An assessment of the environmental sustainability of beef production in Canada

Abstract This study assessed the environmental impacts of beef cattle production and their effects on the overall sustainability of Canadian beef production. Cradle to farm gate, cradle to processor’s gate, and cradle to consumer plate life cycle assessments were carried out to quantify greenhouse gases (GHG), resource use (i.e., water, land, and fuel), and potential water and air pollution (i.e., freshwater eutrophication, terrestrial acidification, and photochemical oxidants formation). Across the production chain, feed production had the greatest impact on most environmental indicators. The GHG intensity without dairy meat was estimated as 10.4 kg CO2-eq per kg of live weight (LW), corresponding to 32.8 kg CO2-eq per kg of consumed boneless beef. Including dairy meat reduced GHG intensity by 5.8% (0.6 kg CO2-eq kg LW–1) compared to when it was excluded. Other environmental metrics per kg of LW were 657 L, 38.7 m2 annual crop-eq, 0.4 kg oil-eq, 2.6 kg P-eq, 115.9 kg SO2-eq, and 8.7 kg NOx-eq for water use, land use, fossil fuel use, freshwater eutrophication, terrestrial acidification, and photochemical oxidants, respectively. Data provide benchmarks for use in future regional and national assessments that are designed to encourage the adoption of sustainable management practices that can lower the environmental footprint of Canadian beef production.


Introduction
The growing global demand for sustainable and responsible animal protein production, while simultaneously decreasing the negative environmental impacts of this sector, is a significant challenge for animal agriculture.Livestock have been deemed to be responsible for the use of 32.0% of the world's freshwater, and 30.0% of the global arable land (Herrero et al. 2013), while producing 14.5% of the global greenhouse gas (GHG) emissions (Gerber et al. 2013).The cattle industry has been considered the least environmentally sustainable among the livestock sectors, as it has been estimated to account for 61.7% of the global livestock sector's GHG emissions (Food and Agriculture Organizations 2022).In Canada, the beef industry is also one of the main pillars of agriculture, generating an annual output of almost CAD$10.2 billion in farm sales (Statistics Canada 2022a).Canada is the eighth largest beef-exporting country with exports to more than 50 countries at a value of CAD$4.5 billion in 2021 (Canadian Meat Council 2022; United States Department of Agriculture 2022).The market for beef is continuously evolving, and the entire value chain of the Canadian beef industry is seeking to adopt environmentally sound and responsible practices to meet the expectations of both producers and consumers.Therefore, the beef sector in Canada must continue to grow public trust through multi-stakeholder engagement and the use of science-based approaches to measure its progress in addressing sustainability issues.Although advances have been made regarding the assessment of GHG emissions of the Canadian beef value chain, the impacts of beef production on ecosystem services, such as water and air quality have been less studied (Legesse et al. 2016(Legesse et al. , 2018;;Pogue et al. 2018).In the United States, several comprehensive methodologies have been developed to characterize beef production systems and evaluate their environmental sustainability (Asem-Hiablie et al. 2019;Rotz et al. 2019;Putman et al. 2023).Similarly, benchmarking production practices and environmental impacts associated with the beef industry using comprehensive life cycle assessment (LCA) methods is critical to identifying and prioritizing best management practices that can contribute to the sustainability of Canadian beef production.
The Canadian Roundtable for Sustainable Beef (CRSB) under the National Beef Sustainability Assessment (NBSA) initiated a nationwide LCA using data collected in 2014 (CRSB 2016).This initiative provided the first opportunity to examine the environmental, social, and economic sustainability of the Canadian beef industry, and to establish benchmarks and identify areas for improvement.Thus, the present study aimed to quantify current environmental metrics associated with the Canadian beef sector using 2021 production data, while highlighting and discussing areas that have realized marked improvement since 2014, as well as those in which further improvements are needed.

Methodology
This LCA was conducted using the International Organization for Standardization (ISO 2020a(ISO , 2020b) ) approach, following ISO14040 and ISO14044 standard requirements.Environmental impacts were assessed using the following indicators: GHG emissions, fossil energy use, blue water use (irrigation and direct animal water intake), land use, freshwater eutrophication, terrestrial acidification, and photochemical oxidant formation.

Scope and functional unit
The scope of the present study was a value-chain analysis, covering pre-farm gate (fertilizer and herbicide production), farm gate (cow-calf, backgrounding, and finishing operations and feed production), and post-farm gates (slaughterhouses and packers, processors, retailers, and consumers) of the Canadian beef supply chain.
The functional units in which all impacts were calculated and reported across the LCA of the Canadian beef production systems were 1 kg live weight (LW), 1 kg carcass weight (CW), and 1 kg boneless beef (BB).An additional functional unit was added to assess the environmental footprint through to consumer, i.e., 1 kg of consumed BB (CB; 100 g serving size).

System boundaries
The system boundaries of the LCA are shown in Fig. 1 and include emissions from cattle production, slaughter and primary packaging, secondary packaging and processing, retail and consumption, as well as other inputs including transportation and the upstream production of resources such as fertilizer and herbicides.Meat from the dairy cattle industry (i.e., cull cows, steers, and heifers) was also included in the assessment of the carbon footprint of Canadian cattle production.Purchased feed and feed production on the farm considered all inputs (i.e., seeds, fertilizer, and pesticides).Other resource inputs included energy (i.e., electricity, natural gas, and diesel), water, machinery, and buildings.Secondary packaging and processing required for retail beef and associated products directly purchased by consumers were also included.However, additional meat processing, where raw beef was further processed into other final products (e.g., bolognese sauce, sausage, and lasagna), was excluded.Impacts that contributed <1% to the overall value chain, such as feed additives or supplements, veterinary medicines, and the footprint associated with the administrative aspects of beef production such as record keeping, were also excluded.

Data sources and modeling procedures
Data sources, as summarised in the supplementary information, included primary and secondary data.The primary data consisted of survey information from Canadian beef producers or the previous CRSB assessment (CRSB 2016).When primary data were not available, secondary data were obtained from the literature, expert opinion, life cycle inventory tools (i.e., Ecoinvent v3.7; Agri-footprint 5.0), and Canadian government databases (i.e., Statistics Canada).Data collected in 2021 included cattle and feed production, resource use (i.e., water, land, and energy) and emissions from the packaging, processing, retail, and consumer sectors.As a result of differences in climate, culture, and available resources, cattle production systems in both western and eastern Canada were considered.

Cattle production
The beef industry in Canada is diverse in terms of the type and number of cattle per operation and feeding and management practices employed (Sheppard et al. 2015).Beef production in Canada typically involves three production stages: cow-calf (cows and calves), backgrounding (weaned calves fed primarily forage-based diets), and finishing (steers and heifers fed high-energy grain-based diets), after which point cattle are sent for slaughter (Aboagye et al. 2021).Canadian beef production was broadly divided into two systems based on the management practices used to bring calves to slaughter: (1) calf-fed system: heavier calves (∼261 kg) were weaned and placed immediately on a finishing diet (i.e., cow-calf and finishing phases) and (2) yearling-fed system: lightweight weaned calves (∼227 kg) were backgrounded on pasture and overwintered in the feedlot (backgrounders) and then grassfed as yearlings before finishing (cow-calf, backgrounding, and finishing phases).These management practices represent the two extreme scenarios between intensive and extensive feedlot management practices in Canada (CRSB 2016).The calf-fed and yearling-fed production systems were assumed to account for 45.0% and 55.0% of Canadian beef cattle production in 2021, respectively (Brenna Grant, Canfax Research Services, personal communication, 2022).
The major cattle categories included in the analysis were cows, as well as heifers and steers that were backgrounded and finished.The required population and production parameters for the model, such as cattle inventory, body weight at different stages of production (birth, weaning, backgrounding, finishing, and slaughter), dry matter intake (DMI), the number of days on feed, average daily gain, and CW were determined based on the census data (Government of Canada 2021;Statistics Canada 2022b), expert opinion (CRSB, personal communication), and Canadian literature (Mu et al. 2016;Bourgon et al. 2018;Lafreniere et al. 2020; Tables 1  and 2).LW (slaughtered weight marketed) was the total of finished steers and heifers and cull cow weights produced by each system.Cull cow LW was determined using a 13.0% culling rate (Canfax 2021).LWs for the east and the west were also obtained for finished heifers and steers and cows, by dividing the CW of steers, heifers, and cows (Government of Canada 2021) by their corresponding dressing percentage (59.0%,57.0%, and 50.0%, respectively; Agricultural Marketing Guide 2021).The number of cattle in each category could not be garnered from Statistics Canada data; hence a scale factor or cohort multiplier methodology was employed as per the 2016 CRSB assessment (CRSB 2016; Table 1).The multiplier provided a ratio value of each cattle type relative to the others in the cohort system by estimating the number of animals of each category required to produce one finishing animal and with the assumption of a 13.0% culling rate for cows.It was assumed that the ratio of heifers to bulls at birth was 50:50, while the proportion of heifers and steers at the backgrounding and yearling phase was 25.0% for each of the subcategories.The scale factor for each cattle type was then calculated as the quotient between the ratio of each cattle category or subcategory and the difference resulting from subtracting the culling rate, heifer replacement rates, or mor- a These data show the current production system (i.e., 2021), with calf-fed and yearling-fed production systems accounting for 45% and 55% of the Canadian beef cattle production, which differ from the 2014 (41%: 59%) production year ( CRSB 2016), respectively.b DMI, dry matter intake c Cattle on feed at the cow-calf phase were calves fed preconditioned diets post-weaning or growing cattle fed in confinement at the backgrounding phase.All cattle were finished in confinement.d Western production system includes the production systems in Alberta, British Columbia, Manitoba, and Saskatchewan, while Eastern production includes Ontario, Quebec, and the Atlantic provinces.
tality rates of the production system from 1 (e.g., for the calf category; 1/(1 − mortality rate) = 1/(1 − 3.3%) = 1.034).The mortality rates for the cattle categories ranged from 0.86% to 3.3%, and the heifer replacement rates ranged from 12.0% to 15.0% (Canfax 2021).By multiplying the scale factors by the total slaughter number (Statistics Canada 2022b), the number of animals slaughtered in each cattle category was obtained for the production year (Table 2) to quantify the overall annual impact of the total Canadian cattle cohort.
Generally, the impact of transportation on the footprint of beef cattle systems in North America is relatively small, even when cattle are transported over long distances (Rotz et al. 2015).However, to be consistent with the 2016 CRSB assessment, the transportation of cattle within the production systems was considered in the LCA.The average distance covered for transporting calves from one stage of the production system to the other and from the finishing stage to the packing plant was assumed to be 300 km (AARD 2010).

