Intensification of New Zealand beef farming systems

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.     

Greenhouse gas emissions from the Canadian beef industry

Commodity-specific estimates of the greenhouse gas (GHG) emissions from Canadian agriculture are required in order to identify the most efficient GHG mitigation measures. In this paper, the methodology from the Intergovernmental Panel on Climate Change (IPCC) for estimating bovine GHG emissions, for census years from 1981 to 2001, was applied to the Canadian beef industry. This analysis, which is based on several adaptations of IPCC methodology already done for the Canadian dairy industry, includes the concept of a beef crop complex, the land base that feeds the beef population, and the use of recommendations for livestock feed rations and fertilizer application rates to down-scale the national area totals of each crop, regardless of the use of that crop, to the feed requirements of the Canada’s beef population. It shows how high energy feeds are reducing enteric methane emissions by displacing high roughage diets. It also calculates an emissions intensity indicator based on the total weight of live beef cattle destined for market. While total GHG from Canadian beef production have increased from 25 to 32 Tg of CO₂ equiv. between 1981 and 2001, this increase was mainly driven by expansion of the Canadian cattle industry. The emission intensity indicator showed that between 1981 and 2001, the Canadian beef industry GHG emissions per kg of live animal weight produced for market decreased from 16.4 to 10.4 kg of CO₂ equiv.     

The impact of various parameters on the carbon footprint of milk production in New Zealand and Sweden

The carbon footprint (CF) of milk production was analysed at the farm gate for two contrasting production systems; an outdoor pasture grazing system in New Zealand (NZ) and a mainly indoor housing system with pronounced use of concentrate feed in Sweden (SE). The method used is based on the conceptual framework of lifecycle assessment (LCA), but only for greenhouse gas (GHG) emissions. National average data were used to model the dairy system in each country. Collection of inventory data and calculations of emissions were harmonised to the greatest extent possible for the two systems. The calculated CF for 1 kg of energy corrected milk (ECM), including related by-products (surplus calves and culled cows), was 1.00 kg carbon dioxide equivalents (CO₂e) for NZ and 1.16 kg CO₂e for SE. Methane from enteric fermentation and nitrous oxide emissions from application of nitrogen (as fertiliser and as excreta dropped directly on the field) were the main contributors to the CF in both countries. The most important parameters to consider when calculating the GHG emissions were dry matter intake (DMI), emission factor (EF) for methane from enteric fermentation, amount of nitrogen applied and EF for direct nitrous oxide emissions from soils. By changing one parameter at a time within ‘reasonable’ limits (i.e. no extreme values assumed), the impact on the total CF was assessed and showed changes of up to 15%. In addition, the uncertainty in CF estimates due to uncertainty in EF for methane from enteric fermentation and nitrous oxide emissions (from soil and due to ammonia volatilisation) were analysed through Monte Carlo simulation. This resulted in an uncertainty distribution corresponding to 0.60-1.52 kg CO₂e kg⁻¹ ECM for NZ and 0.83-1.56 kg CO₂e kg⁻¹ ECM for SE (in the prediction interval 2.5-97.5%). Hence, the variation within the systems based on the main EF is relatively large compared with the difference in CF between the countries.     

A systems approach to quantify greenhouse gas fluxes from pastoral dairy production as affected by management regime

