共查询到20条相似文献,搜索用时 15 毫秒
1.
In order to identify faster-growing non-woody species usable for biomass and paper production, four Tagasastes (Chamaecytisus proliferus) from different origins are tested. All the Tagasaste species (T. Huelva, T. Australia, T. New Zealand and T. La Palma island) show a good soil and climatic adaptation to Southwest Spain. The studied Tagasaste provenances shows biomass productivity ranges from 1.0 t ha(-1)yr(-1) to 3.4 th a(-1)yr(-1) (o.d.b.) and 25.3 t ha(-1)yr(-1) to 49.4 t ha(-1)yr(-1) under Mediterranean conditions for first and second year sprouts, respectively. The quantity of solubles and extractives shows similar values when compared with wood materials. A relatively lower lignin content in Tagasaste (from 13.7% to 17.1%) species has been found with respect to other vegetal species. The alpha-celullose contents (43.6-45.3%) were in the range of the normal values expected for the other non-wood raw materials. The study confirms the feasibility of the organocell yield pulping process to Tagasaste provenances. Organocell processes provide an efficient delignification (kappa index from 7.2 to 10.9 and pulp yield from 43.6% to 54.1%). The best results are obtained for the physical properties of paper sheets for Tagasaste from Australia in the second year, with values of tensile index of 16.0 kNm/kg, burst index of 1.12 MPa m2/kg and tear index of 0.55 Nm2/kg. 相似文献
2.
This study develops cost, energy input and carbon emissions for a number of switchgrass supply options. The Integrated Biomass Supply Analysis and Logistics (IBSAL) model developed at Oak Ridge National Laboratory is used to evaluate the delivery systems. Three biomass collection systems: baling, loafing and ensiling are evaluated. The number and operational performance of equipment are specified to complete collection operations within 120 days of harvest after August 1. Bales are stacked and tarped on the farm side. The transport of biomass from the farm side to a biorefinery takes place over a full year cycle, i.e. 365 days. Supply quantities range from 454 to 4540 dry tonnes/day (500-5000 dry tons/day). Delivered costs to a biorefinery with capacity of 1814 dry tonnes/day (2000 dry tons/day) are: 44-47 dollars/dry tonne for delivered bales (round and square); 37 dollars/dry tonne for delivered loafs (size 2.4 m x 3.6 m x 6 m); 40 dollars/dry tonne for chopped biomass; and 48 dollars/dry tonne for ensiled chops. These costs do not include any payment to the farmers or switchgrass farming cost. Based on the data from literature, the switchgrass farming cost can range from 30 to 36 dollars/dry tonne. These costs would be additional to the switchgrass collection and transportation cost. Switchgrass collection is generally less expensive than collection of straw or corn stover because of the assumed high yield of 11 dry tonnes/ha and a denser biomass. Energy consumption for delivery systems at this capacity ranges from 4.8% to 6.3% of the energy content of switchgrass. Additional 1% of the energy content of switchgrass is consumed in its farming. At 1814 dry tonnes/day (2000 dry tons/day) capacity, greenhouse gas emissions ranges from 75 to 100 kg of CO2/dry tonne of switchgrass delivered. 相似文献
3.
Zalucki MP Shabbir A Silva R Adamson D Shu-Sheng L Furlong MJ 《Journal of economic entomology》2012,105(4):1115-1129
Since 1993, the annual worldwide cost of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), control has been routinely quoted to be US$1 billion. This estimate requires updating and incorporation of yield losses to reflect current total costs of the pest to the world economy. We present an analysis that estimates what the present costs are likely to be based on a set of necessary, but reasoned, assumptions. We use an existing climate driven model for diamondback moth distribution and abundance, the Food and Agriculture Organization country Brassica crop production data and various management scenarios to bracket the cost estimates. The "length of the string" is somewhere between US$1.3 billion and US$2.3 billion based on management costs. However, if residual pest damage is included then the cost estimates will be even higher; a conservative estimate of 5% diamondback moth-induced yield loss to all crops adds another US$2.7 billion to the total costs associated with the pest. A conservative estimate of total costs associated with diamondback moth management is thus US$4 billion-US$5 billion. The lower bound represents rational decision making by pest managers based on diamondback moth abundance driven by climate only. The upper estimate is due to the more normal practice of weekly insecticide application to vegetable crops and the assumption that canola (Brassica napus L.) is treated with insecticide at least once during the crop cycle. Readers can decide for themselves what the real cost is likely to be because we provide country data for further interpretation. Our analysis suggests that greater efforts at implementation of even basic integrated pest management would reduce insecticide inputs considerably, reducing negative environmental impacts and saving many hundreds of millions of dollars annually. 相似文献
4.
