Greenhouse Gas Emissions from Calf- and Yearling-Fed Beef Production Systems, With and Without the Use of Growth Promotants

A review of emerging technologies, nutritional practices, and management strategies to improve intramuscular fat composition in beef cattle

The flavour, tenderness and juiciness of the beef are all impacted by the composition of the intramuscular fat (IMF), which is a key determinant of beef quality. Thus, enhancing the IMF composition of beef cattle has become a major area of research. Consequently, the aim of this paper was to provide insight and synthesis into the emerging technologies, nutritional practices and management strategies to improve IMF composition in beef cattle. This review paper examined the current knowledge of management techniques and nutritional approaches relevant to cattle farming in the beef industry. It includes a thorough investigation of animal handling, weaning age, castration, breed selection, sex determination, environmental factors, grazing methods, slaughter weight and age. Additionally, it rigorously explored dietary energy levels and optimization of fatty acid profiles, as well as the use of feed additives and hormone implant techniques with their associated regulations. The paper also delved into emerging technologies that are shaping future beef production, such as genomic selection methods, genome editing techniques, epigenomic analyses, microbiome manipulation strategies, transcriptomic profiling approaches and metabolomics analyses. In conclusion, a holistic approach combining genomic, nutritional and management strategies is imperative for achieving targeted IMF content and ensuring high-quality beef production.

Climate impacts of alternative beef production systems depend on the functional unit used: Weight or monetary value

Beef production has been identified as a significant source of anthropogenic greenhouse gas (GHG) emissions in the agricultural sector. United States and Canada account for about a quarter of the world's beef supply. To compare the GHG emission contributions of alternative beef production systems, we conducted a meta-analysis of 32 studies that were conducted between 2001 and 2023. Results indicated that GHG emissions from beef production in North America varied almost fourfold from 10.2 to 37.6 with an average of 21.4 kg CO2e/kg carcass weight (CW). Studies that considered soil C sequestration (C-seq) reported the highest mitigation potential in GHG emissions (80%), followed by growth enhancement technology (16%), diet modification (6%), and grazing management improvement (7%). Our study highlights the implications of using carbon intensity per economic activity (i.e., GHG emissions per monetary unit), compared to the more common metric of intensity on per weight of product basis (GHG emissions per kg CW) for comparisons across differentiated beef cattle products. While a positive association was found between the proportion of lifespan on grassland and the conventional weight-based indicator, grass-finished beef was found to have lower carbon intensity per economic activity than feedlot-finished beef. Our study emphasizes the need to incorporate land use and management effects and soil C-seq as fundamental aspects of beef GHG emissions and mitigation assessments.

Relationship among cattle breed and anabolic implant protocol relative to feedlot performance: Growth, temperament, feeding behavior, carcass traits, and economic return