A model was developed to determine what effect management practices would have on the production of the greenhouse gases (GHG) within pastorally based dairy production systems typical of those practiced in Ireland. The model simulates two levels of GHG emissions, firstly the on-farm GHG emissions of methane, nitrous oxide and carbon dioxide for example from the pastorally spreading of slurry and secondly, off-farm GHG emissions associated with both inputs brought onto the farm to maintain productivity (for example emissions arising from manufacture of concentrate feeds and fertiliser) as well as from indirect GHG emissions associated with nitrate leaching and ammonia. The aim of this work was to allow the development of effective GHG mitigation strategies at the farm level capable of reducing GHG emissions per litre of milk.Greenhouse gas emissions were modelled for nine farming systems differing in the level of concentrate supplementation (376, 810 and 1540 kg per cow per lactation) and genotype for milk production as assessed by their pedigree index (<100, 100–200 and 200–300 kg) of milk production. A three-year study to evaluate the influence of cow genetic potential for milk production and concentrate supplementation level on profitability of pasture-based systems of milk production was used to drive the Moorepark Dairy Systems Model (MDSM). Output from this model then described farm size, feed budgets, animal numbers and farm profitability when annual milk quota was set to 468,000 kg of milk year. Relating GHG emissions to annual milk sales revealed that for these pastorally based systems increasing concentrate usage reduced both on-farm and off-farm emissions, but that increasing the genotype of the dairy cow (i.e., the genetic capacity of the animal to produce milk) will increase both on-farm and off-farm GHG emissions. Lowest GHG emissions per kilogram of milk were achieved for an intermediate genotype type cow fed within a high concentrate system whilst the highest emissions were associated with high genotype cows fed within a low concentrate system. Maximum profitability was obtained when either a high concentrate feeding regime was combined with high genotype cows or where low concentrate systems were fed to low genotype cows.Relating farm profitability to GHG emissions allowed the identification of scenarios where changing from one management systems to another would achieve a simultaneous reduction in GHG emissions whilst improving farm profitability. By implementing this approach of assessing management induced change on both GHG emissions arising from the farm together with farm profitability, individual whole farm GHG mitigation strategies could be developed with a high degree of acceptability to the producer.     

Greenhouse gas emissions from the Canadian dairy industry in 2001

In order to demonstrate the impact of an increase in production efficiency on greenhouse gas (GHG) emissions, it is important to estimate the combined methane (CH₄), nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions per unit of production. In this study, we calculated the GHG emissions from the Canadian dairy industry in 2001 as a fraction of the milk production and per dairy animal. Five regions were defined according to the importance of the dairy industry. N₂O and CO₂ emissions are directly linked with areas allocated to the dairy crop complex which includes only the crop areas used to feed dairy cattle. The dairy crop complex was scaled down from sector-wide crop areas using the ratios of dairy diet to national crop production of each crop type. Both fertilizer application and on-farm energy consumption were similarly scaled down from sector-wide estimates to the dairy crop complex in each region. The Intergovernmental Panel on Climate Change (IPCC) methodology, adapted for Canadian conditions, was used to calculate CH₄ and N₂O emissions. Most of the CO₂ emission estimates were derived from a Fossil Fuel for Farm Fieldwork Energy and Emissions model except for the energy used to manufacture fertilizers. Methane was estimated to be the main source of GHG, totalling 5.75 Tg CO₂ eq with around 80% coming from enteric fermentation and 20% coming from manure management. Nitrous oxide emissions were equal to 3.17 Tg CO₂ eq and carbon dioxide emissions were equal to 1.45 Tg. The GHG emissions per animal were 4.55 Mg CO₂ eq. On an intensity basis, average GHG emissions were 1.0 kg CO₂ eq/kg milk. Methane emissions per kg of milk were estimated at 19.3 l CH₄/kg milk which is in agreement with Canadian field measurements.     

Energy consumption, greenhouse gas emissions and economic performance assessments in French Charolais suckler cattle farms: Model-based analysis and forecasts

The environmental and economic performance of five Charolais beef production systems (three specialized beef producer test cases in grassland areas and two mixed crop-livestock test cases with a more intensive production system) were assessed by coupling an economic optimization model (“Opt’INRA”) with a model assessing non-renewable energy (NRE) consumption and greenhouse gas emissions (“PLANETE”). The test cases studied covered a relatively diverse range of raised and sold animals: calf-to-weanling or calf-to-beef systems (animals sold: from 10-month-old weaners to 36-month-old beef steers). In 2006, NRE consumption ranged from 26,440 to 31,863 MJ/ton of live weight produced over 1 year. Fuels and lubricants were the main factors of NRE consumption, followed by fertilizers and farm equipment. Livestock was the main driver of global warming potential. GHG emissions, at 14.3-18.3 tCO₂eq/t LW, were mainly determined by the proportion of cows in the total herd livestock units, according to the farming system deployed, i.e. calf-to-weanling vs. calf-to-beef. Against a background of rising energy costs, farms running mixed crop-livestock systems enjoy greater flexibility to adjust their farming systems than grassland-based farms, enabling them to minimize the drop in income over the timeframe to 2012 (−3%). In this same setting, specialist beef producers face a 15-25% drop in income. In all the scenarios run, system adjustments designed to minimize the drop in income have only a very limited impact on NRE consumption and GHG emissions.     

