相似文献
2.
《Agricultural Systems》2005,83(1):27-48
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. 相似文献
3.
Martin Upton 《Agricultural Systems》1985,17(2):65-83
Dwarf goats and sheep are ubiquitous in the humid zone of West Africa, although only as a supplement to cash and food crop production. This paper presents estimates of the returns obtained from these small ruminants under traditional production systems. Returns are, on average, high, but variable, especially in view of disease risks. Apart from disease control measures to reduce mortality, improved nutrition is needed for intensifying production. At current levels of management neither pasture production nor housing and hand-feeding are likely to yield increased returns. Alley farming, a system of intercropping with shrub species and the feeding of shrub trimmings to small ruminants, seems a promising alternative. 相似文献
4.
M.L. Curll 《Agricultural Systems》1978,3(3):195-204
A model of a steer beef production system, developed for a Mediterranean environment in Argentina, was evaluated for a similar environment in Australia. After testing against experimental data, the model was used to examine the effects of a range of pasture growth responses to a current application of superphosphate in an average and a poor season, and for different combinations of stocking rates, beef prices and dates of sale.Gross margins were small at low stocking rate, irrespective of the level of pasture response to fertiliser. In an average season, higher stocking rates were profitable, particularly if prices were high and large responses possible. In a poor season, however, these same stocking rates gave negative gross margins although large responses did reduce the size of the loss. The adverse effects of a poor season were least at lower stocking rates or if steers were sold earlier at the end of spring rather than in late summer.It is suggested that, where data on the growth response of pasture to fertiliser in a given farm situation are provided, this simple model can provide an early assessment of subsequent fertiliser strategy in that situation. 相似文献
5.
《Agricultural Systems》2002,72(2):133-148
The economic productivity of native pasture systems on the New South Wales tablelands has undergone significant change over the past 40 years. The continued modification by landholders of native pastures with fertilisers and introduced species has been an important contributing factor. Using the economic methods of productivity analysis and linear programming, this paper investigates the extent of native pasture productivity change and the relative economic returns to four general native pasture systems. The results quantify declining productivity trends in native pastures overall, but also establish that the native pasture type systems based on high-quality indigenous species can yield good economic returns under sound management. Some implications of these results for research into and the promotion of native pasture systems are discussed. 相似文献
6.
This paper combines an agricultural production decision support tool, GrassGro, with economic risk efficiency theory to examine several cattle feeding options that include various grazing systems for three climatic environments in Saskatchewan, Canada. Historical weather data were used to simulate a distribution of forage and cattle production data for each of several grazing systems during a 21-year period, 1978–1998. Price variability was included by varying year 2000 prices using historical price margin changes between the buying and selling weights of cattle. The risk efficiency analysis was completed using the Mean Standard Deviation (MSD) framework, and stochastic dominance principles.
Results of the study suggested that feeding systems, which included grazing, were economically competitive with traditional feedlot feeding systems and grain farming. Finishing cattle on pasture with the addition of a barley supplement was an attractive option, especially when high pasture productivity can be achieved. In all locations, more intense systems that included pasture fertilization and provision of an energy supplement, improved production and risk efficiency. Although the average net returns of all these feeding simulations were negative, the returns of traditional grain crops were even more negative. It is these negative returns in grain operations that lead to the incentive for producers to diversify into cattle production. Despite the negative net returns, the cash flow (range −$15.59 to $407.54 ha−1) was mostly positive in all three locations. 相似文献
7.
《Agricultural Systems》2005,83(3):277-295
In Central Brazil, the long-term sustainability of beef cattle systems is under threat over vast tracts of farming areas, as more than half of the 50 million hectares of sown pastures are suffering from degradation. Overgrazing practised to maintain high stocking rates is regarded as one of the main causes. High stocking rates are deliberate and crucial decisions taken by the farmers, which appear paradoxical, even irrational given the state of knowledge regarding the consequences of overgrazing. The phenomenon however appears inextricably linked with the objectives that farmers hold. In this research those objectives were elicited first and from their ranking two, `asset value of cattle (representing cattle ownership)' and `present value of economic returns', were chosen to develop an original bi-criteria Compromise Programming model to test various hypotheses postulated to explain the overgrazing behaviour. As part of the model a pasture productivity index is derived to estimate the pasture recovery cost. Different scenarios based on farmers' attitudes towards overgrazing, pasture costs and capital availability were analysed. The results of the model runs show that benefits from holding more cattle can outweigh the increased pasture recovery and maintenance costs. This result undermines the hypothesis that farmers practise overgrazing because they are unaware or uncaring about overgrazing costs. An appropriate approach to the problem of pasture degradation requires information on the economics, and its interplay with farmers' objectives, for a wide range of pasture recovery and maintenance methods. Seen within the context of farmers' objectives, some level of overgrazing appears rational. Advocacy of the simple `no overgrazing' rule is an insufficient strategy to maintain the long-term sustainability of the beef production systems in Central Brazil. 相似文献
8.