Recent research has suggested that different cattle breed types may respond differently to anabolic implant protocols of varying intensity. Therefore, the purpose of this research was to compare anabolic implant protocols in feedlot steers of 2 different breed types. Sixty steers were stratified by weight and breed in a 2 × 3 factorial design examining 2 different breeds: Angus (AN; n=38) or Santa Gertrudis influenced (SG; n=22), and 3 implant strategies: no implant (CON; n=20), a moderate intensity implant protocol (d0 implant: Revalor-G, d56 implant: Revalor-IS, d112 implant: Revalor-S; MI; n=20), or a high intensity implant protocol (d0 implant: Revalor-IS, d56 implant: Revalor-S, d112 implant: Revalor-200; HI; n=20). Steers were randomly placed into pens equipped with GrowSafe bunks to collect dry matter intake and feeding behavior. All animals were fed the same diet. Weight, chute score, exit velocity, serum, rectal temperature, hip height and 12th rib fat thickness were collected approximately every 28 d over a 196 d period. Serum urea nitrogen (SUN) was evaluated as well. Total average daily gain was increased (P < 0.0001) in both the HI and MI steers compared to the CON steers by 29.4% and 26%, respectively. A treatment × breed interaction was observed (P < 0.0001) for hip height, with AN-CON steers being shorter (P < 0.0007) than AN-HI, SG-CON, SG-MI, and SG-HI steers. A breed × treatment interaction was observed (P < 0.004) for chute score and rectal temperature, with SG-HI and SG-MI steers having increased chute scores (P < 0.001) when compared to AN-HI, AN-MI, AN-CON, and SG-CON throughout the course of the trial. Additionally, SG-HI and SG-MI steers had an increased rectal temperature (P < 0.004) compared to AN-HI, AN-MI, AN-CON, and SG-CON steers. A breed effect was observed (P = 0.002) for SUN with AN steers having increased (P = 0.002) SUN concentration compared to SG sired steers, in addition to a treatment effect (P < 0.0001), with CON steers having a higher (P < 0.0001) SUN concentration than MI and HI steers, regardless of breed. The MI implant protocol increased net return per head, on average, by $97.28, regardless of breed, while the HI implant protocol increased net return by only $80.84. Taken together, despite the cattle breed types responding differently to the different anabolic implant protocols at times, a moderate intensity anabolic implant protocol was optimal in this experiment for steers raised in a temperate climate.

Evaluation of growth performance, carcass characteristics, and methane and CO2 emissions of growing and finishing cattle raised in extensive or partial-intensive cow-calf production systems

An experiment was conducted over 2 yr to measure performance and greenhouse gas (GHG) emissions of weaned calves from two cow-calf production systems. Crossbred steers and heifers (n = 270, initial body weight (BW) = 207 kg, SD = 35) were used in a randomized complete block design, with treatments applied to the cow-calf system. Treatments were: 1) a traditional system consisting of April to June calving with smooth bromegrass pasture and grazed corn residue as forage resources (TRAD); 2) an alternative system consisting of July to September calving utilizing partial-drylot feeding, summer-planted oats, and corn residue grazing (ALT). Calves from both production systems were weaned at the same age and grown (diet NEg = 1.05 Mcal kg-1) for approximately 117 d. The calves then transitioned to a high-grain finishing diet (year 1: NEg = 1.32 Mcal kg-1; year 2: NEg = 1.39 Mcal kg-1) and fed to a targeted 1.52 cm backfat. Growth performance in the grower phase resulted in greater (P < 0.01) average daily gain (1.39 vs. 1.22 ± 0.02 kg), greater gain:feed (P < 0.01; 0.157 vs. 0.137 ± 0.003) for ALT calves compared to TRAD calves, However, a lower initial BW (P < 0.01; 185 vs. 229 ± 4.9 kg) resulted in a lower ending BW (P < 0.01; 347 vs. 371 ± 2.9 kg) for ALT calves compared to TRAD calves in spite of improved growth performance. In the finisher phase, ALT calves gained less (1.52 vs. 1.81 ± 0.218 kg; P = 0.02), were less efficient (0.139 vs. 173 ± 0.0151; P = 0.01) but exhibited similar hot carcass weights (HCW) (388 vs. 381 ± 3.8 kg; P = 0.14) compared to TRAD calves. Each pen of calves was put into a large pen-scale chamber that continuously measured carbon dioxide (CO2) and methane (CH4) for 5 d during the grower and finisher phases. The average CH4 and CO2 production per unit of feed intake was used to calculate total GHG emissions over the entire grower and finisher phase. Overall, there were no differences (P ≥ 0.17) between treatments for CH4 per day and per kilogram dry matter intake (DMI). However, ALT calves tended to produce less (P ≤ 0.10) CO2 per day and per kilogram DMI than TRAD calves. Overall, methane emissions were greater in ALT calves (110.7 vs. 92.2 ± 8.3 g CH4 kg-1 HCW; P = 0.04) than TRAD calves. The ALT calves required 27 additional days on feed to market, which resulted in more total CH4 per animal across the entire feeding period (P = 0.02) than TRAD calves. Production systems that reduce days to market to achieve similar HCW may reduce GHG emissions.