Feed production
The amount of feed produced and purchased was estimated based on the amount of feed consumed (i.e., DMI), field and feeding losses, and the number of days on feed and pasture standardized for the various cattle groups (Table 1).A cow-calf cost of production survey (COP network) was con-ducted using 2020 data, with 115 cow-calf producers creating nine benchmark farms in the east (Atlantic, Ontario, and Québec) and 16 benchmark farms in the west (Alberta, British Columbia, Manitoba, and Saskatchewan) (Canfax 2021).The producers in this COP network were grouped primarily based on winter feed ingredients, and calving and weaning dates (Canfax 2021).Rations for cows, bulls, and calves were based on those reported in the COP network survey and weighted by information in the Farm Management Survey (FMS; Canfax 2017) to generate a weighted average of the typical rations used in each province.For example, in Ontario, corn silage accounted for 10.0% of the average forage-based ration for cows, while hay and other ingredients accounted for 51.0% and 39.0%, respectively (Canfax 2017).Cows were assumed to be maintained over the winter through the consumption of preserved forages, including hay or silage in confinement, or grazed annuals (e.g., standing cover crops, swath gazing, and corn grazing) in both eastern and western Canada.Cows were assumed to be fed in confinement for 102 and 75 days and on pasture for 263 and 290 days in eastern and western Canada, respectively.Feed requirements for breeding bulls were excluded from the model, as their consumption was considered negligible.
Preconditioning of calves before sale is a practice that is becoming increasingly common in the Canadian cow-calf sector.With this management practice, weaned calves are retained at the site of production for a period of time which varies regionally and with marketing practices (BRCR 2019).Cow-calf producers typically wean calves at 4 to 7 months of age (BCRC 2019).Based on a Western Canada and Atlantic Canada cow-calf survey, 22.0% of cow-calf producers in western Canada and 36.0% in eastern Canada preconditioned calves for 17 and 34 days, respectively (BCRC 2019;Canfax 2021).
Feed requirements of backgrounding and finishing cattle were determined based on expert opinion (e.g., Gowans Feed Consulting in the west, and Ontario Ministry of Agriculture, Food and Rural Affairs in the east), with consideration of the initial and final body weights, feeding season, and regional differences in diets.Feed sources included hay, straw, barley silage, corn silage, and grass silages as forages and highenergy feeds, including barley, corn, wheat, oats, screening pellets, soybean meal, and dried distiller's grain with solubles.The diets in the east were corn-based with corn silage and grain components accounting for 38.6% and 16.5% of dietary ingredients in backgrounding diets or 13.4% and 63.8% (DM basis) in finishing diets, respectively.The rations in the west were barley-based, with barley silage: grain portions of 22.0:63.8 in backgrounding and 8.5:71.4 in finishing diets.Diets were formulated to meet or exceed the nutrient requirements of each of the specific categories of cattle (NRC 2000; Tables S1-S3).
Losses occurring during field harvest and preservation were assumed to be 12.0% for silages and hay and 3.0% for grains, while feed wastage was estimated to be 5.0% for silage, 20.0% for hay, and negligible for grain (Legesse et al. 2016).Barley straw was used as bedding for cattle in confinement (CRSB 2016).Transportation of purchased feed was also considered.The average transportation distance assumed for purchased feeds to farms was 15 km (AARD 2010).Feed imports were excluded as Canadian beef producers purchase most feed locally.

Harvesting, retail, and consumer stages
The harvesting stage of the value chain included the transport and slaughtering of live cattle, processing of the carcass into BB, and packaging for shipment to the retailer and consumer.Input data to estimate the environmental footprint associated with this practice were sourced from interviews with processors and retailers, as well as from life cycle inventory databases (Ecoinvent v3.7).Canadian processors representing approximately 86% of slaughter cattle participated in the interviews (CRSB 2016).The analyses considered primary, secondary, and tertiary packaging obtained from predefined profiles in Ecoinvent v3.7.Plastics and other waste materials associated with packaging were assumed to meet average recycling and landfilling rates in the east and west (PACNEXT 2014;ECCC 2022).This resulted in estimates for each kilogram of BB produced of 61.0% and 39.0% for plastics and 29.0% and 71.0% for paper and board packaging being recycled and landfilled, respectively.Food waste and losses from the farm gate to the consumer were also considered.It was assumed that 4.2% was lost during transport and handling, with a weighted average dressing percentage (carcass yield) of 58.5% for finishing cattle and cull cows (CRSB 2016).Assumed losses from carcass to boneless meat were 29.5%, retail losses were 4.3%, and consumer losses were 10.7% (CRSB 2016).These estimates were used to calculate the LW needed to produce 1 kg of consumed BB (CRSB 2016).

Environmental impact metrics
Consistent with the CRSB (2016) assessment, a cohort multiplier was used for each stage of production to estimate the overall footprint of beef production.For example, for cattle on feed, the cohort multiplier was multiplied by the ratio of days on feed to total days to finish and then the daily emissions or impacts from the consumption of the specific diets fed to cattle at each stage of production.A similar process was followed for manure-related impacts, daily water use, and land use.This generated a daily equivalent environmental impact for each animal category and by using the cohort multiplier and the production days, overall impacts over the life cycle of cattle from birth to slaughter were generated.Since the LW produced by each system was the total of a finished animal (steers and heifers) plus cull-cow weights, to generate the impact per kg LW, the sum of impacts from each animal category was divided by the total LW within each cohort.When determining the average environmental impacts of each region and at a national level, values were weighted in proportion to their contribution to the total cattle produced.The national value was based on 84% of production occurring in the west and 16% in the east (Statistics Canada 2022b).
Further, an economic allocation was also used to distribute the environmental impacts between meat and co-products (e.g., blood, hide, fats, hooves, etc.).For instance, for CW, 95.0% and 5.0% of the impacts were allocated to meat and co-products, respectively (CRSB 2016).While for BB, 90.0% and 10.0% were allocated to meat and co-products, respectively (CRSB 2016).An economic allocation was also used to allocate impacts between different co-products of feed production, such as canola meal and dried corn distillers' grain.Because of their variable costs and the small contribution of these by-products (less than 5.0% of total feed) to the total amount of feed consumed, the default economic allocation model in Ecoinvent was used.The life cycle impact assessment followed the methodology of the Intergovernmental Panel on Climate Change (IPCC 2021) and ReCiPe 2016 Midpoint (H) 1.06 (Huijbregts et al. 2017) using SimaPro software (version 9.3.0.3; simapro.com).