This paper describes the experiences of the authors with the Texas A&M University model when used to simulate the production of beef cattle in a grazing system. Problems associated with the lack of interaction between pasture and animals, including the monthly time interval, supplementation and an input parameter (weight at maturity), are discussed. 相似文献
9.
《Agricultural Systems》1987,25(4):279-295
A biophysical model GRAZE is used to simulate pasture growth and animal weight gain for steers pastured on Bermudagrass. Economic performance is simulated for a continuously grazed pasture and compared to the performance of nine systems in which a rotational grazing schedule is strictly adhered to. Sensitivity of the performance of each strategy to weather risk is assessed for ten alternative weather scenarios, and each pasture management system is ranked for trade-offs between risk and returns using stochastic dominance ordering. Results indicate that expected net returns are highest with a continuous grazing system, but that risk considerations may influence some producers to select one of the rotational systems. 相似文献
10.
A model of the US beef production system has been utilised to project tradeoffs between minimised cost of feeding and minimised fossil energy use to produce amounts of beef similar to 1976 consumption. Cost minimisation approaches the present actual beef production system, but suggests increases in bull feeding and the use of silage and grass finishing of cattle. Energy minimisation indicated energy savings could exceed the equivalent of 240 million barrels of crude oil/year. If energy costs increased three times the 1979 levels, energy and cost minimised solutions appear equivalent.USDA ‘Choice’ grade has been a cost effective strategy, even without consideration of price differentials for the higher quality beef. However, maintenance of current levels of ‘Choice’ beef production does not appear optimal from an energy efficiency standpoint. The model results for energy minimisation suggest an increase in grass finishing and feeding of large bulls, rather than steers, practices which could further reduce fossil fuel inputs, but would result in less ‘Choice’ quality meat. Each increase in energy efficiency in the beef system (other than simple elimination of waste) may be anticipated to have a cost penalty over current practice, given constant or moderately increasing energy costs.However, if energy prices were to reach three times their present level, the model suggests that national cost minimisation would require more energy efficient production systems, and the production of the higher quality beef grades would increase in relative expense. The beef industry does not, at present, minimise energy input because energy's apparent real cost has been low compared with other inputs. 相似文献
11.
Life cycle assessment of greenhouse gas emissions from beef production in western Canada: A case study 总被引：2，自引：0，他引：2
Karen A. Beauchemin H. Henry Janzen Shannan M. Little Tim A. McAllister Sean M. McGinn 《Agricultural Systems》2010,103(6):371-379
A life cycle assessment (LCA) was conducted to estimate whole-farm greenhouse gas (GHG) emissions from beef production in western Canada. The aim was to determine the relative contributions of the cow-calf and feedlot components to these emissions, and to examine the proportion of whole-farm emissions attributable to enteric methane (CH4). The simulated farm consisted of a beef production operation comprised of 120 cows, four bulls, and their progeny, with the progeny fattened in a feedlot. The farm also included cropland and native prairie pasture for grazing to supply the feed for the animals. The LCA was conducted over 8 years to fully account for the lifetime GHG emissions from the cows, bulls and progeny, as well as the beef marketed from cull cows, cull bulls, and progeny raised for market. The emissions were estimated using Holos, a whole-farm model developed by Agriculture and Agri-Food Canada. Holos is an empirical model, with a yearly time-step, based on the Intergovernmental Panel on Climate Change methodology, modified for Canadian conditions and farm scale. The model considers all significant CH4, N2O, and CO2 emissions and removals on the farm, as well as emissions from manufacture of inputs (fertilizer, herbicides) and off-farm emissions of N2O derived from nitrogen applied on the farm. The LCA estimated the GHG intensity of beef production in this system at 22 kg CO2 equivalent (kg carcass)−1. Enteric CH4 was the largest contributing source of GHG accounting for 63% of total emissions. Nitrous oxide from soil and manure accounted for a further 27% of the total emissions, while CH4 emissions from manure and CO2 energy emissions were minor contributors. Within the beef production cycle, the cow-calf system accounted for about 80% of total GHG emissions and the feedlot system for only 20%. About 84% of enteric CH4 was from the cow-calf herd, mostly from mature cows. It follows that mitigation practices to reduce GHG emissions from beef production should focus on reducing enteric CH4 production from mature beef cows. However, mitigation approaches must also recognize that the cow-calf production system also has many ancillary environmental benefits, allowing use of grazing and forage lands that can preserve soil carbon reserves and provide other ecosystems services. 相似文献
12.
