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The increase in average global temperatures presents a challenge for the beef industry, especially in the feedlot sector where heat stress is a major animal welfare and economic concern. Shade is one of the most practical methods to mitigate heat stress in feedlot cattle. An experiment was conducted as a completely randomized design with 1 560 Bos indicus bulls (initial BW=287 kg) where three shade structure types were used to investigate the effects of different heat stress mitigation methods on cattle growth performance, environmental, and economic outcomes using live animal data, and a partial lifecycle assessment using the Integrated Farm System Model. The live animal portion of the experiment was done once a year over a 2-year period with three pen replications per treatment per year (n = 6 per treatment). Four shade structures used were conventional shade (SC; steel shade 1.8 m 2 of shade/animal), double conventional shade (DS; steel shade 3.6 m 2 of shade/animal), dome structures without fans (DSA; 8.5 m 2 /animal with 98% solar radiation blocked), and domes with fans (DCA; DSA plus three large sized low-speed fans). Each pen held 65 bulls in an area of 570 m 2 . Live animal data were analyzed as a completely randomized design using the GLM procedure of SAS (version 9.4) with shade type as fixed effect, pen as the experimental unit, and repetition (year) considered a random effect. Cattle housed under DCA had 22 and 20 kg heavier final body BW (P < 0.05) compared to those housed under SC and DS, respectively. Final BW of DCA and DSA cattle were similar (P > 0.05). Average daily gain, feed efficiency, and hot carcass weight were greater (P < 0.05) for cattle housed under DCA compared to the rest of the shade types. Dry matter intake was not affected (P > 0.05). When treatment results were extrapolated to the annual feedlot turnover of 209,700 animals, cattle in DSA and DCA versus SC and DS had 3-8% reductions in greenhouse gas and ammonia emission intensities. Compared to SC, DCA increased profitability by $29.66/animal, followed by DSA and DS with profit increases of $5.79 and $8.90/animal, respectively. Overall, the implementation of advanced shade structures improved cattle performance and profitability while reducing the environmental impact of beef production., (Copyright © 2024. Published by Elsevier B.V.)

Waste-to-energy systems can provide a functional demonstration of the economic and environmental benefits of circularity, innovation, and reimagining existing systems. This study offers a robust quantification of the greenhouse gas (GHG) emission reduction potential of the adoption of anaerobic digestion (AD) technology on applicable large-scale dairy farms in the contiguous United States. GHG reduction estimates were developed through a robust life cycle modeling framework paired with sensitivity and uncertainty analyses. Twenty dairy configurations were modeled to capture important differences in housing and manure management practices, applicable AD technologies, regional climates, storage cleanout schedules, and methods of land application. Monte Carlo results for the 90% confidence interval illustrate the potential for AD adoption to reduce GHG emissions from the large-scale dairy industry by 2.45-3.52 MMT of CO 2 -eq per year considering biogas use only in renewable natural gas programs and as much as 4.53-6.46 MMT of CO 2 -eq per year with combined heat and power as an additional biogas use case. At the farm level, AD technology may reduce GHG emissions from manure management systems by 58.1-79.8% depending on the region. Discussion focuses on regional differences in GHG emissions from manure management strategies and the challenges and opportunities surrounding AD adoption.

Dairy farms in the United States have changed in many ways over the past 50 yr. Milk production efficiency has increased greatly, with ∼30% fewer cows producing about twice the amount of milk today. Other improvements include increases in crop yields, fuel efficiency of farm equipment, and efficiency in producing most resources used on farms (e.g. electricity, fuel, fertilizer). These improvements have led to changes in the environmental impact of farms. Through simulation of representative dairy farms in 1971 and 2020, changes in nutrient losses and farmgate life cycle assessments of greenhouse gas (GHG) emissions, fossil energy use, and blue (ground and surface) water use were determined for 6 regions and the United States. For all environmental metrics studied, intensities expressed per unit of fat- and protein-corrected milk produced were reduced, but the total effects over all farms or milk produced increased for 5 of the 13 environmental metrics. Reductions in the impacts of dairy farms in the eastern United States were offset by large increases in western regions because of a major increase in cow numbers in the West. The national average intensity of GHG emissions decreased by 42%, which gave just a 14% increase in the total GHG emissions of all dairy farms over the 50-yr period. The intensity of fossil energy use decreased by 54%, with the total for all farms decreasing by 9%. Water use related to milk production decreased in intensity by 28%, but due to the large increase in dairy production in the dry western regions that have a greater dependence on irrigated feed crops, total blue water use increased by 42%. Major pathways of nitrogen loss included ammonia volatilization, leaching, and denitrification, where total ammonia emissions related to US dairy farms increased by 29%, while leaching losses decreased by 39%, with little change in nitrous oxide emissions. Simulated nitrogen and phosphorus runoff losses totaled for all dairy farms decreased by 27% to 51% through more efficient fertilizer use, reduced tillage, and greater use of cover crops. Emissions of methane and reactive non-methane volatile organic compounds increased by 32% and 53%, respectively, due to greater use of long-term manure storage and silage stored in bunkers and piles. Although much progress has been made in improving production efficiency, continued improvements with new strategies and technologies are needed to meet the demand for dairy products and mitigate total environmental impacts, particularly in view of projected climate variability., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Pasture-based and grass-fed branding are often associated with consumer perceptions of improved human health, environmental performance and animal welfare. Here, to examine the impacts of dairy production in detail, we contrasted global observational (n = 156) data for nitrogen and phosphorus losses from land by the duration of outdoor livestock grazing in confined, grazed and hybrid systems. Observational nitrogen losses for confined systems were lowest on a productivity-but not area-basis. No differences were noted for phosphorus losses between the systems. Modelling of the three dairy systems in New Zealand, the United States and the Netherlands yielded similar results. We found insufficient evidence that grazed dairy systems have lower nutrient losses than confined ones, but trade-offs exist between systems at farm scale. The use of a hybrid system may allow for uniform distribution of stored excreta, controlled dietary intake, high productivity and mitigation of animal welfare issues arising from climatic extremes., (© 2022. The Author(s).)

Agricultural communities of New Mexico regularly redistribute manure nutrients from dairies to nearby croplands to fulfill agronomic nutrient needs and protect water quality. Yet competition for water resources can result in land use change that affects these cooperative manure transfers. Focusing on three clusters of New Mexico dairy farms and their surrounding lands (three manuresheds), we calculated the magnitude of land use changes in 2008-2019 and the balance between manure nutrient supply and crop demand in 2019 to assess how past change may predict future prospects for sustainable management. The overall magnitude of change was small, with each manureshed experiencing a different complement: an exchange of cropland and rangeland in the Roosevelt manureshed (7,975 ha rangeland to cropland; 7,624 ha cropland to rangeland), a 464-ha gain in cropland but a 1,187-ha loss of "spreadable" land (cropland, rangeland, fallow) to developed land in the Doña Ana manureshed, and relatively minor changes in the Chaves manureshed. Nutrient supply and demand were mainly in balance, but a surplus of manure phosphorus (P) in the Chaves manureshed and a thin margin of P assimilation by croplands in the Roosevelt manureshed point to the need for preserving existing croplands and understanding of effects of dairy manure on shortgrass rangeland. Our assessment suggests that an ideal scenario would entail manure being generated in landscapes with portfolios of productive lands that can sustainably use the manure nutrients to minimize environmental quality concerns and agronomic tradeoffs. Coordinated, participatory, and interdisciplinary research and planning are needed., (© 2021 The Authors. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of Hoboken, USA. This article has been contributed to by US Government employees and their work is in the public domain in the USA.)