Elisa Bayraktarov Phoebe J. Stewart‐Sinclair Shantala Brisbane Lisa Bostrm‐Einarsson Megan I. Saunders Catherine E. Lovelock Hugh P. Possingham Peter J. Mumby Kerrie A. Wilson 《Restoration Ecology》2019,27(5):981-991
Coral reef restoration is an increasingly important part of tropical marine conservation. Information about what motivates coral reef restoration as well as its success and cost is not well understood but is needed to inform restoration decisions. We systematically review and synthesize data from mostly scientific studies published in peer‐reviewed and gray literature on the motivations for coral reef restoration, the variables measured, outcomes reported, the cost per hectare of the restoration project, the survival of restored corals, the duration of the project, and its overall spatial extent depending on the restoration technique employed. The main motivation to restore coral reefs for the projects assessed was to further our ecological knowledge and improve restoration techniques, with coral growth, productivity, and survival being the main variables measured. The median project cost was 400,000 US$/ha (2010 US$), ranging from 6,000 US$/ha for the nursery phase of coral gardening to 4,000,000 US$/ha for substrate addition to build an artificial reef. Restoration projects were mostly of short duration (1–2 years) and over small spatial extents (0.01 ha or 108 m2). Median reported survival of restored corals was 60.9%. Future research to survey practitioners who do not publish their discoveries would complement this work. Our findings and database provide critical data to inform future research in coral reef restoration. 相似文献
5.
Josef H. Reichholf 《Studies on Neotropical Fauna and Environment》2013,48(4):251-255
Airborne input of minerals essential for plant growth is significantly more important for the Amazonian rain forest than elsewhere. Annual rates have been calculated to an average of 26.9 kg/ha/yr for phosphate phosphorus and 12.6 kg/ha/yr for potassium. Other nutrients show a similar amount. If these values are representative for Amazonia as a whole, the total amount of nutrient influx via the air (dry input and precipitation) attains a magnitude, which may be well above the level for assuming a local South American source of origin. Phosphate and potassium alone give an average of 15 to 25 million tons per year. It is concluded, therefore, that dust from the Sahara carried by the trade winds provides the bulk of this mineral input, thus influencing the stability and productivity of the Amazonian rain forest. If this conclusion holds true, the pleistocene forest dynamics in Amazonia should have been influenced not only by changes in the amount of rain fall, but also by the transatlantic transport of nutrients. 相似文献
6.
Mario A. Torres-Acosta Viviana Clavijo Christopher Vaglio Andrés F. González-Barrios Martha J. Vives-Flórez Marco Rito-Palomares 《Biotechnology progress》2019,35(5):e2852
Poultry products are one of the major transmission media of Salmonella enteritidis to humans. A promising alternative to reduce the load of Salmonella in poultry are bacteriophages. Elsewhere, a mixture of six bacteriophages has been used successfully, but large-scale production would be necessary to supply potential poultry market and costs analyses have not been calculated yet. For this, a powerful tool to predict production costs is bioprocess modeling coupled with economic analyses. This work aims to model the scaled-up production of a six bacteriophages mixture based on a laboratory/pilot-scale production using Biosolve Process. For the model construction, a combination of experimental and reported data was applied, in which different production alternatives and the range of 1–100% of the Colombian poultry market (at broiler's farm and slaughterhouse) were analyzed. Results indicate that the best cost-effective process configuration/scale is to use one bioreactor (156 L) for the six bacteriophages, then a 0.45 μm filtration for removal of biomass, and a 0.22 μm filtration for sterility; this to supply the 35% of the market size for broiler farms (equivalent to 210 million chickens). This configuration gives a production cost per chicken of US$ 0.02. Additionally, a sensitivity analysis and a theoretical contrast for understanding the impact that titer and recovery have on production scale determined that titer affects the most the cost and requires optimization. The present works serves as a first, and required, approach for the development of phage therapy products that are alternatives to present-day pathogens control strategies. 相似文献
7.
