This fortnightly newsletter was curated and edited by: J.W. Holloway and his Team
Synopsis
Consumers often perceive without the benefit of science, lacking a basis of historical facts, for instance incorrectly, that the modern beef production system has an environmental impact far greater than that of historical systems, with improved efficiency being achieved at the expense of greenhouse gas emissions. This article summarizes the research reported by Capper et al. (2009). The objective of this study was to compare the facts of the environmental impact of modern (2007) United States (US) beef production with production practices characteristic of the US beef system in 1977. A deterministic model based on the metabolism and nutrient requirements of the beef population was used to quantify resource inputs and waste outputs per (1) one billion kilograms (kg) of beef. Both the modern and historical production systems were modeled using characteristic management practices, population dynamics, and production data from US beef systems. Modern beef production requires considerably fewer resources than the equivalent system in 1977, with (4) logical measures for comparison.
Modern production resources require (69.9%) sixty-six-point nine percent of animals, (81.4%) eighty-one-point four percent of feedstuffs, (87.9%) eighty-seven-point nine percent of the water, and only (67.0%) sixty-seven percent of the land required to produce (1) one billion kg of beef. Waste outputs constitute additional measures, which were similarly reduced, with modern beef systems producing (81.9%) eighty-one-point nine percent of the manure, (82.3%) eighty-two-point three percent of the CH4, and (88.0%) eighty-eight percent of the N2O per billion kilograms of beef compared with production systems in 1977. The C footprint per billion kilograms of beef produced in 2007 was reduced by (16.3%) sixteen-point three percent compared with equivalent beef production in 1977. Noteworthy, as the US population increases, it is crucial to continue the improvements in efficiency and production volume illustrations. Improvement measures demonstrated over the past (30 yr.) thirty years include those to maintain and in fact increase the supply for the market demand for safe, affordable beef while reducing resource use and mitigating environmental impact.
Commentary
This limited series of the occasional e-letters are comprised of (2) two articles. They will appear fortnightly and are published during July, though they will be accessible through our social media pages. How did the environmental impact of beef production evolve in (30) thirty years? We will investigate the question in (3) three steps. Firstly, understanding the characteristics of the beef production system in 2007. Secondly, what was the beef production characteristics in 1977? Finally, a comparison of the resource inputs and waste outputs between the (2) two periods. We would like to bring to your attention that this aggregation of knowledge remains true and evolutive even if a decade or so has passed.
Analysis
This study used data from existing reports and databases and required no Animal Care and Use Committee approval. A deterministic model based on the nutrient requirements and metabolism of animals within all sectors of the beef production system was used to quantify the environmental impact (defined as resource use and waste output per unit of beef) of the US beef industries in 1977 and 2007. The model employed a whole system approach founded on life cycle assessment principles whereby all relevant inputs and outputs from the beef production system were included with the system. Conventional beef production systems within the United States consisted of (3) major animal-based subsystems. The cow-calf unit contained animals that served to support population dynamics (cows, calves, replacement heifers, adolescent bulls, yearling bulls, and mature bulls). The stocker/backgrounder operation contained weaned steers and heifers fed until they reached sufficient BW to be placed into the feedlot.
The feedlot contains both calf-fed (beef and dairy animals that enter at weaning) and yearling-fed (beef animals that enter after the stocker stage) animals that were fed until the desired BW and slaughter finish was achieved. It is acknowledged that small niche markets exist within US beef production whereby animals are finished in pasture-based or organic systems. However, these systems comprise only (3%) three percent of beef produced in modern systems (USDA/ERS, 2010b) and equivalent data were not available for 1977. Given the preponderance of the aforementioned conventional production system within the beef industry, this was considered to provide a representative example of the difference between the (2) two-time points. Primary inputs into these subsystems included animal feed and drinking water, unit electricity, and fuel for animal transport between subsystems and feed transport to farm.