Anabolic implants alter abundance of mRNA involved in muscle growth, metabolism, and inflammation in the longissimus of Angus steers in the feedlot

The majority of beef cattle in the United States often receive at least one anabolic implant resulting in improved growth, feed efficiency, and environmental and economic sustainability. However, the physiological and molecular mechanisms through which anabolic implants increase skeletal muscle growth of beef cattle remain elusive. The objective of this study was to identify transcriptional changes occurring in skeletal muscle of steers receiving anabolic implants containing different steroid hormones. Forty-eight steers were stratified by weight into 1 of 4 (n = 12/treatment) implant treatment groups: (1) estradiol (ImpE2; 25.7 mg E2; Compudose, Elanco Animal Health, Greenfield, IN), (2) trenbolone acetate (ImpTBA; 200 mg TBA; Finaplix-H, Merck Animal Health, Madison, NJ), (3) combination (ImpETBA; 120 mg TBA + 24 mg E2; Revalor-S, Merck Animal Health), or (4) no implant (CON). Skeletal muscle biopsies were taken from the longissimus 2 and 10 d post-implantation. The mRNA abundance of 94 genes associated with skeletal muscle growth was examined. At 10 d post-implantation, steers receiving ImpETBA had greater (P = 0.02) myoblast differentiation factor 1 transcript abundance than CON. Citrate synthase abundance was increased (P = 0.04) in ImpETBA steers compared to CON steers. In ImpE2 steers 10 d post-implantation, muscle RING finger protein 1 decreased (P = 0.05) compared to CON steers, and forkhead box protein O4 decreased (P = 0.05) in ImpETBA steers compared to CON steers. Interleukin-6 abundance tended to be increased (P = 0.09) in ImpE2 steers compared to both ImpETBA and CON steers. Furthermore, interleukin-10 mRNA abundance tended to be increased (P = 0.06) in ImpTBA steers compared to ImpETBA steers. Leptin receptor abundance was reduced (P = 0.01) in both ImpE2 and ImpTBA steers when compared to CON steers. Abundance of phosphodiesterase 4B was increased (P = 0.04) in ImpTBA steers compared to CON steers 2 d post-implantation. Taken together, the results of this research demonstrate that estradiol increases skeletal muscle growth via pathways related to nutrient partitioning and mitochondria function, while trenbolone acetate improves steer skeletal muscle growth via pathways related to muscle growth.

Environmental performance of commercial beef production systems utilizing conventional productivity-enhancing technologies

The objective of this study was to evaluate the effects of using conventional productivity-enhancing technologies (PETs) with or without other natural PETs on the growth performance, carcass traits and environmental impacts of feedlot cattle. A total of 768 cross-bred yearling steers (499 ± 28.6 kg; n = 384) and heifers (390 ± 34.9 kg; n = 384) were offered a barley grain-based basal diet and divided into implanted or non-implanted groups. Steers were then allocated to diets that contained either: (i) no additive (control); natural feed additives including (ii) fibrolytic enzymes (Enz), (iii) essential oil (Oleo), (iv) direct fed microbial (DFM), (v) DFM + Enz + Oleo combination; conventional feed additives including (vi) Conv (monensin, tylosin, and beta-adrenergic agonists [βAA]); or Conv with the natural feed additives including (vii) Conv + DFM + Enz; (viii) Conv + DFM + Enz + Oleo. Heifers received one of the first three dietary treatments or the following: (iv) probiotic (Citr); (v) Oleo + Citr; (vi) Melengesterol acetate (MGA) + Oleo + βAA; (vii) Conv (monensin, tylosine, βAA, and MGA); or (viii) Conv + Oleo (ConvOleo). Data were used to estimate greenhouse gas (GHG) and ammonia (NH3) emissions, as well as land and water use. Implant and Conv-treated cattle exhibited improvements in growth and carcass traits as compared to the other treatments (P &lt; 0.05). Improvements in the performance of Conv-cattle illustrated that replacing conventional feed additives with natural feed additives would increase both the land and water required to satisfy the feed demand of steers and heifers by 7.9% and 10.5%, respectively. Further, GHG emission intensity for steers and heifers increased by 5.8% and 6.7%, and NH3 emission intensity by 4.3% and 6.7%, respectively. Eliminating the use of implants in cattle increased both land and water use by 14.6% and 19.5%, GHG emission intensity by 10.5% and 15.8%, and NH3 emission intensity by 3.4% and 11.0% for heifers and steers, respectively. These results demonstrate that use of conventional PETs increased animal performance while reducing environmental impacts of beef production. Restricting use would increase the environmental footprint of beef produced for both domestic and international markets.