The manureshed represents cropland needed to safely assimilate manure nutrients from an animal feeding operation. Dairy manuresheds can be contained on-farm but may need to involve additional farms that can assimilate excess nutrients. We present case studies reviewing challenges and opportunities to manureshed management in four major dairy-producing states using available information on local manuresheds. Additionally, geographic information system software was used with data from regulated Minnesota dairies to assess cropland assimilative capacities and transport needs surrounding large dairies. Manureshed requirements vary across regions, but increased import of feed and soil phosphorus accumulation constrain on-farm manure utilization across the United States. In Minnesota, a growing proportion of Jersey cattle and differences in continuous corn (Zea mays L.) vs. corn-alfafa (Medicago sativa L.) rotations contribute to the amount of land needed to absorb dairy manure nutrients. Farm-gate budgets reveal that N-based manuresheds can be contained within Idaho dairies, but P-based manuresheds extend beyond the farm. In New Mexico, relocation of surplus manure nutrients off the farm is common via informal networks, but incentives to strengthen these networks could ensure sustainable manureshed management. Evaluation of manureshed requirements in Pennsylvania is often complicated by the need for additional nutrient management planning and greater understanding of nutrient balances on the preponderance of small dairies. Nutrient imbalances with highly concentrated dairy production often lead to the need for manure transport off-farm. However, advances in herd and cropland management offer opportunities to improve on-farm nutrient efficiencies, and emerging networks and technologies promise to facilitate manure export when needed., (© 2022 The Authors. Journal of Environmental Quality © 2022 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Nutrient circularity can help supply chain participants meet sustainability targets. Across the segmented beef supply chain, opportunity exists to reinforce and introduce nutrient circularity by recycling surplus manure nutrients from cattle feedlots to lands where cattle feed is produced. We describe four datasets developed to evaluate options in U.S. and Canadian beef systems. The datasets delineate three "circular manuresheds," each encompassing a hay-grazing landscape where beef cattle are raised on grazingland and supplemented with hay grown nearby, and the distant feedlots where those cattle produce manure nutrients for potential import back to the hayfields. We selected the hay-grazing landscapes of New Mexico, USA; Florida, USA; and western Canada (Manitoba, Saskatchewan, Alberta, British Columbia) because of their significant grazingland production and potential to substitute feedlot manure for commercial fertilizer on hayfields. In each circular manureshed, the manure nutrients from major feedlot destinations could supply a considerable proportion of the P used by hay for grazing cattle: 34% of the P requirements in New Mexico, 36% in Florida, and 6% in western Canada. The average distance to return the resource was 647 km for New Mexico, 1,884 km for Florida, and 1,587 km for western Canada. These magnitudes and distances suggest that the New Mexico circular manureshed may be the most economically viable in the current agri-food system, but this reflects only part of a greater, multi-factor assessment of tradeoffs. The circular manureshed concept provides a platform for simultaneous consideration of competing factors for sustainability via circularity., (© 2022 Her Majesty the Queen in Right of Canada. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

The objective of this study was to determine the impact of beef production systems utilizing additive combinations of growth promotant technologies on animal and carcass performance and environmental outcomes. Crossbred steer calves ( n =120) were stratified by birth date, birth weight, and dam age and assigned randomly to one of four treatments: 1) no technology (NT; control), 2) antibiotic treated (ANT; NT plus therapeutic antibiotics and monensin and tylosin), 3) implant treated (IMP; ANT plus a series of 3 implants, and 4) beta-agonist treated (BA; IMP plus ractopamine-HCl for the last 30 d prior to harvest). Weaned steers were fed in confinement (dry lot) and finished in an individual feeding system to collect performance data. At harvest, standard carcass measures were collected and the United States Department of Agriculture (USDA) Yield Grade and Quality Grade were determined. Information from the cow-calf, growing, and finishing phases were used to simulate production systems using the USDA Integrated Farm System Model, which included a partial life cycle assessment of cattle production for greenhouse gas (GHG) emissions, fossil energy use, water use, and reactive N loss. Body weight in suckling, growing, and finishing phases as well as hot carcass weight was greater ( P < 0.05) for steers that received implants (IMP and BA) than non-implanted steers (NT and ANT). The average daily gain was greater ( P < 0.05) for steers that received implants (IMP and BA) than non-implanted steers during the suckling and finishing phases, but no difference ( P = 0.232) was detected during the growing phase. Dry matter intake and gain:feed were greater ( P < 0.05) for steers that received implants than non-implanted steers during the finishing phase. Steers that received implants responded ( P < 0.05) with a larger loin muscle area, less kidney pelvic and heart fat, advanced carcass maturity, reduced marbling scores, and a greater percentage of carcasses in the lower third of the USDA Choice grade. This was offset by a lower percentage of USDA Prime grading carcasses compared with steers receiving no implants. Treatments did not influence ( P > 0.05) USDA Yield grade. The life cycle assessment revealed that IMP and BA treatments reduced GHG emissions, energy use, water use, and reactive nitrogen loss compared to NT and ANT. These data indicate that growth promoting technologies increase carcass yield while concomitantly reducing carcass quality and environmental impacts., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Dairy farms have been under pressure to reduce negative environmental impacts while remaining profitable during times with volatile milk and commodity prices. Double cropping has been promoted to reduce negative environmental impacts and increase total dry matter yield per hectare. Three dairy farms that double cropped winter annuals and corn were selected from northern and western Pennsylvania. Data were collected from recorded crop and dairy records and financial data for 2016 and 2017. Farms ranged in size from 336 to 511 ha with 233 to 663 cows. Data were used to set parameters for the Integrated Farm System Model, which was then used to simulate 8 scenarios for each farm: current operation; 0, 50, and 100% of corn hectares double cropped; 30% feed price increase with and without double cropping; and 30% feed price decrease with and without double cropping at the farm's current level of double cropping. A 20-yr time period, using weather data that was representative of the actual farms, was used in the Integrated Farm System Model simulation to produce both financial and environmental outputs. Double cropping winter annuals and corn silage increased dry matter yield per hectare by 19%, when comparing 0 to 100% of the corn area double cropped. With all corn land double cropped, net return to management per hundredweight (45.36 kg) of milk increased by 1.8%, N leached per hectare per year decreased by an average of 4.5%, and phosphorus loss was reduced by an average of 9.2% across farms. When feed prices increased by 30%, double cropping increased net return over feed cost and net return to management by 1.6 and 2.2%, respectively, across farms. When feed prices decreased by 30%, double cropping decreased net return over feed cost and net return to management by smaller amounts of 0.13% and 0.11%, respectively, across farms. Modeling indicated that double cropping winter annuals with corn silage can have both environmental and economic benefits when winter-annual silage yields are enough to cover expenses., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