Secondary inputs included chemicals (fertilizer, pesticides) applied to feed crops, irrigation water, and fuel for cropping practices and agrochemical manufacture. Nutrient requirements of individual animals were calculated using AMTS Cattle Pro (2006), a commercial cattle diet formulation software based on the Cornell Net Carbohydrate and Protein System. Animal diets were formulated to fulfill the requirements of animals within each subsystem according to age, sex, breed, BW, and production level. Environmental impact was assessed by comparing annual resource inputs and waste output of the US beef production systems in 1977 and 2007 and expressed per billion kilograms of HCW beef produced in 365 d. The US beef industry includes animal inputs from the US dairy industry in terms of cull cows (both 1977 and 2007), plus male and female calves at 3 d of age (2007 only). Resource inputs and waste output between the dairy and beef systems were calculated based upon a biological allocation method.
A deterministic model of resource use and environmental impact within dairy production was previously developed by Capper et al. (2009), based upon the same nutrition and metabolism principles as the current beef model. Employing the model described by Capper et al. (2009) ensured that resource input data for both models were sourced from similar data, thus minimizing conflict between the models. The dairy model was used to determine the proportion of total resource inputs and waste output attributable to growth in Holstein heifers from birth up to 544 kg (the BW at which they would be sold as beef animals if they did not enter the dairy herd). These totals represented the environmental cost attributed to dairy cull cows entering the beef market. They were applied to the appropriate beef production according to the number of cull cows within each system.
The additional cost of producing male and female dairy calves for calf-fed rearing within the 2007 beef production system was calculated by partitioning out the proportion of total resource inputs and waste output attributable to pregnancy in lactating and dry dairy cows. This cost was adjusted for the number of dairy calves in the beef system, and thus the number of cows required, before application to the beef production system.
2007 Beef Production System Characteristics
The 2007 beef production system was modeled according to characteristic US production practices (USDA, 2000a,b, 2009a,b) with the total environmental impact based on national beef production and animal numbers (USDA/NASS, 2008). Total beef production in 2007 equaled 11.9 billion kilograms from 33.7 million animals slaughtered. The slaughter population was made up of 17.3 million steers, 10.2 million heifers, 2.5 million dairy cows, 3.2 million beef cows, and 554 thousand bulls. Data from USDA (2009b) indicated that the majority of beef animals in the United States consisted of British breeds. Thus, beef cows and replacement heifers were assumed to be pure-bred Angus, bulls were purebred Hereford, and beef steers and heifers destined for slaughter were Angus × Hereford cross-bred animals. Relative proportions of cows, heifers, and bulls within the support population were based on USDA/NASS (2007b) data, with 89% of cows and heifers calving, of which 96.5% bore a live calf (USDA, 2009b).
Animal numbers were prorated to a 365-d total according to the amount of time spent within each subsystem. Lactating cows grazed pasture ad libitum with a DMI based on 567 kg of BW, an annual lactation length of 207 d (USDA, 2009a), milk yield of 1,625 kg/lactation (Miller and Wilton, 1999; Miller et al., 1999), and milk composition of 4.03% fat and 3.38% protein (NRC, 2000). Dry cow DMI was calculated for a pasture, straw, and grass hay diet adjusted for a 42-kg average calf birth BW and 158-d dry period. Nutrient requirements for dry cows were based on an average of 201 d of gestation. The average dry cow in the analysis was at d 201 of gestation (83 d into the 158-d dry period). The assumed calving interval was 12 mo (365 d). Replacement heifers were included in the population at a rate of 0.27 heifers per cow with an annual replacement rate of 12.9% and a 24 mo age at first calving. Heifers were fed a pasture, grass hay, and straw diet adjusted for a predominantly pasture-based diet during the spring and summer, with conserved forage supplementation during fall and winter.
Heifer growth rates averaged 0.54 kg/d from birth to 454 kg at first calving (BW minus calf BW). Diets for bulls were formulated on the same basis as the replacement heifer diets, with DMI based on median BW of 907 kg (mature), 714 kg (yearling), and 339 kg (adolescent). Adolescent bulls were considered to transfer to the yearling group at 24 mo of age and 635 kg of BW; yearling bulls were considered mature at 36 mo and 794 kg of BW. Artificial insemination is only used in 2.9% of animals within the US beef herd (USDA, 2009b); therefore, the maintenance requirement for mature and yearling bulls was adjusted for the activity required to service cows at ratios of 23.7 cows: mature bull and 16.3 cows: yearling bull (USDA, 2009b). Before weaning at 207 d (USDA, 2009a), beef calves suckled from the dam. They consumed pasture and starter feed (flaked corn and soybean meal) at intakes calculated according to the Agricultural Modeling and Training Systems (AMTS) Cattle Pro (AMTS, 2006) nutrient requirements for calves with median BW of 148 kg (steers) and 137 kg (heifers) growing at 0.98 and 0.89 kg/d, respectively.