《Animal : an international journal of animal bioscience》2016,10(3):490-499
The aim of this study was to analyze the economic viability of producing dairy goat kids fed liquid diets in alternative of goat milk and slaughtered at two different ages. Forty-eight male newborn Saanen and Alpine kids were selected and allocated to four groups using a completely randomized factorial design: goat milk (GM), cow milk (CM), commercial milk replacer (CMR) and fermented cow colostrum (FC). Each group was then divided into two groups: slaughter at 60 and 90 days of age. The animals received Tifton hay and concentrate ad libitum. The values of total costs of liquid and solid feed plus labor, income and average gross margin were calculated. The data were then analyzed using the Monte Carlo techniques with the @Risk 5.5 software, with 1000 iterations of the variables being studied through the model. The kids fed GM and CMR generated negative profitability values when slaughtered at 60 days (US$ −16.4 and US$ −2.17, respectively) and also at 90 days (US$ −30.8 and US$ −0.18, respectively). The risk analysis showed that there is a 98% probability that profitability would be negative when GM is used. In this regard, CM and FC presented low risk when the kids were slaughtered at 60 days (8.5% and 21.2%, respectively) and an even lower risk when animals were slaughtered at 90 days (5.2% and 3.8%, respectively). The kids fed CM and slaughtered at 90 days presented the highest average gross income (US$ 67.88) and also average gross margin (US$ 18.43/animal). For the 60-day rearing regime to be economically viable, the CMR cost should not exceed 11.47% of the animal-selling price. This implies that the replacer cannot cost more than US$ 0.39 and 0.43/kg for the 60- and 90-day feeding regimes, respectively. The sensitivity analysis showed that the variables with the greatest impact on the final model’s results were animal selling price, liquid diet cost, final weight at slaughter and labor. In conclusion, the production of male dairy goat kids can be economically viable when the kids diet consists mainly of either cow milk or fermented colostrum, especially when kids are slaughtered at 90 days of age. 相似文献
8.
红壤丘陵区粮食生产的生态成本 总被引:2,自引:0,他引:2
人类的生产活动必然对资源与环境造成影响,以红壤丘陵区的湖南省祁阳县为研究对象,应用经济学和生态学方法,对粮食生产中的生态成本进行了研究。结果表明:2008年该区粮食生产生态损失总价值相当于当年农业总产值的4.85%;早、中、晚稻生态成本已分别达到3.18、2.44、3.02元/kg,而出售单价分别为1.76、1.90、1.84元/kg,高成本低收益的情况对该区域的可持续发展产生着不利影响;在当前生产力水平条件下,适度提高化肥、农药、农业机械、农膜、劳动力的投入,提高水稻产量,扩大家庭种植规模,可降低生产单位水稻的生态成本。 相似文献
9.
Leaf-cutting ants are frequently characterized as the major herbivores in the Neotropics, but quantitative data to back up this assumption are scarce. In this study, the consumption and herbivory rates for the entire leaf-cutting ant ( Atta colombica , Formicidae) population in an old secondary forest on Barro Colorado Island (BCI) in Panama were determined over 15 mo (on average 49 colonies). The number of harvested leaf fragments was calculated from monthly refuse deposition rates of the colonies and the regression between refuse deposition and harvesting rates. The inclusion of fragment characteristics (proportion of leaf fragments in the harvest, average fragment weight, and area) allowed us to calculate consumption and herbivory rates at colony, population, and ecosystem levels. The A. colombica population harvested 13.2 tons of biomass/yr and 13.1 ha of leaf area/yr, and deposited 9.4 tons of refuse material/yr. Rates varied considerably among colonies. At the ecosystem level, i.e. , per forest area, herbivory rates were 132 kg biomass/ha/yr and 1310 m2 foliage/ha/yr. For the area on BCI where A. colombica occurs (100 ha), this is equivalent to 2.1 percent of the foliage area in the forest or 1.7 percent of the annual leaf-area production. This value is considerably lower than previously published estimates of leaf-cutting ant herbivory rates in tropical forests. 相似文献
10.