Quantification of GHG emissions from sucker-beef production in Ireland

A life cycle assessment (LCA) type method was used to quantify greenhouse gases (GHG) emissions from Irish suckler-beef production. The methodology was used as a systems analysis tool to quantify GHG emissions from a typical Irish beef production system and to evaluate a number of alternative management scenarios. The LCA methodology can be used to decide whether a management strategy will reduce GHG emissions or transfer them elsewhere in the emission basket. Scenarios were developed that examined using both beef-bred animals (Charolais, Simmental and Limousin) and dairy-bred animals (Holstein–Fresian). By scaling total GHG emissions relative to a functional unit (FU) of live weight per year (kg CO₂ kg LW yr⁻¹), it was possible to estimate both the emissions and the potential for emissions reduction by adopting alternative management. The typical suckler-beef system was estimated to produce 11.26 kg CO₂ LW yr⁻¹. For beef-bred animals the cow contributed a large amount to the total emissions whereas for dairy-bred beef production the allocation from the cow was much less. In terms of dietary supplementation for GHG emissions reduction, a broad range of supplement combinations were evaluated and showed no major reduction potential compared to, or within, the grass-dominated system.     

Comparative life cycle environmental impacts of three beef production strategies in the Upper Midwestern United States

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.     

Analysis of greenhouse gas emissions from the average Irish milk production system

Actions to moderate the major emission contributors of enteric fermentation, fertiliser and manure management on farms should not simply move the emissions elsewhere in the system, but actually reduce them. Life cycle assessment methodology was used to provide an objective framework for estimating emissions and to evaluate emission management scenarios with respect to kg CO₂ eq emitted per unit of milk produced. An average dairy unit was defined and emissions were compartmentalised to calculate a total emission of 1.50 kg CO₂ eq kg⁻¹ (energy corrected milk) yr⁻¹ and 1.3 kg CO₂ eq kg⁻¹ yr⁻¹ with economic allocation between milk and meat. Of the total emissions, 49% was enteric fermentation, 21% fertiliser, 13% concentrate feed, 11% dung management and 5% electricity and diesel consumption. Scenario testing indicated that more efficient cows with extensive management could reduce emissions by 14–18%, elimination of non-milking animals could reduce emissions by 14–26% and a combination of both could reduce emissions by 28–33%. It was concluded that the evolution of the Irish dairy sector, driven by the Common Agricultural Policy (CAP), should result in reduced GHG emissions.     

Introducing greenhouse gas mitigation as a development objective in rice-based agriculture: I. Generation of technical coefficients

This study presents a modeling tool to assess emission of greenhouse gases (GHG) from the agricultural sector as affected by land-use and residue utilization options. The overall purpose of this tool is twofold: (i) a spreadsheet model for comprehensive compilation of the direct and indirect emissions from land management, residue-burning and fossil fuel consumption through on-farm and off-farm operations and (ii) a decision support tool to explore economically viable mitigation options through detailed cost–benefit analysis of different technological options. We developed TechnoGAS (technical coefficient generator for mitigation technologies of greenhouse gas emissions from agricultural sectors), which integrates analytical and expert knowledge with regional databases on bio-physical, agronomic and socio-economic features to establish input–output relationships (‘Technical Coefficients’) related to GHG emissions in agriculture. The approach includes emissions of methane (CH₄) from rice fields, rice straw burning and cattle; carbon dioxide (CO₂) from fossil fuel and soil organic carbon decline as well as nitrous oxide (N₂O) from soil, rice straw burning and fertilizer use. To illustrate the approach of the spreadsheet model for comprehensive compilation of emissions, we applied TechnoGAS for an entire rice–wheat cropping cycle in the state of Haryana in northern India as a case study. Twenty technologies of rice production, which can be adopted by farmers, are analysed for their operation-specific emissions including their global warming potential (GWP). The technologies differ in terms of water regime, residue management/utilization, soil management and additives, which represent different mitigation options for GHG emissions. With the current farmers’ practice in various districts in Haryana, soil-borne emissions are the major source of GHG contributing 53% of the average GWP (3288 kg CO₂ equivalent ha⁻¹) in rice followed by burning of rice straw (13% of the GWP). Cattle, farm operations, off-farm and inorganic fertilizer contributes 12%, 10%, 10% and 2% of the GWP, respectively. Emissions from wheat are relatively low (1204 kg CO₂ equivalent ha⁻¹) as there is no CH₄ emission and wheat straw is not burnt. Different mitigation technologies show pronounced effects on the GWP of the rice crop and varied between 1715 kg CO₂ equivalent ha⁻¹ with continuous flooding, urea and rice straw used for building materials and 10,020 kg CO₂ equivalent ha⁻¹ with continuous flooding, and application of nutrients through organic manure. Compared to current farmers’ practice, 13 technologies are found to have the potential to reduce the GWP by 8–51%, but they also reduce the net income of farmers. Upscaling of the estimates to the entire state of Haryana shows that the GWP with the current farmers’ practice in rice is 2617 Gg CO₂ equivalent. Modification of water management from continuous flooding to alternate flooding or application of urea alone instead of urea plus FYM will reduce the GWP by 15% and 29%, respectively, while feeding of rice straw to cattle and supplying N through urea will reduce it by 41% compared to the current practice of burning rice straw and use of FYM. The study shows that the TechnoGAS tool can be used for estimating GHG emission from various land-use types and for identifying promising mitigation options. A detailed cost/benefit analysis is supplied by Wassmann and Pathak [Wassmann, R., Pathak, H., this volume. Introducing greenhouse gas mitigation as a development objective in rice-based agriculture: II. Cost–benefit assessment for different technologies, regions and scales.].     