A comprehensive, yet in depth, assessment is needed of the environmental impacts of dairy farms at regional and national scales to better track improvements made by the industry. With Pennsylvania as an example, a method using process-level simulation and cradle-to-farm gate life cycle assessment was developed and used to assess important environmental footprints of dairy farms within a state. Representative dairy farms of various sizes and management practices throughout 7 regions of the state were simulated with the Integrated Farm System Model. Environmental footprints varied widely among farms, with this variation influenced primarily by soil characteristics and climate and secondarily by farm management. Therefore, prescriptive mitigation strategies for individual farms are more effective than uniform enforcement of specific strategies across the state. Footprints for the whole state were determined by totaling values among farms and regions based on the amounts of milk produced by each. Pennsylvania dairy farms were determined to emit 4,555 with an uncertainty of ±415 Gg of CO 2 equivalent of greenhouse gas with an intensity of 0.99 ± 0.09 kg of CO 2 equivalent/kg of fat- and protein-corrected milk (FPCM) produced. Fossil energy consumption was 12,324 ± 1,946 TJ or 2.69 ± 0.42 MJ/kg of FPCM. Blue (nonprecipitation) water consumption was 64.1 ± 13.5 Tg with an intensity of 14.0 ± 3.0 kg/kg of FPCM. A total of all forms of reactive N loss was 43.2 ± 5.0 Gg with an intensity of 9.4 ± 1.1 g/kg of FPCM. These metrics were equivalent to 1.6% of the greenhouse gas emissions, 0.4% of fossil energy use, and 0.8% of fresh water consumption reported for the state. Thus, greenhouse gas emissions, fossil energy use, and blue water use associated with dairy farm production are relatively small compared with total estimates for the state. Perhaps the greatest environmental concern is that of ammonia emission, where dairy farms accounted for about half the estimated emissions of the state. This method can be applied to assessments of the dairy industry at larger regional and national scales., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Cost-effective heat mitigation strategies are imperative for maintaining milk production and dairy farm profitability in the U.S. with projected climate change. This study investigated the cost-effectiveness of four heat abatement strategies, including Minimal (open barn or shading), Moderate (forced ventilation), High (fans and misting), and Intense (air conditioning). Heat stress and subsequent impacts on milk production per cow were predicted across nine climatic regions in the U.S. for early (2015 to 2034), mid (2045 to 2064) and late (2081 to 2100) 21st century, using downscaled climate projections. Heat abatements were used to adjust predicted milk production losses and illustrate the potential to reduce milk production losses due to heat stress. Economic analysis included a cost-benefit ratio calculation associated with the implementation of each heat abatement. Results showed that milk production losses were expected to accelerate across the U.S. at a mean rate of 174±7 kg/cow/decade, with the fastest rate in the Southeast region. Relative to Minimal heat abatement, Moderate, High, and Intense heat abatements increased annual milk production per cow by 3%, 4%, and 6% during early-21st century, 3%, 6%, and 11% during mid-21st century, and 3%, 8%, and 21% during late-21st century, respectively. The cost effectiveness of different heat abatement strategies generally increased with subsequently stronger heat abatements. In mid- and late-21st century, mean annual net values of High and Intense heat stress abatement implementation approached -$30 to $190 /cow and -$20 to $590 /cow, respectively, with the largest net annual benefit in late-21st century under Intense abatement. Findings from the study demonstrate the value of using downscaled climate projections to shed light on local and regional strategies to abate heat stress on cattle and mitigate potential milk production losses due to climate change., Competing Interests: The authors have declared that no competing interests exist.

Nutrient management on US dairy farms must balance an array of priorities, some of which conflict. To illustrate nutrient management challenges and opportunities across the US dairy industry, the USDA Agricultural Research Service Dairy Agroecosystems Working Group (DAWG) modeled 8 confinement and 2 grazing operations in the 7 largest US dairy-producing states using the Integrated Farm System Model (IFSM). Opportunities existed across all of the dairies studied to increase on-farm feed production and lower purchased feed bills, most notably on large dairies (>1,000 cows) with the highest herd densities. Purchased feed accounted for 18 to 44% of large dairies' total operating costs compared with 7 to 14% on small dairies (<300 milk cows) due to lower stocking rates. For dairies with larger land bases, in addition to a reduction in environmental impact, financial incentives exist to promote prudent nutrient management practices by substituting manure nutrients or legume nutrients for purchased fertilizers. Environmental priorities varied regionally and were principally tied to facility management for dry-lot dairies of the semi-arid western United States (ammonia-N emissions), to manure handling and application for humid midwestern and eastern US dairies (nitrate-N leaching and P runoff), and pasture management for dairies with significant grazing components (nitrous oxide emissions). Many of the nutrient management challenges identified by DAWG are beyond slight modifications in management and require coordinated solutions to ensure an environmentally and economically sustainable US dairy industry., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).)

Dairy farms have been identified as an important source of greenhouse gas emissions. Within the farm, important emissions include enteric CH 4 from the animals, CH 4 and N 2 O from manure in housing facilities during long-term storage and during field application, and N 2 O from nitrification and denitrification processes in the soil used to produce feed crops and pasture. Models using a wide range in level of detail have been developed to represent or predict these emissions. They include constant emission factors, variable process-related emission factors, empirical or statistical models, mechanistic process simulations, and life cycle assessment. To fully represent farm emissions, models representing the various emission sources must be integrated to capture the combined effects and interactions of all important components. Farm models have been developed using relationships across the full scale of detail, from constant emission factors to detailed mechanistic simulations. Simpler models, based upon emission factors and empirical relationships, tend to provide better tools for decision support, whereas more complex farm simulations provide better tools for research and education. To look beyond the farm boundaries, life cycle assessment provides an environmental accounting tool for quantifying and evaluating emissions over the full cycle, from producing the resources used on the farm through processing, distribution, consumption, and waste handling of the milk and dairy products produced. Models are useful for improving our understanding of farm processes and their interacting effects on greenhouse gas emissions. Through better understanding, they assist in the development and evaluation of mitigation strategies for reducing emissions and improving overall sustainability of dairy farms., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).)

Corn has been a pillar of American agriculture for decades and continues to receive much attention from the scientific community for its potential to meet the food, feed and fuel needs of a growing human population in a changing climate. By midcentury, global temperature increase is expected to exceed 2°C where local effects on heat, cold and precipitation extremes will vary. The Northeast United States is a major dairy producer, corn consumer, and is cited as the fastest warming region in the contiguous U.S. It is important to understand how key agronomic climate variables affect corn growth and development so that adaptation strategies can be tailored to local climate changes. We analyzed potential local effects of climate change on corn growth and development at three major dairy locations in the Northeast (Syracuse, New York; State College, Pennsylvania and Landisville, Pennsylvania) using downscaled projected climate data (2000-2100) from nine Global Climate Models under two emission pathways (Representative Concentration Pathways (RCP) 4.5 and 8.5). Our analysis indicates that corn near the end of the 21st century will experience fewer spring and fall freezes, faster rate of growing degree day accumulation with a reduction in time required to reach maturity, greater frequencies of daily high temperature ≥35°C during key growth stages such as silking-anthesis and greater water deficit during reproductive (R1-R6) stages. These agronomic anomalies differ between the three locations, illustrating varying impacts of climate change in the more northern regions vs. the southern regions of the Northeast. Management strategies such as shifting the planting dates based on last spring freeze and irrigation during the greatest water deficit stages (R1-R6) will partially offset the projected increase in heat and drought stress. Future research should focus on understanding the effects of global warming at local levels and determining adaptation strategies that meet local needs., Competing Interests: The authors have declared that no competing interests exist.