Biotechnological production of itaconic acid and its biosynthesis in <Emphasis Type="Italic">Aspergillus terreus</Emphasis> 总被引:1,自引:0,他引:1
Mitsuyasu Okabe Dwiarti Lies Shin Kanamasa Enoch Y. Park 《Applied microbiology and biotechnology》2009,84(4):597-606
More than 80,000 tons of itaconic acid (IA) is produced worldwide each year and is sold at a price of around US$ 2/kg. The
IA production yield from sugar is higher than 80 g/l. The widespread use of IA in synthetic resins, synthetic fibers, plastics,
rubbers, surfactants, and oil additives has resulted in an increased demand for this product. However, at present, the IA
production capacity exceeds the demand because this product has a restricted range of applications. Studies have been actively
conducted in different biomedical fields—dental, ophthalmic, and drug delivery—to extend the range of applications of IA.
Recently, many researchers have attempted to replace the carbon source used for microbial production of IA with cheaper alternative
substrates. However, there is still a need for new biotechnology innovations that would help to reduce the production costs,
such as innovative process development and strain improvement to allow the use of a low-quality carbon source. In this short
review, we discuss the following aspects of IA production: strain improvement, process development, identification of the
key enzyme cis-aconitic acid decarboxylase (CAD) in the IA metabolic pathway, metabolic importance of CAD, and new applications of IA. 相似文献
11.
Itaconic acid (IA) is an unsaturated dicarbonic organic acid. It can easily be incorporated into polymers and may serve as a substitute for petrochemical-based acrylic or methacrylic acid. It is used at 1-5% as a co-monomer in resins and also in the manufacture of synthetic fibres, in coatings, adhesives, thickeners and binders. The favoured production process is fermentation of carbohydrates by fungi, with a current market volume of about 15,000 t/a. Due to the high price of about US$ 4/kg, the use of IA is restricted. At present, the production rates do not exceed 1 g l(-1) h(-1), accompanied by product concentrations of about 80 g l(-1). New biotechnology approaches, such as immobilisation techniques, screening programmes and genetic engineering, could lead to higher productivity. Also, the use of alternative substrates may reduce costs and thus open the market for new and increased applications. 相似文献
12.
ABE production from corn: a recent economic evaluation 总被引:2,自引:0,他引:2
This article details an economic assessment of butanol production from corn using the newly developed hyper-butanol-producing
strain of Clostridium beijerinckii BA101. Butanol is produced in batch reactors and recovered by distillation. For a plant with 153,000 metric tons of acetone,
butanol, and ethanol (ABE) production capacity, the production equipment cost and total working capital cost is US$33.47×106 and US$110.46×106, respectively. Based on a corn price (C
p) of US$79.23 ton−1 (US$2.01 bushel−1), an ABE yield of 0.42 (g ABE/g glucose) butanol price is projected to be US$0.34 kg−1. An improved yield of 0.50 will reduce this price to US$0.29 kg−1. Assumptions, such as by-product credit for gases and complete conversion of corn steep liquor (CSL) to fermentation by-products,
have been taken into consideration. An increased price of corn to US$197.10 ton−1 would result in a butanol price of US$0.47 kg−1. A grass-rooted plant would result in a butanol price of US$0.73 kg−1 (C
p US$79.23 ton−1). In a worst case scenario, the price of butanol would increase to US$1.07 kg−1 (C
p 197.10 ton−1 for a grass-rooted plant and assuming no credit for gases). This is based on the assumption that corn price would not increase
to more than US$197.10 ton−1.
Journal of Industrial Microbiology & Biotechnology (2001) 27, 292–297.