Greenhouse gas emissions
Following the IPCC guidelines for National GHG Inventories, Tier 2 methodology, GHG emissions were estimated using secondary data from Holos (version 3.0.6;Little et al. 2008), Agri-footprint 5, and Ecoinvent v3.8 databases.Holos is based on Canadian production systems and climatic conditions and has been recently used to predict emissions from cattle production systems in Canada (Aboagye et al. 2022;Boonstra et al. 2023).Agri-footprint and Ecoinvent are repositories that cover a diverse range of agricultural processes at global and regional levels in cattle production systems in Europe (Rota Graziosi et al. 2022), Brazil (Carvalho et al. 2022), and the USA (Asem-Hiablie et al. 2019;Henderson et al. 2023;Putman et al. 2023).In the present study, the Holos database was used to estimate emissions from the cattle categories, while Ecoinvent and Agri-footprint databases were used to estimate emissions associated with crop production and off-farm processes based on Canadian practices (Tables S1  to S7).These included methane (CH 4 ) from enteric fermentation and manure on pasture or during storage (manure management system), nitrous oxide (N 2 O) from direct and indirect sources [nitrogen (N) leaching, runoff, and volatilization], and carbon dioxide (CO 2 ) from energy use.Emissions associated with the production and use of fertilizers and herbicides were based on default values in Ecoinvent (Table S4).Further, emissions associated with the transportation of cattle from one production system to another and to the processing plant were considered.Dietary ingredients with minor contributions (<1% by mass) to feed rations, such as mineral supplements, were not considered as their impacts were minimal (Asem-Hiablie et al. 2019).Carbon stocks in grasslands and perennial forages were assumed to be near equilibrium and were excluded from the analysis.The major GHG emissions, including CO 2 , CH 4 , and N 2 O, were converted to CO 2 equivalents (CO 2 -eq) based on the latest global warming potentials (GWP-100) in the sixth assessment reports (AR) of the IPCC (CO 2 = 1, CH 4 = 28, and N 2 O = 273; Smith et al. 2021).
Methane emissions arising from enteric fermentation from each cattle category were estimated based on gross energy intake (IPCC 2019) and CH 4 conversion factors (Y m ; Anele et al. 2014; Holos database; Table S1 to S3).To account for CH 4 emissions from manure management, the amount of volatile solids (VS) produced were estimated based on gross energy intake and feed digestibility (IPCC 2019; Table S5).Finally, manure CH 4 emissions were estimated by calculating the product of the VS, the maximum CH 4 -producing capacity (B o ; 0.19 m 3 CH 4 kg VS −1 ), CH 4 conversion factor (MCF), and density (0.67 kg m −3 ).The MCF for manure was dependent on the manure management system employed (Table S5).
In addition to CH 4 , direct N 2 O emissions from soil and cropping including from above-and below-ground crop residue decomposition and manure and synthetic fertilizer application were estimated, as were indirect N 2 O emissions including emissions from volatilization, leaching, and runoff.Direct N 2 O emissions from manure were quantified using the emission factors (EF; kg N 2 O-N kg manure N −1 ) in Holos (Little et al. 2008), and the N excretion rate (kg N head −1 day −1 ).Nitrogen excretion rate of manure (urine and feces) was estimated using DMI, and dietary CP content based on the equation described by Dong et al. (2014).Indirect N 2 O emissions from N volatilization, leaching, and run-off were estimated using the N excretion rate (kg N head −1 day −1 ), EF from IPCC (2019), and the portion of N lost from fertilizer, manure, and residues in Holos (Little et al. 2008; Table S5).The portion of N that was lost through leaching in pastures was also estimated for pasture and was assumed to be 21.5% and 39.3% in western and eastern Canada, respectively (CGIAR-CSI 2015).
In the previous assessment (CRSB 2016), the dairy sector was excluded to be consistent with previous national-scale beef inventories.However, in the present study, the GHG emissions associated with beef produced from dairy cattle including steers, heifers, and cows were also estimated and benchmarked against 2014 data based on the proportion of beef from dairy breeds relative to beef from traditional beef breeds.In western Canada, beef accounted for 98.2% and 94.2% and dairy accounted for 1.8% and 5.8% of the meat produced in 2014 and 2021, respectively (Brenna Grant, Canfax Research Services, personal communication, 2022).In eastern Canada, beef accounted for 68.7% and 70.4% and dairy accounted for 31.3% and 29.6% of the meat produced in 2014 and 2021, respectively (Brenna Grant, Canfax Research Services, personal communication, 2022).Nationally, in 2014 and 2021, 17.9% and 17.2% of the beef produced in Canada came from dairy animals, while 82.1% and 82.8% were from traditional beef sources, respectively (Brenna Grant, Canfax Research Services, personal communication, 2022).Dairy breeds raised as beef in Canada are usually imported from the USA to western Canadian feedlots.Thus, transporting dairy cattle from the USA to western Canada was estimated at 1200 km between the dairies located in the western USA and feedlots in southern Alberta.Greenhouse gas emissions related to meat production from dairy cattle were allocated as per the International Dairy Federation methodology (IDF 2015).Allocation of emissions to meat from dairy was per an LCA conducted by Dairy Farmers of Canada (DFC 2018), using system boundaries similar to those used in the present study.The values allocated from dairy for meat were 6.0, 6.7, and 6.5 kg CO 2 -eq kg of LW −1 at the west, east, and national levels, respectively.A weighted average using the proportions of the carbon footprint of meat from dairy and traditional beef was allocated to determine the overall carbon footprint of beef produced when both traditional beef and dairy production systems were considered.This procedure was repeated at regional (west and east) and national levels.A separate analysis was conducted for the traditional beef breeds, with or without dairy breeds using the GWP-100 coefficients in the fifth AR (AR5; CO 2 = 1, CH 4 = 28, and N 2 O = 265; Myhre et al. 2013), so as to be consistent with the carbon footprint values reported by DFC (2018).

Water, land, and fossil fuel use
Water use (L per functional unit) was calculated following the ISO 14046 guidelines on water footprint (ISO 2014).Only blue water, which includes water used for irrigation and direct consumption and cleaning, was considered.Irrigation intensities (m 3 ha −1 ) were modified to reflect practices specific to western and eastern Canada (Statistics Canada 2021a, 2021b).Thus, the irrigation intensity and the proportion of total land used for beef production that was irrigated were 2800 m 3 ha −1 and 3.1%, 3100 m 3 ha −1 and 3.4%, and 2800 m 3 ha −1 and 1.7% for field crops, hay, and tame pasture, respectively.The product of the irrigation intensity and proportion of irrigated area for beef production was the average irrigation in m 3 ha −1 for each crop.Average irrigation intensities were used to estimate the indirect water requirements for irrigation based on the quantity of feed consumed by each cattle category.Daily water use including drinking and cleaning was estimated based on animal category (AARD 2010; CRSB 2016).Data on water use for processing beef were also sourced through interviews with processors and used to estimate the water needed to process 1 kg CW and 1 kg of BB.
Land use was quantified according to the ReCiPe Midpoint (H) 1.06 model ( 2016) in m 2 a crop-eq per functional unit (where a = annual), with consideration for loss of habitat and soil disturbance due to land occupation and conversion for agricultural purposes.The total land area required to produce feed was estimated based on crop yields, DMI, dietary composition, and field and feeding losses.Further, the land area associated with grazing was obtained from the previous assessment (CRSB 2016) and was deemed to not have changed significantly since that time.The land occupied by grazing cattle was 57.0 m 2 head −1 day −1 , while for cattle in confinement, this was set at 0.6 m 2 head −1 day −1 (CRSB 2016).The land occupation flows of the Ecoinvent databases with the same time reference were updated with the area used for beef production for each land use type.The midpoint characterization factors (CF) were then applied to these calculated areas to estimate land use.For annual crops, (i.e., any land used for production of feed), a CF of 1 was applied, while for grazing land a CF of 0.55 was applied (Huijbregts et al. 2017).
Fossil fuel use including the extraction of coal, oil, and natural gas used for heating, transportation, and electricity generation were estimated across the beef value chain in terms of kg of oil-eq.The energy use across the beef supply chain was based on composition (Agri-Footprint 5) and consumption (Ecoinvent v3.8; CRSB 2016; Table S6).Energy consumption on-farm (unit head −1 day −1 ) was sourced from the previous assessment (CRSB 2016).Similarly, estimates of energy use intensity (kWh kg BB −1 ) with refrigerant gases and leaks (kg refrigerant kg BB −1 ) during the packaging and retail stages were obtained from the previous assessment (CRSB 2016).However, at the consumer level, energy use values for storage and cooking (kWh kg BB −1 ) were obtained from Natural Resources Canada's Office of Energy Efficiency (2012; Table S6).