Effects of Yucca schidigera Based Feed Additive on In Vitro Dry Matter Digestibility, Efficiency of Microbial Production, and Greenhouse Gas Emissions of Four Dairy Diets

The present study evaluated the effects of a feed additive (synthesized from Yucca schidigera) on some fermentation variables. In the first of two experiments, seven concentrations of the feed additive were evaluated using the in vitro batch culture technique to determine the optimum dose to use in the second experiment. The substrates used were a total mixed ration (TMR) and alfalfa hay. The levels of inclusion were 0 (control), 0.5, 1, 2, 4, 6, and 8 g/head/d. After this initial evaluation, 2 g/head/d was selected for the second experiment. For the second study, four dietary substrates (two corn silages and two TMR; collected from different dairy farms in the Piedmont, North Carolina, area) were used. Incubation times were 3, 6, and 24 h and treatments were 0 (control) and 2 g/head/d of the feed additive. Inclusion of the feed additive did not affect (p > 0.05) in vitro dry matter disappearance. Additionally, the feed additive had no effect (p > 0.05) on short-chain fatty acid concentrations, microbial mass, and efficiency of microbial production. Methane production was reduced by 22.7% with feed additive inclusion. Similarly, lower (p = 0.013; 18%) carbon dioxide concentration was observed in the feed additive treatment. Ammonia and hydrogen sulfite concentrations were similar (p > 0.05) for both treatments. Inclusion of the feed additive at 2 g/head/d decreased methane and carbon dioxide concentrations in most of the diets. The energy saved by reducing the amount of methane produced was not partitioned into valuable products such as short-chain fatty acids and microbial mass.

Effect of trenbolone acetate, melengestrol acetate, and ractopamine hydrochloride on the growth performance of beef cattle

The effect of trenbolone acetate + estradiol (TBA) implants, melengestrol acetate (MGA), and ractopamine hydrochloride + TBA (RAC + TBA) on growth performance and carcass characteristics in beef cattle (n = 680; 279 ± 10.1 kg) fed barley grain/corn silage was examined in a 4 yr study (four pens per treatment per year; 262 ± 8 d feeding period). In the first 2 yr, treatments were (1) control heifers (H-CON; no growth promoters), (2) TBA-implanted heifers (H-TBA), (3) MGA heifers (H-MGA), (4) control steers (S-CON; no growth promoters), and (5) TBA-implanted steers (S-TBA). A sixth treatment (6) RAC + TBA steers (RAC + TBA) was included in years 3 and 4. Overall dry matter intake (DMI) of heifers was increased (P < 0.001) by TBA but not MGA. Compared with H-CONs, H-TBA had greater average daily gain (ADG) (P < 0.001), gain to feed ratio (G/F) (P < 0.001), and carcass weight (P < 0.001), whereas S-TBA had increased ADG (P < 0.001), G/F (P< 0.001), and carcass weight (P < 0.001) compared with S-CON. Compared with H-CON, H-MGA had increased (P < 0.01) ADG, G/F, and carcass weight. The RAC + TBA had increased (P < 0.01) ADG and carcass weight (3.2%) but not G/F or DMI compared with S-TBA. This 4 yr study showed a consistent positive impact of growth-enhancing technologies on the performance of Canadian feedlot cattle.