The environmental performance of milk production on a typical Portuguese dairy farm

The activities associated with raw milk production on dairy farms require an effective evaluation of their environmental impact. The present study evaluates the global environmental impacts associated with milk production on dairy farms in Portugal and identifies the processes that have the greatest environmental impact by using life cycle assessment (LCA) methodology. The main factors involved in milk production were included, namely: the dairy farm, maize silage, ryegrass silage, straw, concentrates, diesel and electricity. The results suggest that the major source of air and water emissions in the life cycle of milk is the production of concentrates. The activities carried out on dairy farms were the major source of nitrous oxides (from fuel combustion), ammonia, and methane (from manure management and enteric fermentation). Nevertheless, dairy farm activities, which include manure management, enteric fermentation and diesel consumption, make the greatest contributions to the categories of impact considered, with the exception of the abiotic depletion category, contributing to over 70% of the total global warming potential (1021.3 kg CO₂ eq. per tonne of milk), 84% of the total photochemical oxidation potential (0.2 kg C₂H₄ eq. per tonne of milk), 70% of the total acidification potential (20.4 kg SO₂ eq. per tonne of milk), and 41% of the total eutrophication potential (7.1 kg eq. per tonne of milk). The production of concentrates and maize silage are the major contributors to the abiotic depletion category, accounting for 35% and 28%, respectively, of the overall abiotic depletion potential (1.4 Sb eq. per tonne of milk). Based on this LCA case study, we recommend further work to evaluate some possible opportunities to improve the environmental performance of Portuguese milk production, namely: (i) implementing integrated solutions for manure recovery/treatment (e.g. anaerobic digestion) before its application to the soil as organic fertiliser during maize and ryegrass production; (ii) improving manure nutrient use efficiency in order to decrease the importation of nutrients; (iii) diversifying feeding crops, as the dependence on two annual forage crops is expected to lead to excessive soil mobilisation (and related impacts) and to insignificant carbon dioxide sequestration from the atmosphere; and (iv) changing the concentrate mixtures.     

The contribution of maize cropping in the Midwest USA to global warming: A regional estimate

Agricultural soils emit about 50% of the global flux of N₂O attributable to human influence, mostly in response to nitrogen fertilizer use. Recent evidence that the relationship between N₂O fluxes and N-fertilizer additions to cereal maize are non-linear provides an opportunity to estimate regional N₂O fluxes based on estimates of N application rates rather than as a simple percentage of N inputs as used by the Intergovernmental Panel on Climate Change (IPCC). We combined a simple empirical model of N₂O production with the SOCRATES soil carbon dynamics model to estimate N₂O and other sources of Global Warming Potential (GWP) from cereal maize across 19,000 cropland polygons in the North Central Region (NCR) of the US over the period 1964-2005. Results indicate that the loading of greenhouse gases to the atmosphere from cereal maize production in the NCR was 1.7 Gt CO₂e, with an average 268 t CO₂e produced per tonne of grain. From 1970 until 2005, GHG emissions per unit product declined on average by 2.8 t CO₂e ha⁻¹ annum⁻¹, coinciding with a stabilisation in N application rate and consistent increases in grain yield from the mid-1970’s. Nitrous oxide production from N fertilizer inputs represented 59% of these emissions, soil C decline (0-30 cm) represented 11% of total emissions, with the remaining 30% (517 Mt) from the combustion of fuel associated with farm operations. Of the 126 Mt of N fertilizer applied to cereal maize from 1964 to 2005, we estimate that 2.2 Mt N was emitted as N₂O when using a non-linear response model, equivalent to 1.75% of the applied N.     