A model for optimal distribution of water in the canal command areas has been developed. Water production functions in the form of polynomial expressions were developed from existing experimental information. Using the production functions, water distribution is indicated in order to obtain maximum returns. It has been shown that higher returns can be obtained from canal command areas by a suitable modification of the existing water release pattern at the outlet. 相似文献
13.
This study used whole-farm management, nutrient budgeting/greenhouse gas (GHG) emissions and feed formulation computer tools to determine the production, environmental and financial implications of intensifying the beef production of typical New Zealand (NZ) sheep and beef farming systems. Two methods of intensification, feeding maize silage (MS) or applying nitrogen (N) fertiliser, were implemented on two farm types differing in the proportions of cultivatable land to hill land (25% vs. 75% hill). In addition, the consequences of intensification by incorporating a beef feedlot (FL) into each of the farm types were also examined.Feeding MS or applying N fertiliser substantially increased the amount of beef produced per ha. Intensifying production was also associated with increased total N leaching and GHG emissions although there were differences between the methods of intensification. Feeding MS resulted in lower environmental impacts than applying N even after taking into account the land to grow the maize for silage. Based on 2007/08 prices, typical NZ sheep and beef farms were making a financial loss and neither method of intensification increased profitability with the exception of small annual applications of N, especially to the 75% hill farm. These small annual additions of N fertiliser (<50 kg N/ha/yr applied in autumn and late winter) resulted in only small increases in annual N leaching (from 11 to 14 kg N/ha) and GHG emissions (from 3280 to 4000 kg CO2 equivalents/ha). Limited N applications were particularly beneficial to 75% hill farms because small increases in winter carrying capacity resulted in relatively large increases in the utilisation of pasture growth during spring and summer than the 25% hill farms. Intensification by incorporating a beef feedlot reduced environmental emissions per kg of beef produced but considerably decreased profitability due to higher capital, depreciation and labour costs. The lower land-use capability farm type (75% hill) was able to intensify beef production to a proportionally greater extent than the higher land-use capability farm (25% hill) because of greater potential to increase pasture utilisation associated with a lower initial farming intensity and inherent constraints in the pattern of pasture supply. 相似文献
14.
《Agricultural Systems》1999,61(2):135-146
In Central Brazil, half the area under sown pasture suffers from the phenomenon of pasture degradation; overgrazing is believed to be the main cause. Farmers' objectives and their links to the practice of overgrazing have been explored to obtain a better understanding of the decisions related to the setting of the stocking rate. A survey of beef cattle farmers was carried out, preceded by an exploratory poll of experts on such production systems. The method of paired comparisons was used for eliciting and analysing farmers' objectives. ‘Intergenerational transfer’ and ‘cattle ownership’ are the most dominant objectives. Because cattle ownership is implicitly included in the assets involved in intergenerational transfer, possessing cattle assumes an outstanding importance in the hierarchy of farmers' objectives. These findings elucidate the paradox of overgrazing and provide a basis for treating the perception on the influence of objectives on the degradation phenomenon from being a conjecture to that of an empirically valid hypothesis. They also suggest the need for incorporating the objective ‘maximise the number of cattle owned’ in the analysis and modelling of stocking rate decisions. 相似文献
15.
16.