Post-weaning, 83.5% of calves (personal communication, Tom Field, National Cattlemen’s Beef Association, Denver, CO) entered the stocker subsystem where they were fed diets that consisted of pasture, grass hay, corn silage, flaked corn, and soybean meal according to seasonal pasture availability. Intakes were calculated and diets balanced for median BW of 320 and 290 kg, and growth rates of 0.80 and 0.69 kg/d for steers and heifers, respectively. At 12 mo of age and a median BW of 370 kg, the stockers entered the feedlot as yearling-fed finishing animals. Diets for yearling-fed feedlot steers and heifers were balanced for median BW and growth rates (510 kg and 1.59 kg/d for steers; 446 kg and 1.42 kg/d for heifers, respectively), based on DMI for a finishing diet consisting of corn grain, soybean meal, alfalfa hay, and vitamin/ mineral supplements. Yearling-fed steers spent 151 d on feed, whereas yearling-fed heifers spent 138 d on feed before slaughter at 635 and 544 kg, respectively.
Approximately 16.5% (personal communication, Tom Field, National Cattlemen’s Beef Association, Denver, CO) of weaned beef calves enter the feedlot directly as calf-fed finishing animals. Calf-fed feedlot animals were fed a diet containing the same base ingredients as the yearling-fed animals, but formulated for overall weaning to slaughter growth rates of 1.37 kg/d (steers) and 1.22 kg/d (heifers). Intakes were calculated for median BW of 445 and 389 kg for steers and heifers, respectively. Calf-fed animals were slaughtered after 268 days on feed at 635 kg (steers) or 244 d on feed at 544 kg (heifers). According to USDA (2000a), 12.9% of animals placed in feedlots originated from dairy operations. Given the ratio of male: female dairy animals placed in finishing operations, 11.5% of all feedlot animals are dairy steers, and 1.4% of all feedlot animals are dairy heifers. Given that the current US dairy herd contains ~90% Holstein animals (USDA, 2007), all dairy animals entering the beef system were assumed to be pure-bred Holsteins.
Within the current model, dairy calves were fed surplus milk and a calf starter ration (flaked corn and soybean meal) from 3 d of age until weaning at 56 d. Dairy calves entered the feedlot on a calf-fed basis at 93 kg (steers) and 86 kg (heifers) and were finished on a standard feedlot diet similar to that fed to the calf-fed beef animals, balanced for overall growth rates of 1.41 and 1.24 kg/d for steers and heifers, respectively. Calf-fed dairy animals spent an average of 307 d on feed and were slaughtered at 544 kg (steers) or 499 kg (heifers). Growth rates predicted by AMTS (2006) throughout the entire beef production system allowed animals to finish at an average of 16 mo of age. Productivity-enhancing technologies, including hormone implants, ionophores, β-adrenergic agonists, and in-feed hormones were available for use by the beef industry in both 2007 and 1977. However, diets were formulated without the use of productivity-enhancing technologies because of a lack of reliable adoption data for different technology categories and time points.
The slaughter population for 2007 consisted of calf-fed and yearling-fed beef steers and heifers, calf-fed dairy animals (both steers and heifers), and cull animals from the beef and dairy sectors (cows and bulls). The average BW at slaughter was 607 kg.
1977 Beef Production System Characteristics
The year 1977 was chosen as a suitable time point for comparison because the ratio of growing beef animals (steers and heifers) to cull animals (cows and bulls) was representative of the average of all annual time points between 1970 and 1980 at 0.76 growing animals:0.24 cull animals (USDA/NASS, 2010). The 1977 beef production system was largely similar to the 2007 system; the majority of animals were produced within the conventional cow-calf/stocker/feedlot structure. Nonetheless, some notable exceptions exist: the practice of weaned calves proceeding directly to the feedlot for finishing was not practiced, and surplus dairy calves were directed into the US veal market. In 1977, 10.6 billion kilograms of beef was produced from 38.7 million animals slaughtered. The slaughter population was made up of 17.9 million steers, 10.9 million heifers, 1.9 million dairy cows, 7.2 million beef cows, and 832 thousand bulls.