Received 12 September 2000/ Accepted in revised form 12 January 2001 相似文献
13.
Naeema A. Akbar Abdullah M. Assiri Omima I. Shabouni Osama M. Alwafi Rajaa Al-Raddadi Mohamad H. Alzahrani Esam I. Azhar Ashraf Amir Abdullah M. Aljiffri Abdulhakeem O. Althaqafi 《PLoS neglected tropical diseases》2020,14(11)
Rapid urbanization, global trade, and the exceptionally great numbers of worldwide visitors during Hajj and Umrah have all placed the Kingdom of Saudi Arabia at a significant risk of introducing several vector-borne tropical diseases, such as dengue fever virus (DENV) infection. In this study we estimated DENV infection cost of illness (COI) in Saudi Arabia in the period 2013–2017, by processing national data including all declared cases recorded in referral centers in the western region, being the endemic region of the country. Using a statistically validated predictive model that was built on a representative sample of 717 laboratory-confirmed cases of DENV infection, direct costs, due to care-related expenditures, were estimated by applying the predictive equation to national data. However, indirect costs, which are due to productivity loss, were estimated using the human capital model based on gross domestic product adjusted for invalidity duration. Further, under-reporting was adjusted by using an expansion factor EF = 3. We observed highest estimated costs in 2016 with over US$168.5 Million total costs, including direct (US$29.0 Million) and indirect (US$139.5 Million) costs, for a total 4415 confirmed cases. The total DENV COI for the five years was estimated as US$551.0 Million for a total 15,369 patients (59.7%) out of 25,745 declared cases, resulting in an average cost of US$11 947.6 by patient. Depending on the year, productivity years loss costs accounted for 63.3% to 83.8% of the estimated total costs. Dengue has a substantial local economic burden that costs US$110.2 Million per year, stressing the urgent need for an effective national prevention strategy to perform considerable cost-savings besides reducing morbidity. 相似文献
14.
José M. Aguilar‐Yáñez Jorge Benavides Marco Rito‐Palomares 《Biotechnology progress》2016,32(6):1472-1479
β‐Phycoerythrin is a color protein with several applications, from food coloring to molecular labeling. Depending on the application, different purity is required, affecting production cost and price. Different production and purification strategies for B‐phycoerythrin have been developed, the most studied are based on the production using Porphyridium cruentum and purified using chromatographic techniques or aqueous two‐phase systems. The use of the latter can result in a less expensive and intensive recovery of the protein, but there is lack of a proper economic analysis to study the effect of using aqueous two‐phase systems in a scaled‐up process. This study analyzed the production of B‐Phycoerythrin using real data obtained during the scale‐up of a bioprocess using specialized software (BioSolve, Biopharm Services, UK). First, a sensitivity analysis was performed to identify critical parameters for the production cost, then a Monte Carlo analysis to emulate real processes by adding uncertainty to the identified parameters. Next, the bioprocess was analyzed to determine its financial attractiveness and possible optimization strategies were tested and discussed. Results show that aqueous two‐phase systems retain their advantages of low cost and intensive recovery (54.56%); the costs of production per gram calculated (before titer optimization: US$15,709 and after optimization: US$2,374) allowed to obtain profit (in the range of US$millions in a 10‐year period) for a potential company taking this production method by comparing the production cost against commercial prices. The bioprocess analyzed is a promising and profitable method for the generation of a highly purified B‐phycoerythrin. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1472–1479, 2016 相似文献
15.
We describe Conoco's closed-loop approach to reducing undesirable emissions through vapor recovery at some of its natural gas production facilities near Corpus Christi, Texas. In response to the U.S. Clean Air Act Amendments of 1990 (CAAA), Conoco developed a technological solution that routed emissions from the facilities to fuel scrubbers and condensers to capture usable product and hazardous air pollutants. Usable product was sold. Nonsalable emissions were routed to on-site equipment as fuel. The new technology was designed without power needs because electricity was not available. In completing these modifications, a closed system (approaching zero emissions) for these facilities was achieved. This innovation saved and earned money for the firm and allowed Conoco to retain its autonomy in these operations.