Water, land, and air pollution
Water pollution was based on freshwater eutrophication.Eutrophication results from the release of phosphorus (P) from fertilizer and manure into aquatic ecosystems, and was expressed in P equivalents (g P-eq).The model estimated phosphate (PO 4 3− ) losses from pasture by considering P runoff with surface water, during soil erosion and leaching into groundwater (Prasuhn 2006).The models for sources of PO 4 3 loss account for P in the diet, but due to limited data, the PO 4 3− leaching rate (g of PO 4 3− head −1 day −1 ) from Hofmann and Beaulieu (2006) was assumed for all cattle categories (Table S7).
Land pollution based on terrestrial acidification was estimated as the change in soil acidity due to increases in ammonia (NH 3 ), nitrous oxides (NO x ), and sulfur dioxide (SO 2 ) emissions and expressed as g SO 2 -eq.Ammonia emissions associated with the various manure management systems including deep bedding, solid storage, composting, and pasture were estimated as described by Chai et al. (2014;Table S7).NO x emissions during manure storage were assumed to be at a rate of 0.094 kg NO x head −1 year −1 (EMEP/EEA 2013).Emissions associated with manure applied to crops were allocated to crop production.
Air pollution estimates were based on the formation of photochemical oxidants and their toxicity to human health (damage to lungs) and terrestrial ecosystems (damage to wildlife and plant species).Photochemical oxidants form tropospheric ozone due to NO x and volatile organic compounds (VOCs) released during the combustion of fossil fuels (EMEP/EEA 2013) were expressed as g NO x -eq.

Uncertainty, sensitivity, and scenario analyses
In compliance with ISO 14044, all data sources used for this study were assessed based on time-, geographical-, and technological coverage, as well as precision, completeness, representativeness, consistency, reproducibility, source description, and information uncertainty.The pedigree matrix for rating inventory data (Weidema et al. 2013) was used as a guide to evaluate data quality and conduct a quantitative uncertainty analysis.The impacts of data on environmental indicator metrics were also examined using sensitivity testing and contribution analyses.In the framework of this LCA, data with high importance were those that had the greatest impact on multiple indicator variables.Data with moderate importance were those whose relative contribution to the potential impacts was among the highest for at least one indicator.Data with low importance were never among the highest in terms of relative contribution to the potential impacts.Processes with high and moderate importance in terms of en-vironmental impacts were all modeled using primary data, which resulted in lower data uncertainties.Primary data were as current as possible since they were collected for the most recent available years (2020 or 2021).Secondary data were used mainly for the retail and consumption phases and their reliability and representativeness were deemed to be acceptable as they were verified by measurements or assumptions, and sourced from more than 50% of locations relevant to the market.Quantitative analysis of the uncertainty due to the variability of inventory data and characterization of the impact assessment were performed using Monte Carlo simulations with 1000 iterations, or until stabilization of variability was reached.
For the sensitivity analysis, the majority of data were obtained from direct sources, such as Statistics Canada, Canadian literature on beef production, and Canfax Research Services.Generally, the same or enhanced sources from the previous assessment (CRSB 2016) were considered.However, in some cases, only expert judgement was available.Slaughter weights of cattle were calculated from the Canadian Beef Grading Agency's annual average CW based on dressing percentages (Government of Canada 2021; Government of Alberta 2022).Estimated values fell within a 10.0% range of values found in unpublished data (Brenna Grant, Canfax Research Services, and Feedlot Health Management Services, personal communication, 2022).Therefore, for sensitivity analysis, an increase and a decrease of end-weights of 10.0% at a constant production period were considered, with three scenarios assessed independently.First, some of the common practices in western Canada such as extensive winter grazing/feeding (i.e., bale, swath, or stockpiled grazing) were compared to confined winter feeding practices common in eastern Canada.Second, two production systems (calf-fed vs. yearling-fed) were considered based on western production parameters.Finally, the carbon footprint of beef with or without dairy meat was assessed.Data collected in 2014 were reanalyzed using the same model as for 2021 to enable comparison between the 2 years.

Results and discussion
The average environmental footprint intensities along the entire Canadian beef supply chain are presented for the western and eastern regions along with national impacts for the 2021 production year (Table 3).Results from 2021 were also compared to those generated 7 years earlier in 2014 (CRSB 2016).Across the current production chain, cattle and feed production on-farm typically had the greatest impact on the environmental indicators, including the carbon footprint, resource use (water, land, and fossil fuel), freshwater eutrophication, terrestrial acidification, and photochemical oxidation (Figs.2A and 2B).Levels of impact from cattle and feed production on-farm on the indicators typically exceeded 40.0% or 30.0% in the west or east, respectively, as compared to other off-farm practices including transportation, processing, packaging, retail, and consumption.In 2014, cattle and feed production accounted for more than 50.0% of the impact on all of the environmental indicators (CRSB 2016).Similarly, the life cycle impacts of Australian (Wiedemann et al. 2015) and The functional unit to which all impacts were calculated and reported across the life cycle of the Canadian beef production systems were 1 kg of live weight (LW), 1 kg carcass weight (CW), 1 kg of boneless beef (BB), and 1 kg of consumed boneless beef (CB) b West includes the weighted average for Alberta, British Columbia, Manitoba, and Saskatchewan, while east includes Ontario, and Quebec, and the Atlantic provinces.National is mean environmental footprints weighted by west and east.
USA beef (Asem-Hiablie et al. 2019;Putman et al. 2023) value chains also reported that beef and feed production accounted for more than 50.0% of the impact on these environmental indicators.