Nitrous oxide (NO) emissions from concentrated animal feeding operations, including cattle feedyards, have become an important research topic. However, there are limitations to current measurement techniques, uncertainty in the magnitude of feedyard NO fluxes, and a lack of effective mitigation methods. The objective of this review was to assess NO emission from cattle feedyards, including comparison of measured and modeled emission rates, discussion of measurement methods, and evaluation of mitigation options. Published annual per capita flux rates for beef cattle feedyards and open-lot dairies were highly variable and ranged from 0.002 to 4.3 kg NO animal yr. On an area basis, published emission rates ranged from 0 to 41 mg NO m h. From these studies and Intergovernmental Panel on Climate Change emission factors, calculated daily per capita NO fluxes averaged 18 ± 10 g NO animal d (range, 0.04-67 g NO animal d). This variation was due to inconsistency in measurement techniques as well as irregularity in NO production and emission attributable to management, animal diet, and environmental conditions. Based on this review, it is clear that the magnitude and dynamics of NO emissions from open-lot cattle systems are not well understood. Further research is required to quantify feedyard NO fluxes and develop cost-effective mitigation methods., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

A comprehensive national assessment of the sustainability of beef is being conducted by the U.S. beef industry. The first of 7 regions to be analyzed is Kansas, Oklahoma, and Texas. A survey and visits conducted throughout the region provided data on common production practices. From these data, representative ranch and feedyard operations were defined and simulated for the varying climate and soil conditions throughout the region using the Integrated Farm System Model. These simulations predicted environmental impacts of each operation including cradle-to-farm gate footprints for greenhouse gas emissions, fossil-based energy use, nonprecipitation water use, and reactive N loss. Individual ranch and feedyard operations were linked to form 28 representative production systems. A weighted average of the production systems was used to determine the environmental footprints for the region where weighting factors were developed based on animal numbers reported in the survey and agricultural statistics data. Along with the traditional beef production systems, Holstein steer and cull cow production from the dairy industry in the region were also modeled and included. The carbon footprint of all beef produced was 18.3 ± 1.7 kg CO2 equivalents (CO2e)/kg carcass weight (CW) with the range in individual production systems being 13 to 25 kg CO2e/kg CW. Energy use, water use, and reactive N loss were 51 ± 4.8 MJ/kg CW, 2,470 ± 455 L/kg CW, and 138 ± 12 g N/kg CW, respectively. The major portion of each footprint except water use was associated with the cow-calf phase; most of the nonprecipitation water use was attributed to producing feed for the finishing phase. These data provide a baseline for comparison as new technologies and strategies are developed and implemented to improve the sustainability of cattle production. Production information also will be combined with processing, marketing, and consumer data to complete a comprehensive life cycle assessment of beef.

In dairy production systems, tradeoffs can occur between fertilizer N applications and crop N use, feed N consumption and manure N excretion, and environmental impacts. This paper examines (i) how stocking rates affect N imports and management on dairy farms, N use efficiency (NUE; i.e., the amount of applied N incorporated into product N), and N loss; (ii) how reductions in fertilizer N and feed N may affect crop and milk production, NUE, and N loss; and (iii) why tradeoffs in N use outcomes should be considered when attempting to enhance overall NUE and reduce N loss. The Integrated Farm Simulation Model simulations of two representative dairy farm types and analyses of regional studies, long-term field experiments, and cow nutrition trials were used to demonstrate that (i) stocking rate affects cropping patterns, fertilizer and feed imports, and N loss; (ii) although fertilizer N reductions of 20 kg N ha may reduce slightly the crude protein (CP) content of corn silage (which would require purchase of additional CP supplements), this practice should not affect long-term corn yield but would reduce nitrate (NO) and nitrous oxide (NO) losses by 13 to 38%; (iii) dietary CP could be reduced on many dairy farms, which would not affect milk production but would reduce ammonia (NH) and NO emissions by 15 to 43%; and (iv) greater recognition of the tradeoffs in N use and N loss are needed to provide a better understanding of the potentials to enhance overall NUE and reduce environmental N loss from dairy production systems., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

The objective of this work was to evaluate the effects of biological and chemical silage additives on the production of volatile organic compounds (VOC; methanol, ethanol, 1-propanol, methyl acetate, and ethyl acetate) within corn silage. Recent work has shown that silage VOC can contribute to poor air quality and reduce feed intake. Silage additives may reduce VOC production in silage by inhibiting the activity of bacteria or yeasts that produce them. We produced corn silage in 18.9-L bucket silos using the following treatments: (1) control (distilled water); (2) Lactobacillus buchneri 40788, with 400,000 cfu/g of wet forage; (3) Lactobacillus plantarum MTD1, with 100,000 cfu/g; (4) a commercial buffered propionic acid-based preservative (68% propionic acid, containing ammonium and sodium propionate and acetic, benzoic, and sorbic acids) at a concentration of 1 g/kg of wet forage (0.1%); (5) a low dose of potassium sorbate at a concentration of 91 mg/kg of wet forage (0.0091%); (6) a high dose of potassium sorbate at a concentration of 1g/kg of wet forage (0.1%); and (7) a mixture of L. plantarum MTD1 (100,000 cfu/g) and a low dose of potassium sorbate (91 mg/kg). Volatile organic compound concentrations within silage were measured after ensiling and sample storage using a headspace gas chromatography method. The high dose of potassium sorbate was the only treatment that inhibited the production of multiple VOC. Compared with the control response, it reduced ethanol by 58%, ethyl acetate by 46%, and methyl acetate by 24%, but did not clearly affect production of methanol or 1-propanol. The effect of this additive on ethanol production was consistent with results from a small number of earlier studies. A low dose of this additive does not appear to be effective. Although it did reduce methanol production by 24%, it increased ethanol production by more than 2-fold and did not reduce the ethyl acetate concentration. All other treatments increased ethanol production at least 2-fold relative to the control, and L. buchneri addition also increased the 1-propanol concentration to approximately 1% of dry matter. No effects of any treatments on fiber fractions or protein were observed. However, L. buchneri addition resulted in slightly more ammonia compared with the control. If these results hold under different conditions, a high dose of potassium sorbate will be an effective treatment for reducing VOC production in and emission from silage. Regulations aimed at reducing VOC emission could be ineffective or even increase emission if they promote silage additives without recognition of different types of additives., (Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Urinary urea N (UUN) is the principal nitrogen (N) source controlling emissions of ammonia (NH) and nitrous oxide (NO) from dairy manure. The objectives of this study were (i) to study the integrative nature of dietary crude protein (CP) management, secretion of milk urea N (MUN), excretion of UUN, and N emissions from dairy production systems; (ii) to evaluate how associative changes in dietary CP, MUN, and UUN affect atmospheric N emissions from dairy farms; and (iii) to discuss some of the challenges and opportunities to an expanded use of MUN to enhance dietary CP use and decrease UUN excretion and N emissions from dairy farms. Milk urea N records of 37,889 cows in 197 herds in Wisconsin revealed that approximately one half of tested cows were likely consuming dietary CP in excess of requirement. Farm simulations were used to quantify the effect of dietary CP on whole-farm N emissions. At a statewide average MUN of 12.5 mg dL, 48 to 87% of UUN was emitted as NH, with the lowest loss from pasture-based farms and the greatest loss from tie-stall farms. Each 1 mg dL decrease of MUN (range, 16-10 mg dL) provided an associated daily decrease in UUN of 16.6 g per cow, which decreased NH and NO emissions from manure by 7 to 12%. Although more site-specific information is required on herd MUN-UUN relationships and more a reliable interpretation of MUN assay results is needed, monitoring of MUN may be used to enhance dietary CP use and to reduce UUN excretion and N emissions from Wisconsin dairy farms., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