Literature from the time-period indicated that the traditional British beef breeds predominated in 1977 (Kratz et al., 1977). Thus, for modeling purposes, beef cows and replacement heifers were assumed to be purebred Angus, bulls were pure-bred Hereford, and beef steers and heifers destined for slaughter were Angus Hereford cross-bred animals. Relative proportions of cows, heifers, and bulls within the support population were based on data from Wiltbank (1970, 1974). Animal numbers were prorated to a 365-d total according to the amount of time spent within each subsystem. Within the cow-calf subsystem, lactating cows grazed pasture ad libitum with DMI based on 454 kg of BW and an annual lactation length of 205 d (Sellers et al., 1970). In the absence of time point-specific data, and because milk yield has not been a major selection goal for beef cattle over the past decades, a milk yield of 1,625 kg/lactation (Miller and Wilton, 1999) and milk composition of 4.03% fat and 3.38% protein (NRC, 2000) were assumed to be representative of 1977.
Nutrient requirements for dry cows were based on an average of 201 d of gestation. The average dry cow in the analysis was at d 201 of gestation (83 d into the 158-d dry period). The assumed calving interval was 12 mo (365 d) Dry cow diets were formulated based on pasture, straw, and grass hay, with DMI adjusted for a 33-kg average calf birth BW and 160-d dry period. Replacement heifers were included in the population at rates according to USDA data for 1977 heifer numbers (USDA, 1977), with an annual replacement rate of 12.9% and a 24-mo age at first calving. Heifer diets were formulated based on a predominantly pasture-based diet during the spring and summer, with conserved forage (grass hay, straw) supplementation during fall and winter. Heifer growth rates averaged 0.44 kg/d from birth to 363 kg at first calving (BW minus calf BW). To agree with USDA (1977) data, beef bulls were included in the population at a rate of 23.3 cows: mature bull and 16 cows: yearling bull.
Bull diets for bulls were formulated upon the same basis as the replacement heifer diets, with DMI based on median BW of 726 kg (mature), 572 kg (yearling), and 271 kg (adolescent). Adolescent bulls transferred to the yearling group at 24 mo of age, and 508 kg of BW, yearling bulls were considered mature at 36 mo and 635 kg of BW. Maintenance requirements for mature and yearling bulls were adjusted for the activity required to service cows at the aforementioned ratios. Within the 1977 cow-calf subsystem, calves suckled from the dam, with daily intakes predicted by AMTS Cattle Pro (2006) according to average cow milk component yield, with supplemental nutrients provided by grazed pasture. Nutrient requirements were based upon steer calves with median BW of 108 kg and a growth rate of 0.69 kg/d, and heifer calves at 96 kg of median BW growing at 0.59 kg/d. Calves were weaned at 205 d (Sellers et al., 1970) and entered the stocker subsystem.
Diets within this system consisted of pasture, grass hay, corn silage, flaked corn, and soybean meal according to seasonal pasture availability. Steers within the stocker subsystem had a median BW of 238 kg and a growth rate of 0.48 kg/d, whereas heifers weighed 215 kg at the mid-point and grew at 0.42 kg/d. Steer stockers entered the feedlot as yearling-fed finishing animals at 14 mo of age with a median BW of 295 kg. Heifers entered this system at 15 mo of age, at 272 kg. Yearling-fed feedlot animals were fed finishing diets for ad libitum intake consisting of corn grain, soybean meal, alfalfa hay, and vitamin/mineral supplements, formulated to allow 1.40 kg/d growth rate in steers (median BW 397 kg) and 1.21 kg/d growth in heifers (median BW 340 kg). Yearling-fed steers and heifers remained in the feedlot for 173 and 149 d, respectively, before slaughter at 499 kg (steers) and 408 kg (heifers).