The role of livestock in sustainable food production systems in Canada

Global drivers such as the growing human population, evolving consumer preferences, globalization, and climate change have put pressure on the agri-food sector to produce more livestock products with less land, feed, and water. Taste, nutritional value, cost, convenience, source, animal welfare, and environmental sustainability of food are criteria upon which purchasing decisions are made. In response, an environmental footprint analysis composed of greenhouse gas emissions, nutrient and water use efficiency, water quality, carbon storage, and biodiversity has been completed for many commodities. However, as livestock production systems occur within complex agro-ecosystems, it is extremely challenging to formulate a single overall sustainability metric. There is no “silver bullet” to solve the environmental concerns of all livestock production systems as they operate under different constraints on different landscapes, with different water and nutrient cycles, and soil types. Furthermore, the lack of scientific evidence regarding the interactions between livestock production, human nutritional adequacy, and the health of our environment makes it difficult for consumers to interpret this information and make informed food choices. This review examines these complex interactions and trade-offs, as well as the potential impacts of changes in consumer dietary choice on environmental sustainability, nutritional adequacy, and land use.

Modeling the effects of steroid implant use on the environmental and economic sustainability of Brazilian beef production

Brazilian beef systems contribute 14.9% of global beef production, therefore given climate change concerns, there is a clear need to reduce environmental impacts while maintaining economic viability. This study evaluated the hypothesis that steroid implant use in Brazilian beef cattle would reduce resource use, greenhouse gas (GHG) emissions and economic costs of production, thereby improving environmental and economic sustainability. A deterministic model based on beef cattle population demographics, nutrition and performance was used to quantify resource inputs and GHG emissions per 1.0 × 106 kg of hot carcass weight (HCW) beef. System boundaries extended from cropping input manufacture to cattle arriving at the slaughterhouse. Beef systems were modeled using herd population dynamics, feed and performance data sourced from producers in four Brazilian states, with additional data from global databases. Implants were used in calves, growing and finishing cattle at low (LI), medium (MI), and high (HI) levels of performance enhancement, compared to nonimplanted (NI) controls. Feed use results were used in combination with producer-derived input costs to assess the economic impacts of implant use, including production costs and returns on investment. Improved FCE, ADG, and carcass weights conferred by implant use reduced the number of cattle and the time taken to produce 1.0 × 106 kg HCW beef. Compared to NI controls, the quantities of feed, land, water and fossil fuels required to produce 1.0 × 106 kg HCW beef was reduced in implanted cattle, with reductions proportional to the performance-enhancing effect of the implant (HI > MI > LI). Implant use reduced GHG emissions per 1.0 × 106 kg HCW beef by 9.4% (LI), 12.6% (MI), or 15.8% (HI). Scaling up the MI effects to represent all eligible Brazilian cattle being implanted, revealed avoided GHG emissions equivalent to the annual exhaust emissions of 62.0 × 106 cars. Economic impacts of implant use reflected the environmental results, resulting in a greater margin for the producers within each system (cow-calf through to finishing). The 6.13% increase in kg of HCW beef produced generates a cost reduction of 3.76% and an increase in the return on invested capital of 4.14% on average. Implants offer the opportunity for Brazilian beef producers to demonstrate their dedication to improving environmental and economic sustainability through improved productivity, although care must be taken to avoid negative trade-offs.