Ammonia (NH) volatilization from manure in beef cattle feedyards results in loss of agronomically important nitrogen (N) and potentially leads to overfertilization and acidification of aquatic and terrestrial ecosystems. In addition, NH is involved in the formation of atmospheric fine particulate matter (PM), which can affect human health. Process-based models have been developed to estimate NH emissions from various livestock production systems; however, little work has been conducted to assess their accuracy for large, open-lot beef cattle feedyards. This work describes the extension of an existing process-based model, the Integrated Farm Systems Model (IFSM), to include simulation of N dynamics in this type of system. To evaluate the model, IFSM-simulated daily per capita NH emission rates were compared with emissions data collected from two commercial feedyards in the Texas High Plains from 2007 to 2009. Model predictions were in good agreement with observations and were sensitive to variations in air temperature and dietary crude protein concentration. Predicted mean daily NH emission rates for the two feedyards had 71 to 81% agreement with observations. In addition, IFSM estimates of annual feedyard emissions were within 11 to 24% of observations, whereas a constant emission factor currently in use by the USEPA underestimated feedyard emissions by as much as 79%. The results from this study indicate that IFSM can quantify average feedyard NH emissions, assist with emissions reporting, provide accurate information for legislators and policymakers, investigate methods to mitigate NH losses, and evaluate the effects of specific management practices on farm nutrient balances., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

Ammonia (NH) emissions vary considerably among farms as influenced by climate and management. Because emission measurement is difficult and expensive, process-based models provide an alternative for estimating whole farm emissions. A model that simulates the processes of NH formation, speciation, aqueous-gas partitioning, and mass transfer was developed and incorporated in a whole farm simulation model (the Integrated Farm System Model). Farm sources included manure on the floor of the housing facility, manure in storage (if used), field-applied manure, and deposits on pasture (if grazing is used). In a comprehensive evaluation of the model, simulated daily, seasonal, and annual emissions compared well with data measured over 2 yr for five free stall barns and two manure storages on dairy farms in the eastern United States. In a further comparison with published data, simulated and measured barn emissions were similar over differing barn designs, protein feeding levels, and seasons of the year. Simulated emissions from manure storage were also highly correlated with published emission data across locations, seasons, and different storage covers. For field applied manure, the range in simulated annual emissions normally bounded reported mean values for different manure dry matter contents and application methods. Emissions from pastures measured in northern Europe across seasons and fertilization levels were also represented well by the model. After this evaluation, simulations of a representative dairy farm in Pennsylvania illustrated the effects of animal housing and manure management on whole farm emissions and their interactions with greenhouse gas emissions, nitrate leaching, production costs, and farm profitability., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

A methodology was developed and used to determine environmental footprints of beef cattle produced at the U.S. Meat Animal Research Center (MARC) in Clay Center, NE, with the goal of quantifying improvements achieved over the past 40 yr. Information for MARC operations was gathered and used to establish parameters representing their production system with the Integrated Farm System Model. The MARC farm, cow-calf, and feedlot operations were each simulated over recent historical weather to evaluate performance, environmental impact, and economics. The current farm operation included 841 ha of alfalfa and 1,160 ha of corn to produce feed predominately for the beef herd of 5,500 cows, 1,180 replacement cattle, and 3,724 cattle finished per year. Spring and fall cow-calf herds were fed on 9,713 ha of pastureland supplemented through the winter with hay and silage produced by the farm operation. Feedlot cattle were backgrounded for 3 mo on hay and silage with some grain and finished over 7 mo on a diet high in corn and wet distillers grain. For weather year 2011, simulated feed production and use, energy use, and production costs were within 1% of actual records. A 25-yr simulation of their current production system gave an average annual carbon footprint of 10.9±0.6 kg of CO2 equivalent units per kg BW sold, and the energy required to produce that beef (energy footprint) was 26.5±4.5 MJ/kg BW. The annual water required (water footprint) was 21,300±5,600 L/kg BW sold, and the water footprint excluding precipitation was 2,790±910 L/kg BW. The simulated annual cost of producing their beef was US$2.11±0.05/kg BW. Simulation of the production practices of 2005 indicated that the inclusion of distillers grain in animal diets has had a relatively small effect on environmental footprints except that reactive nitrogen loss has increased 10%. Compared to 1970, the carbon footprint of the beef produced has decreased 6% with no change in the energy footprint, a 3% reduction in the reactive nitrogen footprint, and a 6% reduction in the real cost of production. The water footprint, excluding precipitation, has increased 42% due to greater use of irrigated corn production. This proven methodology provides a means for developing the production data needed to support regional and national full life cycle assessments of the sustainability of beef.

The farm level is the most appropriate scale for evaluating options for mitigating greenhouse gas (GHG) emissions, because the farm represents the unit at which management decisions in livestock production are made. To date, a number of whole farm modelling approaches have been developed to quantify GHG emissions and explore climate change mitigation strategies for livestock systems. This paper analyses the limitations and strengths of the different existing approaches for modelling GHG mitigation by considering basic model structures, approaches for simulating GHG emissions from various farm components and the sensitivity of GHG outputs and mitigation measures to different approaches. Potential challenges for linking existing models with the simulation of impacts and adaptation measures under climate change are explored along with a brief discussion of the effects on other ecosystem services.

Beef production is a recognized source of greenhouse gas (GHG) and ammonia (NH(3)) emissions; however, little information exists on the net emissions from beef production systems. A partial life cycle assessment (LCA) was conducted using the Integrated Farm System Model (IFSM) to estimate GHG and NH(3) emissions from representative beef production systems in California. The IFSM is a process-level farm model that simulates crop growth, feed production and use, animal growth, and the return of manure nutrients back to the land to predict the environmental impacts and economics of production systems. Ammonia emissions are determined by summing the emissions from animal housing facilities, manure storage, field applied manure, and direct deposits of manure on pasture and rangeland. All important sources and sinks of methane, nitrous oxide, and carbon dioxide are predicted from primary and secondary emission sources. Primary sources include enteric fermentation, manure, cropland used in feed production, and fuel combustion. Secondary emissions occur during the production of resources used on the farm, which include fuel, electricity, machinery, fertilizer, and purchased animals. The carbon footprint is the net exchange of all GHG in carbon dioxide equivalent (CO(2)e) units per kg of HCW produced. Simulated beef production systems included cow-calf, stocker, and feedlot phases for the traditional British beef breeds and calf ranch and feedlot phases for Holstein steers. An evaluation of differing production management strategies resulted in ammonia emissions ranging from 98 ± 13 to 141 ± 27 g/kg HCW and carbon footprints of 10.7 ± 1.4 to 22.6 ± 2.0 kg CO(2)e/kg HCW. Within the British beef production cycle, the cow-calf phase was responsible for 69 to 72% of total GHG emissions with 17 to 27% from feedlot sources. Holstein steers that entered the beef production system as a by-product of dairy production had the lowest carbon footprint because the emissions associated with their mothers were primarily attributed to milk rather than meat production. For the Holstein system, the feedlot phase was responsible for 91% of the total GHG emission, while the calf-ranch phase was responsible for 7% with the remaining 2% from transportation. This simulation study provides baseline emissions data for California beef production systems and indicates where mitigation strategies can be most effective in reducing emissions.