Greenhouse gas emissions
The estimated carbon footprint intensities of the current beef production systems, excluding dairy cattle, from cradle to the various gates of production are shown regionally and nationally in Table 3. Across the beef supply chain, the average GHG emission intensity was slightly greater in the west (10.5 kg CO 2 -eq kg of LW −1 ) than in the east (9.8 kg CO 2 -eq kg of LW −1 ), resulting in a weighted average of 10.4 kg CO 2 -eq kg of LW −1 in Canada at the farm gate.All functional units exhibited a similar trend in GHG emissions (Table 3).Beef cattle are commonly raised in confinement in the east compared to pasture feeding in the west (CRSB 2016).This regional difference in feeding practices resulted in a similar number of production days from birth to finish with cattle spending more time in confinement in the east and more time on pasture in the west.Cattle in confinement usually have a lower carbon footprint than pasture-fed cattle, as they usually require a shorter time to reach market weight (Pelletier et al. 2010).The regional differences in the carbon footprint were therefore characterized by variations in management practices including reduced days on pasture with an improved rate of gain (3.8% increase in the east relative to the west), coupled with a lower proportion of beef produced in the east (16.0%) than the west (84.0%).
In the present study, the national carbon footprint estimate was comparable to the previous 2014 CRSB estimate (11.4 kg CO 2 -eq kg of LW −1 ; CRSB 2016).However, updating the 2014 estimates using the latest methodology and GWP factors to benchmark the performance of the Canadian beef sector resulted in the carbon footprint of producing a kilogram of traditional beef LW in 2021 being lower than 2014 by 17.3% (10.5 vs. 12.7 kg CO 2 -eq kg of LW −1 ) in the west and 20.9% (9.8 vs. 12.4 kg CO 2 -eq kg of LW −1 ) in the east, resulting in a 17.5% reduction, nationally (10.4 vs. 12.6 kg CO 2 -eq kg of LW −1 ).A shift in the proportion of beef produced in both regions over the 7 years from 74% to 84% in the west and from 26% to 16% in the east, coupled with fewer days to raise calves from birth to finish (market weight) in both the west (45 fewer days) and the east (52 fewer days), led to a decrease in enteric CH 4 emissions as well as CH 4 emissions from manure in confinement and on pasture.Asem-Hiablie et al. ( 2019) reported a GHG emission intensity of 48.4 kg CO 2 -eq kg of CB −1 or 14.0 kg CO 2 -eq kg of LW −1 , assuming that 3.45 kg LW produced 1 kg of CB in the USA.This value is greater than the estimate in the present study, but our study used regionally specific data for feed and cattle management practices, while Asem-Hiablie et al. ( 2019) used data from a specific beef farm to model the environmental impact of beef cattle in the USA.Estimates from our study were within the range of 16.6 to 35.2 kg CO 2 -eq kg of CW −1 generated by a recent USA LCA (Rotz et al. 2019), which also used regionally specific data to develop a national estimate of 23.3 kg CO 2 -eq kg of CW −1 (Rotz et al. 2019) or 21.0 kg CO 2 -eq kg of CW −1 (Putman et al. 2023) for beef cattle.Assuming an average dressing percentage of 59.1% (Asem-Hiablie et al. 2019), this equates to 13.8 kg CO 2 -eq kg of LW −1 or 12.4 kg CO 2 -eq kg of LW −1 for the USA studies (Rotz et al. 2019;Putman et al. 2023).In our study, we used the latest GWP-100 coefficients in AR6 (Smith et al. 2021), while Rotz et al. (2019) and Putman et al. (2023) used the coefficients in AR5 (Myhre et al. 2013).
Beef cattle production in Canada is comprised of cow-calf, backgrounding, and finishing stages.To account for variation between extensive and intensive feedlot production stages, both calf-fed (cow-calf-to-finish) and yearling-fed (a combination of cow-calf, backgrounders, yearlings, and finishing) systems were investigated.Variations in production practices between the calf-fed and the yearling-fed production systems resulted in differences in the environmental footprint intensities at the farm gate.For a kilogram of beef LW produced, the yearling-fed system had a GHG emission intensity that was 31.4% greater than the calf-fed system (13.8 vs. 10.5 kg CO 2eq, data not shown).Though many factors can influence GHG emissions on-farm, the increased emission intensity with the yearling-fed system was mainly due to the longer days spent on pasture (276 days vs. 177 days) and on feed (322 days vs. 296 days), coupled with a greater proportion (55.0% vs. 45.0%) of beef cattle being assigned to the yearling-fed relative to the calf-fed production system.Given that the vast majority of calving in Canada occurs during the spring (Sheppard et al. 2015), a variety of production systems are needed to deliver cattle at market weight to processors over the entire year.Hence, it was expected that the yearling-fed production system would have greater emissions as it requires more time for steers and heifers to reach market weight.Relative to 2014 (CRSB 2016), the proportion of the beef cattle herd in 2021 that was apportioned to the yearling-fed system was 4.0% lower, with 87 fewer days (i.e., 56 fewer days on pasture plus 31 fewer days on feed) to achieve market weight, resulting in a corresponding decrease in the carbon footprint.
In the current assessment, the predominant contributors to the GHG emission intensities at the farm gate were enteric CH 4 (62.0%west, 60.0% east), feed (21.0%both west and east), and manure management (17.0%west, 19.0% east; Fig. 3).All other contributors, including transport of animals, bedding, water, and energy accounted for 1.0% or less of total GHG emissions.Climate change and its associated effects due to livestock production are largely influenced by emissions of CH 4 .Enteric CH 4 emissions result primarily from the fermentation of feed in the rumen.In the present study, the entire beef production cycle resulted in cattle spending 53 more days on pasture in the west than in the east.Increased intake of forages due to extended days on pasture can increase CH 4 emissions, contributing to slightly greater emissions in the west compared with the east.Similarly, enteric emissions, feed production, and manure emissions were the major contributors to the carbon footprint of the Canadian beef industry in 2014 (CRSB 2016).
The lower impact of beef and feed production in 2021 as compared to 2014 in Canada (Fig. 4) or the studies conducted in Australia (Wiedemann et al. 2015) and the USA (Asem-Hiablie et al. 2019) arose in part due to lower consumption of fossil fuels for transportation, processing, packaging, retail, and consumption phases, which accounted for 60.0% and Fig. 3. Environmental footprint to produce a kilogram of live weight (LW) in 2021 at the national and regional (west and east) levels.
70.0% of use in western and eastern Canada, respectively.Relative to 2014, enteric emissions in 2021 increased by 6.0% and 9.0% in the west and east, respectively.This resulted from greater DMI and finished weights (8.9% and 1.7% greater in the west and east, respectively) in 2021.Similarly, these pro-portions in 2021 differed to some extent from those reported by Basarab et al. (2012) for western Canadian beef, which ranged from 54.1% to 54.9%, 25.7% to 26.1%, and 20.2% to 20.8% of total GHG emissions for enteric CH 4 , manure, and feed production, respectively.Rotz et al. ( 2019) also estimated that approximately 56.0% of the GHG emitted at the farm gate by beef cattle in the USA arose from enteric CH 4 emissions, with the remaining emissions coming mainly from manure and feed production.In our study, a Y m value of 7.0% was used (Anele et al. 2014) instead of 6.5% for cattle fed forage-based rations, and the GWP-100 coefficients in AR6 were greater than the AR5 estimates used by Basarab et al. (2012) and Rotz et al. (2019).Furthermore, unlike the studies of Basarab et al. (2012) and Rotz et al. (2019), the present study did not consider the effects of productivity-enhancing technologies such as growth hormones, beta-agonists, and ionophores on emissions from beef production.The use of productivityenhancing technologies in beef production improves animal performance and can reduce the carbon footprint of beef production (Aboagye et al. 2021;Boonstra et al. 2023).
The Canadian dairy industry makes a significant contribution to Canadian meat production.As a result, meat from dairy cattle including cull cows, calves, steers, and heifers was also considered when estimating the carbon footprint of cattle production.In 2021, 17.2% of the meat produced in Canada originated from domestic and imported dairy cattle, with 5.8% in the west and 29.6% in the east (Brenna Grant, Canfax Research Services, personal communication, 2022).Regionally, the GHG emission intensity in 2021 in the west with dairy cattle included was comparable to estimates that only considered beef cattle (10.4 vs. 10.5 kg CO 2 -eq kg of LW −1 ), whereas in the east it decreased by 9.2% (8.9 vs. 9.8 kg CO 2 -eq kg of LW −1 ; data not shown).The proportion of meat coming from the dairy sector relative to meat from traditional beef production in the west was lower than in the east, reflecting the lower relative proportion of dairy cattle in the west.In this region, dairy cattle are usually sourced from the USA, whereas in the east dairy cattle for meat originate primarily from local producers.The longer transport distance for dairy cattle from the USA to the west added 0.0076 kg CO 2 -eq kg of LW −1 to the emissions.The inclusion of dairy cattle slightly decreased national GHG emissions per kg of LW −1 by 5.8% compared to when they were excluded (9.8 vs. 10.4 kg CO 2 -eq kg of LW −1 ).Rotz et al. ( 2019) also estimated the carbon footprint intensity of beef with (21.3 kg CO 2 -eq kg of CW −1 ) or without (23.3kg CO 2 -eq kg of CW −1 ) meat from dairy systems and reported an 8.6% decline in the carbon footprint.Beef of dairy origin usually has a significantly lower emission intensity compared to beef from traditional beef cattle, mainly because cull cows spend the majority of their life in a dairy production system where they are fed greater levels of concentrates than beef cows.Thus, most of the emissions associated with dairy production from birth, weaning, and rearing are allocated to milk production (Rotz et al. 2010;de Vries et al. 2015).The GHG emission intensities allocated to meat production from dairy breeds in the west, east, and at the national level (6.5, 6.0, and 6.7 kg CO 2 -eq kg of LW −1 , respectively; DFC 2018) were lower than the emission intensities of traditional beef breeds that ranged from 9.8 to 10.5 kg CO 2 -eq kg of LW −1 .Consequently, if a larger proportion of meat comes from dairy production, there could be opportunities to reduce the overall carbon footprint intensity of the beef industry.
In 2014, dairy breeds accounted for 17.9% of slaughtered cattle nationally, with these proportions being 1.8% in the west and 31.3% in the east (Brenna Grant, Canfax Research Services, personal communication, 2022).Comparing 2014 and 2021, the proportion of beef produced regionally from dairy was slightly greater in the west and slightly lower in the east.Benchmarking the performance of dairy inclusion over the 7 years (2014 vs. 2021; data not shown) decreased the carbon footprint intensity by 18.1% (12.7 vs. 10.4 kg CO 2eq kg of LW −1 ) in the west and 16.8% (10.7 vs. 8.9 kg CO 2 -eq kg of LW −1 ) in the east, resulting in a 14.8% reduction nationally (11.5 vs. 9.8 kg CO 2 -eq kg of LW −1 ).
The results of the present study were within the weighted averages ranging from 16.8 to 27.0 kg CO 2 -eq kg of CW −1 for USA beef (Rotz et al. 2019).A recent study in New Zealand showed that the addition of dairy calves to replace the entire beef breeding herd decreased GHG emission intensities from the beef herd by 21.6% at the farm gate (16.7 vs. 21.3kg CO 2 -eq kg of CW −1 ; i.e., 8.9 vs. 11.3 kg CO 2 -eq kg of LW −1 ; ven Selm et al. 2021).For the USA study, GHG emissions were estimated assuming that all dairy cattle were Holsteins (Rotz et al. 2019), while the New Zealand study assumed that Jersey was the principal dairy breed (ven Selm et al. 2021).In the present study, it was assumed that 90% of the dairy cattle were Holstein (DFC 2012).Some breeds of dairy cattle are considered undesirable for meat production due to their low rate of gain (Fitch et al. 1924;Hickson et al. 2015).As in the New Zealand study (van Selm et al. 2021), the present study also considered the contribution of various classes of dairy cattle used in meat production, but not as a substitute for the breeding beef cow herd.Increasing the number of dairy calves for meat, while decreasing the beef breeding herd would decrease the number of weaned beef calves available for finishing.Although the inclusion of dairy beef has some benefits, a reduction in beef from traditional beef breeds may raise future societal and environmental concerns from consumers.This is because the meat quality of dairy beef is often criticized as inferior due to their lower birth weight and average daily gain, even though some studies have shown little difference in meat quality (Bown et al. 2016).Further, the feed efficiency of dairy breeds is often lower than that of beef cattle, possibly offsetting any gains in GHG emission intensity associated with dairy beef.