Growth rates predicted by AMTS (2006) throughout the entire beef production system allowed animals to finish at an average of 20 mo of age. The slaughter population for 1977 consisted of yearling-fed beef steers and heifers and cull animals from the beef and dairy sectors (cows and bulls). The average BW at slaughter was 468 kg.
Resource Inputs & Waste Outputs
Manure production, N excretion, and P excretion for animals within each subsystem were calculated according to the animal and diet-specific output values from AMTS (2006). Dietary soluble residue, hemicellulose, and cellulose intakes were used to calculate enteric CH4 production from all animals within each subsystem, including pre-weaned calves (Moe and Tyrrell, 1979). The fraction of N emitted as enteric N2O was modeled using data reported by Kaspar and Tiedje (1981) and Kirchgessner et al. (1991). Emissions of CH4 from manure were estimated using methodology prescribed by the US Environmental Protection Agency (US EPA, 2010) based on the quantity of volatile solids excreted, maximum CH4-producing potential (0.24 m3 per kilogram of volatile solids), and a conversion factor for pasture-based or feedlot systems. Intergovernmental Panel on Climate Change (IPCC, 2006) emission factors were used to calculate N2O emissions from manure.
Biogenic C, which rotates continuously through the relatively short-term cycle between the atmosphere, into crops and animals, and back to the atmosphere through animal respiration, was considered to be neutral with respect to GHG emissions. Carbon sequestration into soil and CO2 produced through animal respiration were considered to balance and were not specifically accounted for. The time point-specific population beef data gathered for 1977 and 2007 was based on animal numbers from January 1 to December 31 for each year. The majority of supplemental feed supplied to animals within this data set would have been harvested in 1976 and 2006. Therefore, total land use was derived from a function of the annual whole population feed requirement and published crop yields for these years according to USDA/ NASS (2010; http://www.nass.usda.gov/Data_and_ Statistics/Quick Stats/#top). Fertilizer application rates for crop production during 2006 were taken from the most recently published US data for corn (USDA/ NASS, 2006) and soybeans (USDA/NASS, 2007a).
Equivalent data for 1976 crop production was sourced from USDA/ERS (USDA/ERS, 2010a). Data for alfalfa and grass hay inputs were according to Pimentel and Pimentel (2007) and Barnhart et al. (2008). Wheat straw was considered to be a by-product of wheat production, and all fertilizer inputs were allocated to the grain portion of the wheat crop. Emissions of N2O from fertilizer application, manure application to crops, and manure applied while grazing was estimated from the factors published by the IPCC (2006). Emissions of CO2 from fertilizer and pesticide manufacture were derived from West and Marland (2002), and similar emissions from fossil fuel combustion for crop production were calculated from US EPA (2010). Pasture-based US beef production systems originally served to use land that was unsuitable for crop production because of characteristics such as unfavorable topography or soil type (Cardon et al., 1939).
For the purposes of this study, all pasture was considered to be permanent (i.e., present as pasture and undisturbed by tillage for >25 yr). Mature temperate pasture subject to biomass removal by grazing/haying (Skinner, 2008) or burning (Sukyer and Verma, 2001) is considered to have a net C balance close to zero. Sequestration occurring as a result of land-use change is a dynamic process following a logarithmic decay curve. Because of a lack of reliable data and the number of assumptions involved in applying a land-use factor to cropland, C sequestered into the soil was not included in the model calculations for either time point. Voluntary water intake for mature cows was modeled according to Beckett and Oltjen (1993), with water intakes for all other classes of animals calculated from the equation derived by Meyer et al. (2006). Data relating to irrigation water application rate and usage was sourced from the Census of Agriculture Ranch and Irrigation Surveys from 1979 and 2007 (USDA/NASS, 1979, 2007c).
Annual electricity use for cattle feedlots was 326 kWh per animal, prorated, according to BW (Luding ton and Peterson, 2005). Data from the Energy Information Administration (2001) provided the data from which to calculate a nationwide factor for CO2 emissions from electricity generation, which was applied to electricity use within the model. There is a paucity of information available on the distances traveled by animals between subsystems within either the 1977 and 2007 production system. As noted by Forde et al. (1998), improving the quality of data available would have benefits in terms of tracking animal movements and disease. From examining the major states involved with cow-calf, stocker, and feedlot production at both time points, it seems unlikely that, for reasons of animal welfare and economic cost, animals would be moved between the furthest points. A value of 483 km was therefore adopted as the average distance for animal movements between the cow-calf, stocker, and feedlot operations for both 1977 and 2007.