Increased animal performance is suggested as one of the most effective mitigation strategies to decrease greenhouse gas (GHG) and ammonia (NH(3)) emissions from livestock production per unit of product produced. Little information exists, however, on the effects of increased animal productivity on the net decrease in emission from beef production systems. A partial life cycle assessment (LCA) was conducted using the Integrated Farm System Model (IFSM) to estimate GHG and NH(3) emissions from representative beef production systems in California that use various management technologies to enhance animal performance. The IFSM is a farm process model that simulates crop growth, feed production, animal performance, and manure production and handling through time to predict the performance, economics, and environmental impacts of production systems. The simulated beef production systems compared were 1) Angus-natural, with no use of growth-enhancing technologies, 2) Angus-implant, with ionophore and growth-promoting implant (e.g., estrogen/trenbolone acetate-based) application, 3) Angus-ß2-adrenergic agonists (BAA; e.g., zilpaterol), with ionophore, growth-promoting implant, and BAA application, 4) Holstein-implant, with growth implant and ionophore application, and 5) Holstein-BAA, with ionophore, growth implant, and BAA use. During the feedlot phase, use of BAA decreased NH(3) emission by 4 to 9 g/kg HCW, resulting in a 7% decrease in NH(3) loss from the full production system. Combined use of ionophore, growth implant, and BAA treatments decreased NH(3) emission from the full production system by 14 g/kg HCW, or 13%. The C footprint of beef was decreased by 2.2 kg carbon dioxide equivalent (CO(2)e)/kg HCW using all the growth-promoting technologies, and the Holstein beef footprint was decreased by 0.5 kg CO(2)e/kg HCW using BAA. Over the full production systems, these decreases were relatively small at 9% and 5% for Angus and Holstein beef, respectively. The growth-promoting technologies we evaluated are a cost-effective way to mitigate GHG and NH(3) emissions, but naturally managed cattle can bring a similar net return to Angus cattle treated with growth-promoting technologies when sold at an 8% greater premium price.

Alternative methods for applying livestock manure to no-till soils involve environmental and economic trade-offs. A process-level farm simulation model (Integrated Farm System Model) was used to evaluate methods for applying liquid dairy (Bos taurus L.) and swine (Sus scrofa L.) manure, including no application, broadcast spreading with and without incorporation by tillage, band application with soil aeration, and shallow disk injection. The model predicted ammonia emissions, nitrate leaching, and phosphorus (P) runoff losses similar to those measured over 4 yr of field trials. Each application method was simulated over 25 yr of weather on three Pennsylvania farms. On a swine and cow-calf beef operation under grass production, shallow disk injection increased profit by $340 yr(-1) while reducing ammonia nitrogen and soluble P losses by 48 and 70%, respectively. On a corn (Zea mays L.)-and-grass-based grazing dairy farm, shallow disk injection reduced ammonia loss by 21% and soluble P loss by 76% with little impact on farm profit. Incorporation by tillage and band application with aeration provided less environmental benefit with a net decrease in farm profit. On a large corn-and-alfalfa (Medicago sativa L.)-based dairy farm where manure nutrients were available in excess of crop needs, incorporation methods were not economically beneficial, but they provided environmental benefits with relatively low annual net costs ($13 to $18 cow). In all farming systems, shallow disk injection provided the greatest environmental benefit at the least cost or greatest profit for the producer. With these results, producers are better informed when selecting manure application equipment.

Greenhouse gas (GHG) emissions and their potential effect on the environment has become an important national and international issue. Dairy production, along with all other types of animal agriculture, is a recognized source of GHG emissions, but little information exists on the net emissions from dairy farms. Component models for predicting all important sources and sinks of CH(4), N(2)O, and CO(2) from primary and secondary sources in dairy production were integrated in a software tool called the Dairy Greenhouse Gas model, or DairyGHG. This tool calculates the carbon footprint of a dairy production system as the net exchange of all GHG in CO(2) equivalent units per unit of energy-corrected milk produced. Primary emission sources include enteric fermentation, manure, cropland used in feed production, and the combustion of fuel in machinery used to produce feed and handle manure. Secondary emissions are those occurring during the production of resources used on the farm, which can include fuel, electricity, machinery, fertilizer, pesticides, plastic, and purchased replacement animals. A long-term C balance is assumed for the production system, which does not account for potential depletion or sequestration of soil carbon. An evaluation of dairy farms of various sizes and production strategies gave carbon footprints of 0.37 to 0.69kg of CO(2) equivalent units/kg of energy-corrected milk, depending upon milk production level and the feeding and manure handling strategies used. In a comparison with previous studies, DairyGHG predicted C footprints similar to those reported when similar assumptions were made for feeding strategy, milk production, allocation method between milk and animal coproducts, and sources of CO(2) and secondary emissions. DairyGHG provides a relatively simple tool for evaluating management effects on net GHG emissions and the overall carbon footprint of dairy production systems.

In 2008, corn grain prices rose $115/t of DM above the 2005 average. Such an increase creates tight marginal profits for small (<100) and medium-sized (100 to 199) dairy farms in the northeastern United States importing corn grain as animal feed supplement. Particularly in New York State, dairy farmers are attempting to avoid or minimize profit losses by growing more corn silage and reducing corn grain purchases. This study applies the Integrated Farm Systems Model to 1 small and 1 medium-sized New York State dairy farm to predict 1) sediment and P loss impacts from expanding corn fields, 2) benefits of no-till or cover cropping on corn fields, and 3) alternatives to the economic challenge of the current farming system as the price ratio of milk to corn grain continues to decline. Based on the simulation results, expanding corn silage production by 3% of the cultivated farm area increased sediment and sediment-bound P losses by 41 and 18%, respectively. Implementing no-till controlled about 84% of the erosion and about 75% of the sediment-bound P that would have occurred from the conventionally tilled, expanded corn production scenario. Implementing a conventionally tilled cover crop with the conventionally tilled, expanded corn production scenario controlled both erosion and sediment-bound P, but to a lesser extent than no-till corn with no cover crop. However, annual farm net return using cover crops was slightly less than when using no-till. Increasing on-farm grass productivity while feeding cows a high-quality, high-forage diet and precise dietary P levels offered dual benefits: 1) improved farm profitability from reduced purchases of dietary protein and P supplements, and 2) decreased runoff P losses from reduced P-levels in applied manure. Moreover, alternatives such as growing additional small grains on marginal lands and increasing milk production levels demonstrated great potential in increasing farm profitability. Overall, it is crucial that conservation measures such as no-till and cover cropping be implemented on new or existing corn lands as these areas often pose the highest threat for P losses through runoff. Although alternatives that would likely provide the largest net profit were evaluated one at a time to better quantify their individual impacts, combinations of these strategies, such as no-till corn plus a minimum-till cover crop, are recommended whenever feasible.

The current market demand and price for organic milk is encouraging dairy producers, particularly those on smaller farms, to consider organic production as a means for improving the economic viability of their operations. Organic production systems vary widely in scale, in practices, and across agroclimatic settings. Within this context, case studies of 4 actual organic dairy farms were used to characterize existing systems in Pennsylvania. Based on data from these farms, a whole-farm simulation model (Integrated Farm System Model) was used to compare 4 production systems representing organic grass, organic crop, conventional crop with grazing, and conventional confinement production. The performance of each of these systems was simulated over each year of 25 yr of central Pennsylvania weather data. Simulation results indicated that farm level accumulation of soil P and K may be a concern on organic farms that use poultry manure as a primary crop nutrient source, and that erosion and runoff loss of P may be of concern on organic farms producing annual crops because more tillage is required for weed control. Whole-farm budgets with prices that reflect recent conditions showed an economic advantage for organic over conventional production. A sensitivity analysis showed that this economic advantage depended on a higher milk price for producers of organic milk and was influenced by the difference in milk production maintained by herds using organic and conventional systems. Factors found to have little effect on the relative profitability of organic over conventional production included the differences between organic and conventional prices for seed, chemicals, forage, and animals and the overall costs or prices assumed for organic certification, machinery, pasture fencing, fuel, and labor. Thus, at the current organic milk price, relative to other prices, the case study organic production systems seem to provide an option for improving the economic viability of dairy operations of the scale considered in Pennsylvania. To motivate transition to organic systems, the economic advantage found requires the persistence of a substantial difference between conventional and organic raw milk prices.