Water, land, and fuel use
On-farm, blue water is consumed by cattle and used to clean handling facilities and to irrigate crops.Post-farm gate, water is required for the slaughter, processing, and packaging of beef.Both the media and the public have criticized the large volume of water that is required to produce 1 kg of beef (Aboagye et al. 2021).The quantity of water required to produce a kg of beef LW or serve a kg of BB to a consumer differed between the two regions, averaging 761 L or 2192 L in the west and 89.9 L or 433 L in the east, respectively (Table 3).The majority of the water consumed in both regions for cattle production was associated with feed production with about 99.0% of this used for irrigation (Fig. 3).The greater water footprint (672 more L of water to produce a kg of beef LW) in the west was influenced by the larger proportion of beef cattle in this region (84.0% vs. 16.0%),coupled with the fact that a large portion of the crops produced for beef cattle in southern Alberta are irrigated.Levels of precipitation in western Canada during the 2021 growing season were lower than the long-term (i.e., 1981 to 2010) provincial annual average by between 90 and 150 mm, while precipitation levels in eastern Canada were 65-140 mm above the annual average (Statistics Canada 2021c).The lack of precipitation in the west increased reliance on irrigation to provide sufficient water for crop pro-duction, as over 90.0% of all irrigation in Canada occurs in the west (Statistics Canada 2021a).
Nationally, consumption associated with beef duced at farm gate or consumer gate was 657 L kg LW −1 or 1919 L kg CB −1 , respectively, in 2021 (Table 3).These national values, irrespective of functional units, were weighted averages based on the proportion of cattle within each region.In the previous assessment, the water footprint associated with Canadian beef production was estimated to be 631 L kg LW −1 in 2014 (CRSB 2016).Estimates in the previous assessment (CRSB 2016) may have underestimated the amount of forage crops grown under irrigation that were fed to beef cattle, and using the same irrigation intensity (m 3 ha −1 ) for crops in both regions also likely underestimated the national value (CRSB 2016).With the updated methodology and model used in the present analysis, an additional 68 L of water in either the west or east and 3 L less water nationally were required to produce 1 kg of beef LW in 2014 (829, 157, and 654 L kg LW −1 ) compared with 2021.The decrease in water consumption in both regions over the 7-year period could be attributed to improvements in feed efficiency resulting from a 17.1% increase and a 9.3% increase in the average daily gain for the west and east, respectively.In both years, however, a similar trend of greater water consumption was observed in the west than in the east (Fig. 4).Larger proportions of cattle spending more days on irrigated pastures in the west relative to the east may explain this trend.Further, the variation in irrigation intensities of the feed crops that formed a larger proportion of the diets may have influenced the water footprint in the east in both years.The average irrigation intensity based on the product of irrigation intensity (m 3 ha −1 ) and proportion of tame pasture plus hay (comprised the majority of western diets) was 14% greater than the average irrigation intensity of field crops plus hay (comprised the majority of eastern diets) in both years.This effect was also true for yearling-fed production systems, where longer days on pasture led to an additional 213 L of water required to produce the same beef LW, representing a 27.8% increase in the water footprint intensity as compared to the calf-fed system (980 vs. 767 L).
The marginal increase (3.0 L more) in the blue water footprint of Canadian beef production in 2021 relative to 2014, despite the regional decreases in water consumption, was a reflection of differences in the proportions of cattle that were attributed to each region and variation in feed crop yields in each region.Over the 7 years, the proportion of cattle increased in the west from 74% to 84% and decreased in the east from 26% to 16%.Further, comparing 2021 to 2014, the barley yields decreased nationally by 29.7%, while corn yields increased by 7.5% (Statistics Canada 2023).Barley is largely grown in the west, where there are drier conditions, and thus more irrigation is used for crop production.In contrast, corn is predominantly cropped in the east where water needs are largely met by rain.Thus, the marginal impact of Canadian beef cattle production on water footprint over the 7 years suggests a "western effect," with a greater proportion of Canadian beef cattle raised in western Canada fed barley-based diets influencing the water footprint of Canadian beef production.Compared to another Canadian study where national average production data were collected in 2011 (9625 L kg LW −1 ; Legesse et al. 2018), water use intensity at the farm gate was 93.2% lower.Variations in the estimates produced by Legesse et al. (2018) and the present study are due to differences in the system boundaries and LCA methodology employed.Green water (i.e., water from precipitation that is lost through evapotranspiration) was included in the total estimation of water use in the study of Legesse et al. (2018), resulting in a greater water footprint.Excluding green water in the water footprint may overestimate blue water consumption in irrigated regions if the crop water requirements in these regions happen to be met by precipitation.Without green water, Legesse et al. (2018) estimated a lower (223 L kg LW −1 ) blue water footprint of beef cattle production systems in Canada than the present study.Blue water consumption through irrigation was estimated for only the three western provinces (i.e., Alberta, British Columbia, and Saskatchewan) using the application efficiencies of irrigation systems in the former study (i.e., 60%, 75%, and 85% for flood, sprinkler, and center pivot systems, respectively; Legesse et al. 2018).In a USA study, Rotz et al. (2019) also estimated the blue water use of beef production on a weighted average basis by operation type, regional location, and animal numbers in each state, and reported a lower consumption in the eastern USA (northeast and southeast; 203 L kg CW −1 or 120 L kg LW −1 , assuming an average dressing percentage of 59.1%) compared to the west (northwest and southwest; 5614 L kg CW −1 or 3318 L kg LW −1 ).The 88.0% or 96.0%respective reduction in wateruse intensity in the present or the USA study (Rotz et al. 2019) for the eastern versus the western regions of North America is driven by greater precipitation rates reducing the need for irrigation.In North America, beef cattle are usually raised on drier land where crop production for human consumption is often infeasible.Cattle efficiently use forages on these non-arable lands by converting them into animal protein for human consumption.It is expected that where feasible, beef producers in western Canada and the USA will increase the use of irrigation to reduce the risk of drought.Rising global temperatures associated with climate change could also increase the risk of severe droughts, resulting in more irrigation.This trend could invariably increase competition among various end users for water.
With the increasing scarcity of agricultural land, efficient use of land for raising beef is also paramount to Canada's beef industry.Regionally, the land required to produce a kg of beef LW was 72.5% less in eastern as compared to western Canada (43.6 vs. 12.0 m 2 a crop-eq; Table 3).In both regions, pastureland constituted the majority (89.0%west, 77.0% east) of the land base, followed by feed production (11.0%west, 23.0% east; Fig. 3).The greater land use (31.6 m 2 a crop-eq more land base to produce a kg of beef LW) in the west for beef production was primarily influenced by the larger proportion of cattle and more grazing days due to lower land productivity and poor feed quality resulting in lower weight gain in grazing cattle in the west than the east.Legesse et al. (2016) estimated that about 78% of the feed needed by the beef herd in Canada consisted of forage, which is predominantly used in the cow-calf and backgrounding phases.Typically, more land is required for the production of forages than the production of grain for the finishing phase.Compared to the calf-fed systhe yearling-fed system had on average 99 more days on and required an additional 14.1 m 2 a crop-eq of land base to produce a kilogram of beef LW.This resulted in the need for 34.0%(55.5 vs. 41.5 m 2 a crop-eq) more land than the calf-fed system (cow-calf-to-finishing).Raising beef cattle in the yearling-fed production system relies heavily on pasture grazing in the west with more cattle at a lower stocking density than the east.The lower land requirement in the east is also a result of more intensive beef production coupled with improved pasture productivity due to greater precipitation.However, increasing intensive beef production detracts from the unique ability of cattle to utilize poor-quality forages to produce high-quality protein for humans.
Nationally, the land use intensity on a weighted average was 38.7 m 2 a crop-eq kg LW −1 at the farm gate.In 2014, the land area required to produce a kg of beef LW ranged from 37 to 93 m 2 (CRSB 2016).Comparing 2021 to 2014, the land occupation for beef production decreased by 12.4% (43.6 vs. 49.8m 2 a crop-eq LW −1 ) and 13.7% (12.0 vs. 13.9 m 2 a cropeq LW −1 ), in the west and east, respectively, and by 4.4% (38.7 vs. 40.5 m 2 a crop-eq LW −1 ) nationally (Fig. 4).Improved crop yields, decreased days on pasture, and a reduction in the number of grazing cattle over the 7 years accounted for the reduction in the amount of land required for Canadian beef production.Legesse et al. (2016) used average Canadian production data collected in 2011 to estimate the land area required to produce a kg of beef LW to be 104 m 2 (equivalent to 70.3 m 2 a crop-eq LW −1 ), with pastureland accounting for more than 72.0% of this area.In the present study, the average national land use intensity in 2021 was 44.9% lower than the 2011 estimate by Legesse et al. (2016).This difference may be attributed to differences in the system boundaries, production systems, feeding duration, cattle population, and animal performance.For example, our model assumed tame pasture or hay DM intake and native pasture yields for grazing land use estimation, whereas Legesse et al. (2016) used stocking rates (i.e., the number of animals grazing a unit of land for a specified period) that ranged from 1.5 to 5.25 animal unit months.Standardizing the area of grazing land required for beef production using stocking rates may overestimate the required land use if the grazing area is under-utilized (Legesse et al. 2016).Using DM yields for hay or tame and native pastures and considering field and feeding losses as a different approach to estimating land use, Legesse et al. (2016) estimated the land area required to produce a kg of beef LW in 2011 to be 62.0 m 2 kg LW −1 .This is equivalent to 41.9 m 2 a crop-eq LW −1 , assuming 72.0% of the land is pastureland, an estimate similar to ours.A 7.0% greater average LW for cows, steers, and heifers in the present study (664 kg), compared with 2011 (620 kg; Legesse et al. 2016) may also account for the minor variation between studies.The land use intensity for the present study is comparable to other LCA studies conducted for beef cattle in North America.For a production system in the USA, Asem-Hiablie et al. ( 2019) estimated the land use associated with a kg of CB to be 47.4 m 2 a crop-eq, corresponding to 13.7 m 2 a crop-eq kg LW −1 .The lower land-use intensity in the USA is similar to that observed for eastern Canada and is reflective of a more intensive production sys-tem supported by greater levels of precipitation, which support greater forage and feed production per unit of land.
Fossil energy use in the west and east was 0.41 and 0.28 kg oil-eq kg of LW −1 , corresponding to 16.7 and 12.5 MJ, respectively (Table 3).Fossil energy use for the yearling-fed system relative to the calf-fed system was slightly greater (0.53 vs. 0.41 kg oil-eq kg of LW −1 ).The factors contributing to these marginal differences were the amount, type, and source of energy used for crop production (Fig. 3).About 95.0% of the energy use for crop production in the west was associated with the production of barley, while 93.0% of the energy use in the east was associated with corn production.Corn has a greater yield than barley (Statistic Canada 2023), partially accounting for the variation in energy use between the west and east.Direct energy use including natural gas and diesel for the provision of feed and water to cattle, coupled with differences in transportation energy consumption were the additional factors that accounted for differences in energy utilization between the two regions.Comparing 2021 to 2014, the energy footprint intensity was slightly reduced by 0.04 and 0.16 kg oil-eq kg of LW −1 in the west and the east, respectively (Fig. 3).Regional variations in days on feed or in confinement, especially for the yearling-fed system (9 days in the east and 53 days in the west; data not shown) between these 2 years may also account for the slight decline in energy use for Canadian beef production over time.