Comparative economics of Holstein/Gir F1 dairy female production and conventional beef cattle suckler herds – A simulation study

Three cow–calf production systems were compared using simulation: N (straightbred Nelore), AN (Nelore cows producing Angus by Nelore calves) and HG (Gir cows producing Holstein by Gir calves). All three systems produced their own straightbred replacement females. Male calves were sold at weaning and female calves in excess of those required to keep the herd size constant were sold at one year of age. In the base situation, F₁ HG females were priced at twice as much as the price per kg of the beef male calves, according to present market values. Typical 1000 ha beef cattle farms were simulated for each system, based on Brachiaria brizantha pastures managed according to recommended practices. Herd dynamics were controlled by reproduction and survival. Literature figures on monthly pasture nutrient production, live weights and milk yield were used to estimate nutrient requirements to match stocking rate to nutrient availability in each system. For calving rate set to 0.8 in all three systems, the total numbers of cows for the N, AN and HG systems were, respectively, 803, 795 and 885 and the total live weight sold annually was 129,070, 133,120 and 127,680 kg. The annual economic return on investment was 5.21%, 5.81% and 10.84%, respectively, for the N, AN and HG systems. Reducing the relative price of the HG heifers diminished the economic superiority of this system over N and AN. The difference was zero when the price of HG heifers was reduced to approximately 1.2 times the beef calf price. This also happened when the calving rate of the Gir cows was set to 0.6 keeping N cows at 0.8 or higher.     

Greenhouse gas implications of water reuse in the Upper Pumpanga River Integrated Irrigation System, Philippines

Enhancing water productivity is often recommended as a “soft option” in addressing the problem of increasing water scarcity. However, improving water productivity, particularly through water reuse, incurs additional investment and may result in increased greenhouse gas (GHG) emissions. In this study, we analysed the water productivity and GHG implications of water reuse through pumping groundwater and creek water, and compare this with gravity-fed canal irrigation in the Upper Pampanga River Integrated Irrigation System (UPRIIS) in the Philippines.Water productivity indicators show that water reuse contributes significantly to water productivity. For example, water productivity with respect to gross inflow (WP_gross) with water reuse (0.19 kg grain/m³) is 21% higher than without water reuse (0.15 kg grain/m³). However, there is a tradeoff between increasing water productivity and water reuse as water reuse increases GHG emissions. The estimated GHG emission from water reuse (pumping irrigation) is 1.47 times higher than without water reuse (gravity-fed canal irrigation). Given increasing concerns about climate change and the need to reduce carbon emissions, we recommend that a higher priority be given to water reuse only in areas where water scarcity is a serious issue.     

Farm types for beef production and their economic success in a mountainous province of northern Vietnam

The objective of this study was to compare the management and economic success of beef production by three types of farm in northwestern Vietnam. The potential of household farms to supply beef for the market and their competition with large farms were examined.The fieldwork was done in 2007 on 73 farms consisting of 58 small mixed farms (small farms), 10 medium mixed farms (medium farms) and 5 specialised large-scale beef farms (large farms) in Son La province. The three types of farm differed in ethnicity (Thai, H’mong, and Kinh), remoteness (lowland, highland), production objectives (subsistence, market output), degree of specialization (mixed farm, specialised beef farm) and integration of production (single farmers, cooperative). Data on biological productivity, inputs and outputs, and the social contribution of cattle production were collected by household and key person interviews, participatory rural appraisal tools and cattle body measurements. Economic values were derived by assessment of market or replacement costs. Quantitative data analysis was done with linear models (PROC GLM) in the SAS software (version 9.1).Lowland small farms had higher costs for cattle production than the highland farms (0.8 Mill. VND head⁻¹ year⁻¹ compared with 0.02 Mill. VND head⁻¹ year⁻¹, respectively). The large farms had high production costs, with an average of 2.5-3.6 Mill. VND head⁻¹ year⁻¹. Cattle brought high benefits of non-cash values to the household farms. The total revenue from cattle was in the range 4.5-11.5 Mill. VND head⁻¹ year⁻¹, which depended on the use of non-market functions of cattle on the household farm. The value of net benefit/kg live weight (LW) of lowland small farms with an average of 39,000 VND/kg LW was significantly higher than that of the medium and small farms in the highlands (26,000 VND/kg LW). However, the small farms kept fewer cattle than the medium farms (average of 2-4 cattle/farm compared with 9 cattle/farm, respectively) because of forage and labour shortages and have no option to further develop cattle production. Keeping larger numbers of cattle based on available natural pasture brought high benefit from stock value as farm liquidity to only the medium farms. This was the most promising type of farm for future development of beef production, given its actual success and the availability of underutilised resources. Large-scale farms suffered high economic losses of 0.3-1.4 Mill. VND cattle⁻¹ year⁻¹, due to the lack of professional management, high feed costs and low animal performance, and showed no potential for developing cattle production.     