Structural best management practices were implemented throughout the Cannonsville Reservoir Watershed (CRW) in an effort to reduce P losses to the reservoir. Yet long-term water quality control efforts within CRW are hindered by continuous P build-up in the soils resulting from dairy farm P imports exceeding exports. Addressing the P imbalance problems and maintaining economic viability of the farms requires a system-level redesign of farm management. One possible innovative strategy, precision feed management (PFM), reduces soil-P build-up by limiting feed and fertilizer purchases, and increasing high-quality homegrown forage production. This study applied the integrated farm system model (IFSM) to 2 CRW dairy farms to quantify the benefits of a PFM farm planning strategy in controlling P imbalance problems, and maintaining farm profit-ability and reducing off-farm P losses. The IFSM accurately simulated the 2 farms based on farm data supplied by farm planners; these scenarios were used as the baseline conditions. The IFSM simulations of more accurate feeding of P (based on P required in animal diets) integrated with increased productivity of grass-forage and increased proportion of forage in the diet reduced the P imbalance of 1 farm from 5.3 to 0.5 kg/ ha and from 9.6 to 0.0 kg/ha for the second farm. For both farms, soluble P lost to the environment was reduced by 18%. Feed supplement purchases declined by 7.5 kg/cow per year for dietary mineral P, and by 1.04 and 1.29 t/cow per year for protein concentrates through adoption of the PFM system. Moreover, when a land management practice of converting corn to grass was coupled with the precision feeding of P and improved forage management, IFSM predicted reductions of 5.8 and 9.3 kg/ha of converted land sediment-bound P in erosion loss each year. The model predicted slight purchase increases in corn grain to offset reductions in corn silage production and feeding rates, but no appreciable change in the farm P balance due to land conversion. The model-based studies conducted on a farm-by-farm basis complement farm planning efforts in exploring innovative farming systems. Moreover, the results set a benchmark for potential benefits of PFM strategies, economically and environmentally.

More efficient and economical production systems are needed to improve the sustainability of dairy farms. One concept to consider is using perennial cows. Perennial cows are those that maintain a relatively high milk production for >or=2 yr without going through the typical dry period followed by calving. Farm records show that some cows have produced over 20 kg/d after 4 yr of continuous lactation. A farm simulation model was used to evaluate the long-term performance, environmental impact, and economics of a conceptual perennial cow production system on a typical dairy farm in Pennsylvania. Compared with a traditional 100-cow farm with replacement heifers produced on the farm, a perennial herd of 100 cows and purchased replacements provided environmental benefit but sustained a substantial economic loss. However, increasing the perennial herd to 128 cows better utilized the feed produced on the farm. Compared with the traditional 100-cow farm, use of the perennial 128-cow herd reduced supplemental protein and mineral feed purchases by 38%, increased annual milk sales by 21%, reduced nitrogen losses by 17%, maintained a phosphorus balance, and increased annual net return to farm management by 3200 dollars. A traditional 120-cow dairy farm with purchased replacements also used a similar amount of farm-produced feed. Compared with this option, the farm with 128 perennial cows reduced protein and mineral feed purchases by 36%, maintained similar annual milk sales, increased manure production by 7%, reduced N losses by 10%, and increased annual net return by 12,700 dollars. The economic feasibility of the perennial-cow dairy farm was very sensitive to the milk production maintained by the perennial herd and market prices for milk and perennial replacement animals. The analysis was relatively insensitive to the assumed useful life of perennial cows as long as they could be maintained in the herd for at least 3 yr. Thus, a perennial cow production system can improve the economic and environmental sustainability of a traditional dairy farm if a similar level in annual milk production per cow can be maintained.

A beef herd submodel was created for integration with other farm components to form a whole-farm model capable of simulating a wide range of beef production systems. This herd submodel determined the best available feed or feed mix to meet the fiber, energy, and protein requirements for each of up to six animal groups on the farm. The groups comprised any combination of cows, nursing calves, young heifers, yearling heifers, stockers, and finishing cattle. Protein, energy, and mineral requirements were determined for each group using the Cornell Net Carbohydrate and Protein System, Level 1. Diets were formulated to meet these requirements with available feeds, and the resulting feed intake, growth, and manure DM and nutrient (N, P, and K) excretions were predicted. Required feed characteristics included CP, ruminally degradable protein, acid detergent insoluble protein, NDF, P, and K concentrations. Feed intake was predicted by considering energy intake, potentially limited by fill, and exceeding a minimum roughage requirement. Fill and roughage limits were functions of feed NDF concentrations adjusted to consider particle size distribution and the relative rate of ruminal digestibility or the physical effectiveness of the fiber. The herd submodel was verified to predict feed intakes, nutrient requirements, diets, and manure excretions similar to those recommended or measured for beef animals. Incorporation of the beef herd submodel with other farm components, including crop growth (alfalfa, grass, corn, small grain, and soybean), harvest, storage, feeding, grazing, and manure handling, provided the Integrated Farm System Model. This comprehensive farm-simulation model is a useful research and teaching tool for evaluating and comparing the long-term performance, economics, and environmental impact of beef, dairy, and crop production systems.

Reduction of nitrogen loss in animal production requires whole-farm management. Reduced loss from one farm component is easily negated in another if all components are not equally well managed. Animal excretion of manure N can be decreased by improving the balance of protein or amino acids fed to that required by individual animals or animal groups or by improving production efficiency. Management to increase milk, meat, or egg production normally improves efficiency by reducing the maintenance protein required per unit of production. Large losses of manure nitrogen occur through the ammonia and nitrous oxide that are emitted into the atmosphere and the nitrate leached into groundwater. Up to half of the excreted nitrogen is lost from the housing facility, but this loss can be decreased through frequent manure removal and by avoiding deep litter systems and feedlots. Techniques such as acid treatment of manure, scrubbing of ventilation air, and floor designs for separating feces and urine substantially reduce ammonia emissions, but these practices are often impractical or uneconomical for general use. Manure storage units improve nutrient utilization by allowing better timing of nutrient application with crop needs. At least 70% of the nitrogen entering anaerobic lagoons is typically lost, but a less than 10% loss can be maintained using slurry storage with a natural crust or other cover, or by drying poultry manure to at least 50% dry matter. Irrigation and surface spreading of manure without soil incorporation often ensures the loss of all remaining nonorganic nitrogen (typically, 20 to 40% of remaining nitrogen). Rapid incorporation and shallow injection methods decrease this loss by at least 50%, and deep injection into the soil essentially eliminates this loss. For grazing animals, excessive loss can be avoided by not overstocking pastures and avoiding late fall and winter grazing. Reducing emissions between the animal and the soil can lead to greater leaching and denitrification losses from the soil if this additional nitrogen is not used properly. The use of a crop rotation that efficiently absorbs these nutrients and applying nitrogen near the time it is needed by crops reduce the potential for further loss. Maintaining the proper number of animals per unit of land available for manure application is always crucial for efficient recycling of nitrogen. Our understanding of nitrogen loss processes is improved through modeling, and computer models assist in the development of integrated systems for efficient and economical nitrogen use in animal production.