Water, land, and air pollution
The potential pollution of freshwater in 2021 was marginally greater for the yearling-fed versus the calf-fed production system (3.2 vs. 2.5 g P-eq kg LW −1 ; Fig. 2).In the west, the freshwater eutrophication estimate was 2.4 g P-eq kg LW −1 compared to 3.9 g P-eq kg LW −1 in the east (Table 3).Nationally, a weighted average of 2.6 g P-eq kg LW −1 was observed.Feed production accounted for the majority of this impact (69.0%west, 83.0% east), with the remainder coming from manure on pasture (31.0%west, 17.0% east; Fig. 3).Manure management during confinement was not a contributor to this impact as it was assumed that P losses to freshwater only occurred on pasture.Fertilizers and herbicides were the major pollutants from feed production, along with the erosion of tilled land, with those pollutants largely occurring in the east as a result of greater precipitation.These processes explain the 62.5% increase in pollutant load to freshwater in the east compared to the west.In 2010, a study by AARD ( 2010) observed the freshwater eutrophication potential intensity from beef production to be 1.3 g P-eq kg LW −1 .While the present study used generic crop production data, except for hay production, the AARD (2010) study considered specific data for each crop type.Therefore, it is possible that the current study overestimated P runoff by using generic fertilization rates.Future studies could eliminate this uncertainty by modeling province-specific crop production for key crops, including barley, corn, and wheat.Comparing 2014 to 2021, the freshwater eutrophication indicator in g of P-eq kg of LW −1 was lower in both the west (3.3 vs. 2.4 g P-eq kg LW −1 ) and the east (6.3 vs. 3.9 g P-eq kg LW −1 ) resulting in a decrease from 4.1 to.2.6 g P-eq kg LW −1 , over the 7 years (Fig. 4).An improvement in the precision of fertilizer application, decreased days on pasture, and a in the number grazing cattle could explain this reduction in freshwater eutrophication.
Due to longer days both on pasture and on feed, the terrestrial acidification potential of raising beef cattle in 2021 for the yearling-fed production system was 31.8% greater than for the calf-fed production system (146 vs. 111 g SO 2 -eq kg LW −1 ).In the west, a terrestrial acidification potential of 111 g SO 2eq kg LW −1 was observed as compared to 144 g SO 2 -eq kg LW −1 in the east (Table 3).Consequently, producing a kg of beef LW corresponded to a weighted average of 116 g SO 2eq nationally.Manure deposition during confinement (59.0%west, 63.0% east) and on pasture (22.0%west, 14.0% east), along with the use of fertilizers for feed production (19.0%west, 23.0% east; Fig. 3), contributed to terrestrial acidification mainly through NH 3 emissions.The 29.6% greater emissions observed in the east reflect the fact that cattle spent more time in confinement than in the west.Consequently, the contributions from feed production and manure during confinement were larger in the east than in the west, while the contribution from manure on pasture was greater in the west.Comparing 2021 to 2014, the acidification potential per kg of beef LW was 20.0% (111 vs. 92.5 g SO 2 -eq) greater in the west, 25.2% (144 vs. 115 g SO 2 -eq) greater in the east, and 17.9% (116 vs. 98.4 g SO 2 -eq) greater nationally (Fig. 4).These emissions are directly related to greater NH 3 emissions from stored manure and N fertilizer associated with feed production.The increase in the proportion of calf-fed cattle from 41% to 45% in 2021 coupled with more days in confinement in the west (287 vs. 248 days) and east (304 vs. 273 days) contributed to this increase.Asem-Hiablie et al. ( 2019) estimated an acidification potential of 726 g SO 2 -eq kg of CB −1 or 210 g SO 2 -eq kg of LW −1 for the USA beef production system.While the present study estimated acidification potential from SO 2 (1.0 kg SO 2 kg SO 2 −1 ), NO x (0.7 kg SO 2 kg NO X −1 ), and NH 3 (1.8kg SO 2 kg NH 3 −1 ), the USA study included hydrogen chloride (HCl) emissions (kg SO 2 kg HCl −1 ; Saling et al. 2002).Also, the conversion factor assumed for a kg of beef LW to an edible beef on a consumer plate per mass basis, excluding economic allocation was 0.35 in the current study compared to 0.29 in Asem-Hiablie et al. (2019).This conversion factor suggests greater terrestrial acidification potential post-farm, primarily from fossil fuel use and pre-chain impacts from packaging materials largely due to greater food waste and loss at the consumption phase in the USA supply chain.However, a recent LCA study for USA beef production, where food waste at the consumer level was reduced by half (i.e., from 20.0% to 10.0%), resulted in an 11% reduction in the impact categories including terrestrial acidification (347 vs. 308 g SO 2 -eq kg of CB −1 ; Putman et al. 2023).Furthermore, diets in our study consisted of barley or corn with dried corn distiller's grain, while Asem-Hiablie et al. ( 2019) considered corn diets with wet corn distiller's grain.The greater emissions reported in our study for the east, where corn is commonly grown, align with the greater emissions associated with corn production in the USA (Asem-Hiablie et al. 2019).Overfeeding crude protein (CP), especially from by-products that are high in protein, can also increase NH 3 emissions and contribute to terrestrial acidification (Hristov et al. 2011;Fanchone et al. 2013).Efficient feeding of CP to decrease N excretion while improving the rate of gain can shorten the days on feed and decrease NH 3 emissions.
Emissions into the atmosphere that form photochemical oxidants or smog can also negatively affect human health and the terrestrial ecosystem.In the current study, the potential toxicity to both human health and the health of the terrestrial ecosystem, expressed per kg of beef LW produced at the farm gate, was, on average, 31.1% greater for yearlingfed than calf-fed production systems (11.8 vs. 9.0 g NO x -eq kg LW −1 ).Regionally, the ozone formation potential of 1 kg of LW at the farm gate was 8.8 g NO x -eq kg LW −1 in the west compared to 8.3 g NO x -eq kg in the east, corresponding to a weighted average of 8.7 g NO x -eq kg LW −1 nationally (Table 3).Comparing 2021 to 2014, the photochemical oxidant impact per kg of beef LW was 15.4% (8.8 vs. 10.4 g NO x -eq kg LW −1 ) less in the west, 33.1% (8.3 vs. 12.4 g NOx-eq kg LW −1 ) less in the east, and 20.2% (8.7 vs. 10.9 g NO x -eq kg LW −1 ) less nationally (Fig. 4).Large emissions of photochemical oxidants were mainly associated with fertilizer and herbicide use for feed production (Fig. 3).This suggests that increased crop yields, coupled with decreased fertilizer and herbicide application, along with a reduction in the number of cattle on pasture with improved efficiency per hectare account for the lower photochemical oxidant formation in 2021 compared to 2014.