Long-term stochastic simulation of mountain beef cattle herds under diverse management strategies

A stochastic simulation model was used to assess the effects of diverse management strategies on beef herds under mountain conditions in the Spanish Pyrenees. Animals grazed on different seasonal resources (valley meadows, forest pastures and mountain pastures) and were fed with forages and concentrates during winter. The simulated management strategies were winter calving (WC, weaning at 180 days), autumn calving (AC, weaning at 160 days), 8-month calving (8MC, weaning at 180 days), and two calvings in 3 years, with weaning taking place at either 170 days of age (2C3Y) or at 9 months (2C3Y9 M). Each strategy was tested for two types of production systems: (i) cow-calf farms that market calves just after weaning; and (ii) cow-calf/finishing farms that fatten the animals by means of an intensive feeding system until achieving a suitable weight for slaughter. A herd of 100 cows was simulated over 15 years, but only data obtained after reaching the steady state (year 6) was used in the analysis. The strategies were evaluated by considering reproductive, productive and economic performance. The percentages of pregnant cows at the end of the mating season were highest for 8MC, 2C3Y and 2C3Y9M (between 92% and 94%). The percentage was intermediate for AC (88%) and lowest for WC (78%), which also showed greater variability between years. The two strategies that extensified management (2C3Y, 2C3Y9M) produced, as expected, a lower number of calves weaned per year (59 and 60), whereas this figure was the highest for 8MC (90). Although AC and 8MC resulted in higher productive performances, the increased labour requirements and winter feeding costs resulted in low economic margins for these strategies, which also meant poorer utilization of natural resources. In economic terms, WC was the best strategy for cow-calf/finishing farms, whereas 2C3Y was the worst of the two types of production systems, although it resulted in the most intense utilization of grazing resources. The long lactating period of 2C3Y9M did not affect the reproductive performance of cows, so this strategy yielded the highest economic margin at weaning. The extensification strategies (2C3Y and 2C3Y9M) were less sensitive to changes in the price of feedstuffs. The information obtained from the simulation of the different strategies is useful for evaluating the possible trade-offs between production, economics, use of natural resources and labour requirements.     

Modelling optimal crop sequences using network flows

In recent years there has been an increased focus on sustainable farming systems. This has led to an increase in the use of farm models built to assess the environmental impact from farming. In whole-farm models including crop production it is important to consider the rotation of crops, since this has a major impact on the consequences of the crop production.     

The environmental impacts of the production of concentrated feed: the case of pig feed in Bretagne