Automatic milking systems (AMS) offer relief from the demanding routine of milking. Although many AMS are in use in Europe and a few are used in the United States, the potential benefit for American farms is uncertain. A farm-simulation model was used to determine the long-term, whole-farm effect of implementing AMS on farm sizes of 30 to 270 cows. Highest farm net return to management and unpaid factors was when AMS were used at maximal milking capacity. Adding stalls to increase milking frequency and possibly increase production generally did not improve net return. Compared with new traditional milking systems, the greatest potential economic benefit was a single-stall AMS on a farm size of 60 cows at a moderate milk production level (8600 kg/cow). On other farm sizes using single-stall type robotic units, losses in annual net return of 0 dollars to 300 dollars/cow were projected, with the greatest losses on larger farms and at high milk production (10,900 kg/cow). Systems with one robot serving multiple stalls provided a greater net return than single-stall systems, and this net return was competitive with traditional parlors for 50- to 130-cow farm sizes. The potential benefit of AMS was improved by 100 dollars/cow per year if the AMS increased production an additional 5%. A 20% reduction in initial equipment cost or doubling milking labor cost also improved annual net return of an AMS by up to 100 dollars/cow. Annual net return was reduced by 110 dollars/cow, though, if the economic life of the AMS was reduced by 3 yr for a more rapid depreciation than that normally used with traditional milking systems. Thus, under current assumptions, the economic return for an AMS was similar to that of new parlor systems on smaller farms when the milking capacity of the AMS was well matched to herd size and milk production level.

Long-term accumulation of soil phosphorus (P) is becoming a concern on some watersheds heavily populated with animal feeding facilities, including dairy farms. Management changes in crop production and feeding may help reduce the accumulation of excess P, but farm profitability must be maintained or improved to assure adoption of such changes. Whole-farm simulation was used to evaluate the long-term effects of changes in feeding, cropping, and other production strategies on P loading and the economics of 100-cow and 800-cow dairy farms in southeastern New York. Simulated farms maintained a long-term P balance if the following occurred: 1) animals were fed to meet recommended minimum amounts of dietary P, 2) the cropping strategy and land base supplied all of the forage needed, 3) all animals were fed a high forage diet, and 4) replacement heifers were produced on the farm to utilize more forage. The most easily implemented change was to reduce the supplemental mineral P fed to that required to meet current NRC recommended amounts, and this provided an annual increase in farm profit of about $22/cow. Intensifying the use of grassland and improving grazing practices increased profit along with a small reduction in excess P. Conversion from dairy production to heifer raising or expansion from 100 cows to a 250-cow "state-of-the-art" confinement facility (with a 70% increase in land area) were also profitable options. These options provided a long-term P balance for the farm as long as the production and use of forage was maximized and minimum dietary P amounts were those recommended by the NRC. Thus, management changes can be made to prevent the long-term accumulation of soil P on dairy farms while improving farm profitability.

Low-cost, pasture-based forage systems are a viable management alternative for small to moderately sized dairy farms in the Northeast United States. A whole farm analysis was conducted to evaluate the potential long-term environmental impact and economic benefit of varying the level of concentrate supplementation on seasonal grazing dairies. A representative dairy farm was simulated with various production strategies over 25 yr of historical Pennsylvania weather using the Dairy Forage System Model. A representative grazing farm (81 ha) was simulated with four levels of daily concentrate supplementation: 1) no supplement, 2) 3 kg of DM/cow in early lactation, 3) 6 kg of DM/cow in early lactation, and 4) 9 kg of DM/cow in early lactation fed daily to the lactating cows to meet annual milk production levels of 5000, 6068, 6968, and 7700 kg/cow, respectively. These farm systems were then compared to an alfalfa- and corn-based confinement system on the same land base where total mixed rations were fed to maintain an annual milk production level of 9000 kg/cow. The five systems were simulated for three scenarios. In the first, total milk sold per farm (625,000 kg) was similar across all systems. In the second, cow numbers were held constant across all systems (100 mature cows), and total milk sold per farm varied. In the third, stocking rate was set so that forage consumed equaled forage production on the farm. Profitability increased as supplementation level increased in the grazing systems, but at a decreasing rate with each successive level of supplementation. At higher levels of supplementation, the grazing dairy farms showed greater profitability than the confinement systems. Economic risk or year-to-year variation also decreased as concentrate supplementation level increased. The grazing systems showed an environmental benefit compared with the confinement systems by decreasing nitrogen leaching losses. Concentrate supplementation of grazing lactating dairy cows provided an increase in profitability and a mixed impact on nutrient balance of the farm.

A dairy herd submodel was created for integration with other farm submodels to form DAFOSYM, a dairy farm simulation model. The herd submodel determines the best mix of available feeds to meet the fiber, energy, and protein requirements for each of six animal groups. The groups are early-, mid-, late-, and nonlactating cows, heifers over 1 yr old, and younger heifers. Feed intake, milk production, and manure dry matter and nutrient (N, P, and K) excretions are functions of the nutrient content of the diets. Required feed characteristics include crude protein, rumen degradable protein, acid detergent insoluble protein, net energy of lactation, neutral detergent fiber, total digestible nutrients, P, and K concentrations. Feed intake is predicted with fill and roughage units. These units are functions of feed neutral detergent fiber adjusted for particle size distribution and the relative rate of ruminal digestibility or physical effectiveness of the fiber. The herd submodel predicted feed intakes, nutrient requirements, diets, and manure excretions similar to those recommended or measured for dairy animals. When integrated with other farm components in DAFOSYM, the comprehensive model provides a useful tool for evaluating the long-term performance and economics of alternative dairy farm systems.

On a typical dairy farm today, large amounts of N are imported as feed supplements and fertilizer. If this N is not recycled through crop growth, it can lead to large losses to the atmosphere and ground water. More efficient use of protein feed supplements can potentially reduce the import of N in feeds, excretion of N in manure, and losses to the environment. A simulation study with a dairy farm model (DAFOSYM) illustrated that more efficient feeding and use of protein supplements increased farm profit and reduced N loss from the farm. Compared to soybean meal as the sole protein supplement, use of soybean meal along with a less rumen degradable protein feed reduced volatile N loss by 13 to 34 kg/ha of cropland with a small reduction in N leaching loss (about 1 kg/ha). Using the more expensive but less degradable protein supplement along with soybean meal improved net return by $46 to $69/cow per year, dependent on other management strategies of the farm. Environmental and economic benefits from more efficient supplementation of protein were generally greater with more animals per unit of land, higher milk production, more sandy soils, or a daily manure hauling strategy. Relatively less benefit was obtained when either alfalfa or corn silage was the sole forage on the farm or when relatively high amounts of forage were used in animal rations.

Eighty-nine samples, 45 of standing forage and 44 of baled hay, were collected from alfalfa harvested at various maturities over three cuttings each during 2 yr. Alfalfa was cut and conditioned mechanically; samples of standing forage were collected by removing bunches of forage from windrows and freeze-drying them. Forage was allowed to field cure and was harvested at an average 80% DM as small rectangular bales; samples of baled hay were collected by coring bales after storing for 3 to 6 mo. Samples were analyzed for DM, ADF, total N, fractions of total N present as ADIN, N degraded at 0 h, and potentially degradable protein N. Ruminal protein degradation rates and escapes were estimated using an inhibitor in vitro system, assuming that ADIN was unavailable and that ruminal passage rate was .06/h. Standing forage contained smaller fractions of ADIN and N degraded at 0 h, contained a larger fraction of potentially degradable N, and had more rapid degradation rates and lower estimated protein escapes than baled hay. Mean degradation rates and estimated escapes were .171/h and 24% for standing forage and .075/h and 40% for baled hay. There were no differences in degradation rate or estimated escape because of harvest year, and neither was significantly related to maturity or to ADF concentration. Results indicate a significant advantage in ruminal protein escape, compared with grazed alfalfa, for alfalfa harvested and stored as hay.