Anabolic Implants Varying in Hormone Type and Concentration Influence Performance, Feeding Behavior, Carcass Characteristics, Plasma Trace Mineral Concentrations, and Liver Trace Mineral Concentrations of Angus Sired Steers

Simple Summary

Though anabolic implants are commonly utilized in U.S. cattle production, comparisons between hormone type and content of different implants and the effects on growth and trace mineral stores is limited. The objective of this study was to evaluate the effects of anabolic implants varying in hormone type and concentration on growth, carcass characteristics, and trace mineral concentrations in Angus steers. Cattle administered an estradiol only implant did not experience differences in growth compared to non-implanted controls. However, cattle implanted with a trenbolone acetate only implant or a combined (estradiol and trenbolone acetate) implant experienced improvements in growth and changes in plasma and liver trace mineral concentrations. Greatest differences in growth and trace mineral concentrations were observed in steers administered the combination implant compared to non-implanted controls. These data suggest hormone type and concentration influence implant-induced growth and changes in plasma and liver trace mineral concentrations.

Abstract

Fifty Angus-sired steers were utilized to evaluate the effects of anabolic implants varying in hormone type and concentration on performance, carcass traits, and plasma and liver trace mineral concentrations over 129 d. Steers were stratified by weight into one of four (n = 12 or 13/treatment) implant treatments: (1) estradiol (E2; 25.7 mg E2; Compudose, Elanco Animal Health, Greenfield, IN, USA), (2) trenbolone acetate (TBA; 200 mg TBA; Finaplix-H, Merck Animal Health, Madison, NJ, USA), (3) combination implant (ETBA; 120 mg TBA + 24 mg E2; Revalor-S, Merck Animal Health), or (4) no implant (CON). Steers were randomly assigned to pens equipped with GrowSafe bunks and fed a corn and barley-based finishing ration. Overall average daily gain and body weight were greater for ETBA and TBA than CON (p ≤ 0.04), but not E2 (p ≥ 0.12). Feed efficiency and hot carcass weight were only greater than CON for ETBA (p ≤ 0.03). Plasma and d 2 liver Zn concentrations were lesser for ETBA than CON (p ≤ 0.01) and d 10 liver Mn was lesser (p = 0.0003) for TBA than CON. These data indicate that implants containing TBA influence growth and trace mineral parameters, though more work investigating this relationship is necessary.

Evaluation of Feed Strategies and Changes of Stocking Rate to Decrease the Carbon Footprint in a Traditional Cow-Calf System: A Simulation Model

One of the main production challenges associated with climate change is the reduction of carbon emissions. Increasing the efficiency of resource utilization is one way to achieve this purpose. The modification of production systems through improved reproductive, genetic, feed, and grazing management practices has been proposed to increase technical–economic efficiency, even though the “environmental viability” of these modifications has not always been evaluated. The objective of this study was to evaluate the use of feeding and management strategies on the carbon footprint (CF) and economic variables in the traditional cow–calf system in southern Chile using a simulation model. The modifications evaluated corresponded to combinations of stocking rate, use of creep feeding practices with different supplementation levels, and the incorporation of feed additives to the supplement, using factorial experiments. Additionally, the scenarios were evaluated with and without carbon sequestration. The CF for the baseline scenarios was 12.5 ± 0.3 kg of CO_2−eq/kg of live weight (LW) when carbon sequestration was considered and 13.0 ± 0.4 kg of CO_2−eq/kg of LW in the opposite case. Changes in stocking rate, supplementation level, and consideration of carbon sequestration in pasture and soil had a significant effect on the CF in all simulated scenarios. The inclusion of additives in the supplement did not have a significant effect on production costs. With regard to reducing greenhouse gas (GHG) emissions, incorporating canola oil presented the best average results. The model developed made the selection of environmentally viable feed strategies or management adaptations possible.