Pig production systems often depend to a large extent on concentrated feed imported from outside the farm. This study used the Life Cycle Assessment (LCA) method to assess major environmental impacts associated with the production and on-farm delivery of concentrated feed for pigs. Feed composition was based on average data for Bretagne (France) in 1998 and on published data for wheat-based, maize-based and co-product based feeds. As crop and feed production practices in Bretagne are similar to those in most of western Europe, we conclude that the results of this study apply more largely for western Europe. Depending on feed composition and fertilisation practise for crop-based feed ingredients, the production and delivery of one kg of feed for finishing pigs will produce a eutrophication potential between 3.8 and 9.3 g PO₄-equivalents, a global warming potential between 472 and 792 g CO₂-equivalents, an acidification potential between 3.0 and 6.3 g SO₂-equivalents, a terrestrial ecotoxicity potential between 0.4 and 8.7 g 1,4-dichlorobenzene-equivalents, an energy use between 3.3 and 6.1 MJ, and land use between 1.44 and 2.07 m² year. These impacts are mainly due to the production of crop-based ingredients. The contribution of transport processes was substantial for climate change, acidification and energy use. A feed containing mainly co-products had higher energy use and lower terrestrial ecotoxicity than feeds consisting mainly of non-processed crop-based ingredients. Hypotheses with respect to the fertilisation practices for the feed's main ingredients have a major effect on its impact values. The effect of uncertainty concerning the emissions of N₂O, NH₃, and NO₃ was very large for climate change, and large for acidification and eutrophication. The environmental burdens associated with the production and delivery of pig feed can be decreased by: optimising the fertilisation of its crop based ingredients, using more locally produced feed ingredients, reducing concentrations of Cu and Zn in the feed, and using wheat-based rather than maize-based feeds.     

Replacement policy in dairy herds on farms where heifers compete with cows for grassland: Part 2-Experimentation

Replacement policy is not easy to determine on dairy farms where heifers compete with cows for grassland. Using a computer simulation model of this farm situation, two factorial experiments were conducted to evaluate quantitatively the effect of different replacement rates on profitability and herd improvement.The variables changed in herds of average health and very good health were replacement rate (0·14, 0·22, 0·30), age at first calving (36, 24 months), calving index (13, 12 months) and AI sire merit (standard, premium). Initially, the experimental herd had average health, a replacement rate of 0·22, a calving index of 13 months, calved its heifers at 36 months and had been using standard bulls for many years.After 15 years, the increase in the level of a sinking fund when the age at first calving was reduced was between three and five times greater than when premium bulls were used, calving index was reduced or herd health was improved. There was a major interaction between replacement rate and age at first calving.Yield per cow was significantly reduced (P≤0·001) by reducing the age at first calving and significantly increased when premium bulls (P≤0·001) were used or when herd health was improved (P≤0·05).Some treatments were not tested as expected due to the restraining effect of a 13-month calving interval on the availability of cows for breeding pure in a seasonally calving herd.     

Factors influencing potential scale of adoption of a perennial pasture in a mixed crop-livestock farming system

Evaluating the potential scale of adoption of a technological innovation or management practice at the farm business scale can help gauge the potential size of an industry for the purposes of prioritising resources for research and development. In this paper we address the question of quantifying the potential area of adoption of a perennial pasture, lucerne (Medicago sativa L.), in dryland mixed farming systems in Australia. Lucerne pastures play a significant role in dryland farming systems in the wheat-sheep zone of southern and western Australia. While there are benefits of integrating lucerne into cropping systems there will inevitably be additional costs, and the scale of adoption of lucerne will depend largely on the increase in farm profit resulting from the introduction of lucerne. Whole-farm economic models of representative farms in the Australian wheat-sheep belt were used to determine the key drivers for the scale of adoption of lucerne.For a particular farming system the optimal area of lucerne which maximises whole-farm profit is found to depend on production, price and cost conditions. Generally, no more than 30% of a farm was allocated to lucerne according to those conditions and location of the farm. For most scenarios examined the response of profit was flat around the optimal area. This implies that lucerne could be grown on areas greater than the optimum, in order to reduce groundwater recharge (and thereby reduce the risk of dryland salinity), without greatly reducing whole-farm profit. The optimal area of lucerne in all regions was limited by the area of suitable soil types and proportion of lucerne in the most profitable lucerne-crop sequences.At all price levels assumed in this study lucerne remained as part of the optimal enterprise mix for all farm types examined. Lucerne productivity was also a major determinant of the optimal area of lucerne. The sensitivity of profit to changes in winter and/or summer production varied between regions and for different livestock enterprises. The differences were driven by the timing of energy demands and supply of feed in individual farming systems.In all regions the optimal area and profitability of lucerne varied with livestock enterprise. The analyses showed that changing from wool production to meat production enabled greater economic benefit to be realised from lucerne. This was consistent across farm types and demonstrated the value of lucerne as a source of high quality feed for finishing prime lambs in summer.The results of this study demonstrate that lucerne is profitable in a range of environments on a significant proportion of the farm area, but that this area is small relative to that required to significantly influence in its own right the environmental issue of salinity.