Sensitivity analyses
Sensitivity indices were developed for the end-weights of each cattle category for the environmental indicators.Baseline end-weights were defined using an analysis of commercially relevant Canadian cattle finishing data (i.e., 5-year average data used for 2021 (2015-2020) and 2014(2010-2014);Brenna Grant, Canfax Research Services, and Feedlot Health Management Services, personal communication, 2022).The sensitivity analysis was conducted by increasing and decreasing these baseline end-weights within a 10% range, while keeping the production period constant.In general, a 10% increase in the end-weights reduced the environmental impacts of beef production from 0.2% to 8.1% and 0.1% to 7.7% in the west and east, respectively (Figs.S1 and S2).The largest reductions were observed for the carbon footprint, land use, and terrestrial acidification.The least sensitive indicators were fossil fuel depletion and photochemical oxidant formation.The reduction is signalled by the greater efficiency of the system with greater CWs with constant days on feed.This shows that if the industry continues to increase CW through the adoption of efficient production practices, it will reduce the carbon footprint, land use, and acidification, as long as feed efficiency remains constant or further improves.

Impact reduction opportunities
Several strategies exist for mitigating the environmental footprint throughout the life cycle of beef.However, due to differences in production systems and regional variation, the magnitude of environmental impact and extent of adoption will depend on the value of the mitigation strategy to each cattle production system.Feed production was the most significant contributor the majority of the indicators assessed in this study.This includes fossil fuel depletion due to energy required for crop production, water consumption due to irrigation in the west, and freshwater eutrophication, and photochemical oxidant formation due to fertilizer and pesticide use.In addition, feed quality and intake can affect enteric CH 4 emissions, which are the largest contributor to the carbon footprint of the beef industry, followed by manure emissions.It is important to consider that the production of food on this land for humans would likely generate a similar or even higher environmental footprint than when it is used to produce feed for beef cattle.Intensification of cattle production systems through improved feeding and management practices, including the use of productivity-enhancing technologies, can increase the rate of gain resulting in fewer days in confinement or on pasture.Such intensification can reduce enteric CH 4 emissions and lower the contribution of feed to the environmental footprint.However, absolute enteric CH 4 emissions may not always decrease.Thus, supplementation with safe and approved feed additives labelled for enteric emission reduction could substantially reduce GHG emissions.For instance, 3-Nitrooxypropanol (3-NOP) is reported to decrease enteric CH 4 emissions by 30%-80% (Yu et al. 2021).Further, because of the low recommended dosage of 3-NOP in cattle diets (i.e., 0.006% to 0.02%), emissions associated with the manufacturing and transportation of this additive are low, accounting for only 1.8 and 5.3%, respectively, of its CH 4 reduction potential (Beauchemin et al. 2022).3-NOP has been approved for use in ruminants in the European Union, Chile, Australia, Mexico, and Brazil, and is under consideration in the USA and Canada.However, potential barriers to on-farm adoption include cost/lack of financial incentives, consumer acceptance, and its application in grazing systems.Diverting food waste and by-products from landfills and feeding them to beef cattle may be another approach to reducing the environmental impact of beef production.However, incorporating byproducts in beef diets should be balanced, particularly for protein so that animal requirements are met and the amount of N excreted in cattle manure does not result in heightened NH 3 and N 2 O emissions.Beneficial management practices, such as integrated pest management (IPM) and 4R nutrient stewardship can also decrease fertilizer, herbicide, and energy use in crop production systems.
While water use for Canadian beef appears lower than in many other beef-producing countries, improved efficiency at the crop production level is necessary.Water for irrigation was the primary water use, mainly in the drier areas in the west.More efficient irrigation equipment and the conversion of canal to pipeline systems should continue to be adopted in the west to reduce water use in beef production.
It is not immediately clear if certain practices are sustainable, despite their ability to lower the environmental footprint.For example, beef from dairy origin at the expense of beef from traditional production systems may have environmental benefits to the beef industry, mainly due to a decrease in the number of traditional beef breeding herds cou-pled with the majority of the emissions from dairy beef being allocated to milk production.However, the lower birth weight and rate of gain of dairy breeds compared to beef breeds may have a negative impact on both meat quality and GHG emissions.Consequently, the lack of an effect of dairy beef on GHG emission intensities coupled with its perceived lower meat quality may fuel public criticism about the beef industry's environmental sustainability goals.To curb these future concerns, selective breeding using semen from beef bulls with superior growth and carcass characteristic traits on superior dairy cows may produce calves with the potential for optimum milk production while satisfying consumer expectations for meat quality and a lower carbon footprint.Comparing the calf-fed versus yearling-fed systems revealed generally greater impacts for the yearling-fed system, but it did not account for other ecological benefits including improved biodiversity, soil health, and the carbon sequestration that can occur when cropped lands are returned to perennial forage.Moreover, increasing intensive beef production detracts from the unique ability of cattle to utilize poor-quality forages to produce high-quality protein for humans.Therefore, future assessments that consider biodiversity, as well as economic and social factors should be considered.

Conclusion
The assessment of the environmental impacts of traditional beef cattle production in Canada showed that feed production had the greatest impact on most environmental indicators.The GHG emission intensity, without including dairy meat, was 10.4 kg CO 2 -eq kg LW −1 at the farm gate, corresponding to 32.8 kg CO 2 -eq kg CB −1 at the consumer plate.Adding dairy meat to the production chain decreased the GHG emission intensity by 5.8% nationally (0.6 kg CO 2 -eq kg LW −1 less).Other environmental metrics expressed per kg of LW produced were 657 L, 38.7 m 2 annual crop-eq, 0.4 kg oileq, 2.6 kg P-eq, 115.9 kg SO 2 -eq, and 8.7 kg NO x -eq for water use, land use, fossil fuel use, freshwater eutrophication, terrestrial acidification, and photochemical oxidation, respectively.Compared to the last CRSB assessment in 2014, the carbon footprint for producing a kilogram LW of beef in 2021 was 21.0% less in the east (2.6 kg CO 2 -eq less) and 17.3% less in the west (2.2 kg CO 2 -eq less), indicating a national decline of 17.5% (2.6 kg CO 2 -eq less).Likewise, resource use intensities, including water, land, and fossil fuel use at the farm gate, decreased regionally, ranging from 8.1% to 42.3%.The intensity of other environmental indicators, including water and air pollutants also decreased by 15.4% to 38.1% within this same period.These data provide a benchmark for future regional and national assessments and evaluation of the potential benefits of mitigation strategies.This also provides information to support the future development of a more comprehensive and descriptive LCA of Canadian beef.
provision of data when published information was unavailable and the producers who contributed to the survey We are also grateful Brenna Grant (Manager of Canfax Research Service) and others of the Scientific Advisory Committee (SAC) of the Canadian Roundtable for Sustainable Beef (CRSB) for their help in obtaining information and supporting this study.

Fig. 1 .
Fig. 1.An overview of the Canadian beef life cycle analysis including inputs and outputs of phases, and impacts measured.Retail and consumer transportation was excluded and dairy cattle production data included cows, heifers, and steers sourced from Dairy Farmers of Canada (DFC 2018).

Fig. 2 .
Fig. 2. Percentage contribution of the beef production chain for each of the environmental impact metrics per kilogram of consumed boneless beef in the western (A) or eastern (B) regions of Canada.

Fig. 4 .
Fig. 4. Regional environmental footprint of the Canadian beef production system in 2014 versus 2021 production year per live weight (LW) kilogram of beef.

Table 1 .
The production parameters and phases of raising steers and heifers in western and eastern Canada a .

Table 2 .
Population of slaughtered cattle and beef carcass data used as model inputs for the 2021 production year.

Table 3 .
Environmental footprint intensity of national, western, and eastern beef production in Canada.