《Agricultural Systems》1999,59(2):145-161
Options are explored for sustainable, i.e. non-soil-nitrogen (N) mining, beef production in the humid tropical Atlantic Zone of Costa Rica using a modelling approach. Tools used are linear programming and a technical coefficient generator called PASTOR. Due to the combination of high rainfall, highly permeable soils and high N turnover rates, N losses are high and current natural pastures are calculated to mine soil N reserves with 40–60 kg ha−1 year−1. With current financial returns, there is no economic incentive for farmers to convert soil mining natural pastures to sustainable alternatives, viz. grass–legume mixtures or fertilized improved grasslands. When degradation of natural pastures over time due to soil N mining is considered in the model, it becomes economically attractive to replace these pastures with grass–legume mixtures. Sustainable beef cattle ranching is best realized by integrated intensification that raises total economic returns, i.e. use of grass–legumes or fertilized pastures, high levels of feed supplements and improved herd management techniques. 相似文献
17.
D.H. White P.J. Bowman F.H.W. Morley W.R. McManus S.J. Filan 《Agricultural Systems》1983,10(3):149-189
A simulation model was constructed of a self-replacing flock of Merino ewes grazing a predominantly Wimmera ryegrass and subterranean clover pasture in the Eppalock catchment of northern Victoria, Australia. The model was used to predict the likely physical, biological and economic consequences of changes in stocking rate and date of lambing.Routines for simulating the local climate, together with expected levels of pasture production, were based on available local data. The herbage produced was utilised for animal maintenance, growth, pregnancy, lactation and wool production. Predictions were made of the ovulation and fertilisation rates of the breeding ewes and the subsequent survival of embryos and lambs. Lamb growth rates were determined relative to their predicted intake levels of milk and herbage.The economic consequences of different combinations of ewe stocking rate and date of lambing were evaluated by simulating the cash flow of the property. Financial returns were obtained from the sale of wool, cast-for-age and culled ewes, and wether lambs. 相似文献
18.
《Agricultural Systems》1987,24(2):119-148
A mathematical model of herbage production and utilization on grass and grass-clover swards in the context of an 18-month beef system is described. Using the model the potential costs and benefits of replacing grass by grass-clover mixtures are examined. It is projected that gross margins per hectare will be higher on grass-clover swards receiving little or no fertilizer N than on grass swards receiving 300kg N ha−1. The higher average profits from grass-clover systems must be set against a higher year-to-year variation in the financial returns. To some extent the financial risk associated with the more variable annual profits may be reduced by only allocating a proportion of the forage area to grass-clover and continuing to devote the rest of the area to fertilized grass swards.These conclusions, which are at variance with other studies, are influenced by three key assumptions within the model. First, dry-matter intakes by beef cattle are presumed to be about 10% higher on grass-clover than on grass swards. Secondly, the metabolizable energy value of clover is assumed to be 5% higher than grass. Thirdly, the model projects that the available forage is utilized more efficiently on grass-clover swards, due to the more uniform seasonal pattern of herbage production. If some or all of these assumptions are rejected, the economic advantage moves in favour of grass-based production systems. Since confirmation of these assumptions awaits experimental work, the findings of the model can be seen as little more than informed speculation. 相似文献
19.
介绍了国内外牧草免耕播种机械化技术研究情况,分析了国外一些代表机型的特点,同时介绍了两种典型牧草的栽培技术措施,为国内企业进一步研制开发牧草免耕播种机系列产品提供参考。 相似文献
20.
N.R. Brockington C.A. Gonzalez J.M. Veil R.R. Vera N.M. Teixeira A.G. de Assis 《Agricultural Systems》1983,12(1):37-60
This paper reports on the development and use of a bioeconomic model to simulate dairy enterprises in the Zona da Mata of Minas Gerais State in south-east Brasil.In view of the relatively small size of the units, each animal within the herd is accounted for on an individual basis and the main biological events and processes are treated stochastically. Within the limits of given herdranges for genetic potentials, actual rates of performance are estimated from the levels of feeding and other management factors. An energy balance approach is used to assess the contributions of pasture, cut forage and concentrates in the diet.The model has been used to help in identifying priority areas for applied research, to explore various combinations of herd potential and level of feeding, the behaviour of different herd sizes and the potential returns from specific technical innovations. 相似文献