The solution was so effective that the air quality permits under the CAAA were not required for these production facilities, for a total out-of-pocket cost of 560,000 (plus earned revenue). The firm saved 2,535,000 in initial and 1,359,000 in annual permit costs and fees. The technology recovered 210,000/yr worth of vent gas as on-site fuel and 3,633 barrels/yr of saleable condensate valued at 58,128/ yr. At the same time, it reduced its division environmental impact by 884 tons/year of nitrogen oxides, 2,366 tons/yr of volatile organic compounds, and 495 tons/yr of other hazardous air pollutants. Payout of this 560,000 investment was less than 2 years. 相似文献
The solution was so effective that the air quality permits under the CAAA were not required for these production facilities, for a total out-of-pocket cost of 560,000 (plus earned revenue). The firm saved 2,535,000 in initial and 1,359,000 in annual permit costs and fees. The technology recovered 210,000/yr worth of vent gas as on-site fuel and 3,633 barrels/yr of saleable condensate valued at 58,128/ yr. At the same time, it reduced its division environmental impact by 884 tons/year of nitrogen oxides, 2,366 tons/yr of volatile organic compounds, and 495 tons/yr of other hazardous air pollutants. Payout of this 560,000 investment was less than 2 years. 相似文献
16.
BACKGROUND: The health and economic impact of mental and behavioural disorders (MBD) is wide-ranging, long-lasting and large. Unfortunately, unlike in developed countries where studies on the economic burden of MBD exist, there is a dearth of such studies in the African Region of the World Health Organization. Yet, a great need for such information exists for use in sensitizing policy-makers in governments and civil society about the magnitude and complexity of the economic burden of MBD. The purpose of this study was to answer the following question: From the societal perspective (specifically the families and the Ministry of Health), what is the total cost of MBD patients admitted to various public hospitals in Kenya? METHODS: Drawing information from various secondary sources, this study used standard cost-of-illness methods to estimate: (a) the direct costs, i.e. those borne by the health care system and the family in directly addressing the problem of MBD; and (b) the indirect costs, i.e. loss of productivity caused by MBD, which is borne by the individual, the family or the employer. The study was based on Kenyan public hospitals, either dedicated to care of MBD patients or with a MBD ward. RESULTS: The study revealed that: (i) in the financial year 1998/99, the Kenyan economy lost approximately US$13,350,840 due to institutionalized MBD patients; (ii) the total economic cost of MBD per admission was US$2,351; (iii) the unit cost of operating and organizing psychiatric services per admission was US$1,848; (iv) the out-of-pocket expenses borne by patients and their families per admission was US$51; and (v) the productivity loss per admission was US$453. CONCLUSIONS: There is an urgent need for research in all African countries to determine: national-level epidemiological burden of MBD, measured in terms of the prevalence, incidence, mortality, and, probably, the disability-adjusted life-years lost; and the economic burden of MBD, broken down by different productive and social sectors and occupations of patients and relatives. 相似文献
17.
Benefits of rebuilding global marine fisheries outweigh costs 总被引:1,自引:0,他引:1
UR Sumaila W Cheung A Dyck K Gueye L Huang V Lam D Pauly T Srinivasan W Swartz R Watson D Zeller 《PloS one》2012,7(7):e40542
Global marine fisheries are currently underperforming, largely due to overfishing. An analysis of global databases finds that resource rent net of subsidies from rebuilt world fisheries could increase from the current negative US$13 billion to positive US$54 billion per year, resulting in a net gain of US$600 to US$1,400 billion in present value over fifty years after rebuilding. To realize this gain, governments need to implement a rebuilding program at a cost of about US$203 (US$130-US$292) billion in present value. We estimate that it would take just 12 years after rebuilding begins for the benefits to surpass the cost. Even without accounting for the potential boost to recreational fisheries, and ignoring ancillary and non-market values that would likely increase, the potential benefits of rebuilding global fisheries far outweigh the costs. 相似文献
18.