According to Shields and Mathews (2003), few animals traveled more than 161 km between the feedlot and slaughter plant; therefore, this distance was adopted for the final transportation stage in both years. Energy use for corn transportation was generated by comparing the major corn-producing states with those containing the greatest number of feedlot animals for each year. Assuming that moving corn for the shortest distance was the most economically favorable solution within both 1977 and 2007, weighted averages for in-state transport (set at 161 km) and out-of-state transport (distance from the center of 1 feedlot state to the center of the nearest corn-producing state) based on the proportion of total beef produced within each state were calculated. The final average transport distances for corn were 420 km (1977) and 558 km (2007). Energy use and CO2 emissions from transport were based on the average fuel efficiency and carrying capacity of transport vehicles representative of those used for animals or grain in 1977 and 2007 (USDA/ERS, 1975; Grandin, 2001; Davis et al., 2009).
The total C footprint was calculated by applying CO2-equivalent factors from IPCC (2007) to CH4 (25) and N2O (298) to calculate the total C footprint as the sum of all CH4, N2O, and CO2 emissions expressed in CO2-equivalents.
Conclusion
The environmental impact of animal husbandry, intensive or extensive, includes the consumption of water and energy, risk of degradation of water quality, and substitution of forests by meadows intended for animal production; or meadows by annual crops for animal feed. The impact depends specifically on the type of farming: -Intensive farming, based on the concentration of animals confined in closed buildings or parks, fed with feed distributed by the breeder. In traditional intensive systems, only monogastric animals such as poultry or pork were reared. This system had an important function of recycling food production waste (kitchen waste, cereal bran, spoiled food, crop residues, forest products like oak acorns) which made it possible to avoid diverting directly usable food for human nutrition. In modern systems, intensive plant crops feed intensive farming of almost all species (only a few species such as goose, sheep, and goats do not support this mode of production) using modern techniques.
Thermo-regulated buildings and ventilated, above-ground system, fossil fuels, machinery, chemical and mineral fertilizers, pesticides. In these farms, the main problem is the management of effluents and the classic risks associated with intensive farming. Extensive breeding is based on the free movement or parking of animals in pastures, i.e., natural or artificial meadows (i.e., sown with grazable plant species chosen and maintained by the breeder). These systems have changed little with the contribution of modern techniques and remain very close to pre-industrial systems. In general, they do not use chemical fertilizers or pesticides, which explains, in particular, the frequent conversions in organic farming of cattle rearing on the grass. The main risk of extensive farming is poor regulation of the livestock load in space and time, which can cause damage in the event of overgrazing2 but also nitrogen emissions, including in organic farming3.
It is the intensive farming method that brings together the majority of environmental nuisances in developed countries. In emerging countries, it is rather extensive farming that poses problems of spatial influence, degradation of natural vegetation, and competition for water in arid zones. Methane discharges are not inevitable, and they are the result of too low a yield from the fermentation of ruminants. Many ways of research are based on several factors: the given food, food supplements, bacteria, and symbionts of the digestive system and finally, animal genetics modifications. Methane emissions represent 2 to 12% of the energy absorbed by ruminants, the margin for progress is very real, and we will discuss the result of our study in the next E-letter!
We want to proceed further, more in-depth on this controversial subject. Therefore, please follow us on social media and join us on the (15th) fifteenth of the month for Part (2!) two to learn more about the environmental impact of beef production. Thereafter, please join us on the (1st) first and (15th) fifteenth of each month for our fortnightly delivery of insightful, informative must-reads from some of the world’s scientific thinkers. Selected by our editors is a collection of current topics with a profound ability for beneficial improvements, guidelines, and process practices. Thank you for reading our publication entirely; please share it with others who also care. We look forward to your comments and having you with us again fortnightly; we will be thrilled in having you with us; thus, we will take your trust in us with great honor and appreciation.