A. J. Cherry N. E. Jenkins G. Heviefo R. Bateman C. J. Lomer 《Biocontrol Science and Technology》1999,9(1):35-51
Aerial conidia of Metarhizium anisopliae (flavoviride) var. acridum strain IMI 330189 used for the inundative biological control of grasshoppers and locusts in sub-Saharan Africa are produced in a purpose-built facility at the International Institute for Tropical Agriculture in Benin using a standard, two-stage mass-production system. The yields average 31.1 g of dry conidia powder/kg of rice substrate, the production capacity is 300-350 kg of conidia/year and the production costs are estimated at US$21/100 g (the recommended dose for 1 ha). The production process parameters vary within narrow limits established during optimization, but the yield is characterized by a high level of variation over time. The incubation period and temperature are identified as key factors, although they account for less than 40% of the yield variation. The variation in conidial viability and contamination are correlated with several parameters, but none can adequately explain this variation. The handling time, a principal limiting factor, could be reduced by increasing the substrate quantity/unit of production. An awareness of these factors presents the opportunity to fine tune production, although the options for increasing or improving production efficiency are limited within the constraints of the system. 相似文献
19.
Mass- and density-dependent reproductive success and reproductive costs in a capital breeder 总被引:18,自引:0,他引:18
For capital breeders, mass may affect reproductive potential. Reproductive expenditure may reduce future reproductive potential, particularly when resources are scarce. To test the hypothesis that reproductive success and the costs of reproduction vary according to mass and population density, we analyzed 25 yr of data on bighorn ewes (Ovis canadensis). The number of adult females was first limited by yearly removals, then allowed to triple. We found no survival costs of reproduction for ewes aged 4-7 yr. For ewes aged 8-14 yr, survival was density dependent for barren ewes but not for ewes that weaned lambs. Failure to lamb was rare and negatively correlated with fertility the following year. At low population density, lactation had a negative effect on mass gain but had a limited reproductive cost. At high density, heavy ewes had higher reproductive success than light ewes, and the reproductive cost and somatic costs of reproduction increased. The cost of reproduction was greater for light than for heavy ewes. Survival of weaned lambs to 1 yr was affected by population density but not by maternal mass or previous reproductive success. In large mammals, manipulations of reproductive effort are problematic, but long-term monitoring of individual mass and reproductive success under varying conditions of resource availability can provide insights into the evolution of life histories. 相似文献
20.
Bryony A. Jones Karl M. Rich Jeffrey C. Mariner John Anderson Martyn Jeggo Sam Thevasagayam Yi Cai Andrew R. Peters Peter Roeder 《PloS one》2016,11(2)
Peste des petits ruminants (PPR) is an important cause of mortality and production loss among sheep and goats in the developing world. Despite control efforts in a number of countries, it has continued to spread across Africa and Asia, placing an increasing burden on the livelihoods of livestock keepers and on veterinary resources in affected countries. Given the similarities between PPR and rinderpest, and the lessons learned from the successful global eradication of rinderpest, the eradication of PPR seems appealing, both eliminating an important disease and improving the livelihoods of the poor in developing countries. We conducted a benefit-cost analysis to examine the economic returns from a proposed programme for the global eradication of PPR. Based on our knowledge and experience, we developed the eradication strategy and estimated its costs. The benefits of the programme were determined from (i) the averted mortality costs, based on an analysis of the literature, (ii) the downstream impact of reduced mortality using a social accounting matrix, and (iii) the avoided control costs based on current levels of vaccination. The results of the benefit-cost analysis suggest strong economic returns from PPR eradication. Based on a 15-year programme with total discounted costs of US$2.26 billion, we estimate discounted benefits of US$76.5 billion, yielding a net benefit of US$74.2 billion. This suggests a benefit cost ratio of 33.8, and an internal rate of return (IRR) of 199%. As PPR mortality rates are highly variable in different populations, we conducted a sensitivity analysis based on lower and higher mortality scenarios. All the scenarios examined indicate that investment in PPR eradication would be highly beneficial economically. Furthermore, removing one of the major constraints to small ruminant production would be of considerable benefit to many of the most vulnerable communities in Africa and Asia. 相似文献