Beef cattle production impacts soil organic carbon storage

Grazing of natural rangeland and seeded pasture is an important feeding strategy for the Canadian beef cattle industry. As a consequence, beef cattle population has a direct influence on the proportion of land base maintained as perennial forage, which in turn changes soil organic carbon (SOC) stocks. We examined historical relationships between the net change in SOC resulting from perennial/annual crop conversion and beef cattle populations. We observed strong negative linear relationships, both regionally and nationally, between the population of beef cattle and the estimated change in SOC (negative sign indicating soil C sink) resulting from the conversion of annual crops and vice versa. These relationships indicate that as beef cattle population declines there is a corresponding loss of SOC resulting from a reduction in the relative proportion of perennial to annual crops on the landscape. The annual C loss resulting from land use conversion was roughly equivalent to 62% (±13%) of the combined enteric and manure annual emissions of CH₄ and N₂O [(1400 (±440) kg CO₂ eq head^-1 yr^-1] resulting in net greenhouse gas emissions of 850 (±360) kg CO₂ eq head^-1 yr^-1. These results highlight the importance of an integrated analysis that considers land use conversion and its impact on SOC when assessing the environmental footprint associated with beef cattle production.

Availability of disaggregated greenhouse gas emissions from beef cattle production: a systematic review

Agriculture is a significant source of anthropogenic greenhouse gas (GHG) emissions, and beef cattle are particularly emissions intensive. GHG emissions are typically expressed as a carbon dioxide equivalent (CO2e) 'carbon footprint' per unit output. The 100-year Global Warming Potential (GWP100) is the most commonly used CO2e metric, but others have also been proposed, and there is no universal reason to prefer GWP100 over alternative metrics. The weightings assigned to non-CO2 GHGs can differ significantly depending on the metric used, and relying upon a single metric can obscure important differences in the climate impacts of different GHGs. This loss of detail is especially relevant to beef production systems, as the majority of GHG emissions (as conventionally reported) are in the form of methane (CH4) and nitrous oxide (N2O), rather than CO2. This paper presents a systematic literature review of harmonised cradle to farm-gate beef carbon footprints from bottom-up studies on individual or representative systems, collecting the emissions data for each separate GHG, rather than a single CO2e value. Disaggregated GHG emissions could not be obtained for the majority of studies, highlighting the loss of information resulting from the standard reporting of total GWP100 CO2e alone. Where individual GHG compositions were available, significant variation was found for all gases. A comparison of grass fed and non-grass fed beef production systems was used to illustrate dynamics that are not sufficiently captured through a single CO2e footprint. Few clear trends emerged between the two dietary groups, but there was a non-significant indication that under GWP100 non-grass fed systems generally appear more emissions efficient, but under an alternative metric, the 100-year global temperature potential (GTP100), grass-fed beef had lower footprints. Despite recent focus on agricultural emissions, this review concludes there are insufficient data available to fully address important questions regarding the climate impacts of agricultural production, and calls for researchers to include separate GHG emissions in addition to aggregated CO2e footprints.

Effect of changes in management practices and animal performance on ammonia emissions from Canadian beef production in 1981 as compared with 2011

The present study compared ammonia (NH3) emissions from Canadian beef production in 1981–2011. Temporal and regional differences in cattle categories, feed types and management systems, average daily gains, carcass weights, and manure handling practices were considered. A scenario-based sensitivity analysis in 2011 estimated the impact of substituting corn dried distillers’ grains with solubles (DDGS) for grain in feedlot diets. On average, 22% of the total nitrogen (N) intake was lost as ammoniacal nitrogen (NH3-N) in both years. Manure emission sources were consistent across years, averaging 12%, 40%, 28%, and 21% for grazing, confinement, storage, and land spreading, respectively. Emissions per animal in 1981 and 2011 were 16.0 and 18.4 kg NH3 animal−1 yr−1, respectively. On an intensity basis, kilogram of NH3 emitted per kilogram of beef decreased 20%, from 0.17 in 1981 to 0.14 in 2011. This reduction was attributed to increases in reproductive efficiency, average daily gain and carcass weight, and improved breeding herd productivity. In 2011, substituting DDGS for grain in feedlot diets increased total NH3 emissions and losses per animal. Although addition of by-products from the bioethanol industry can lower diet costs, it will be at the expense of an increase in NH3 emissions.

Genomic retained heterosis effects on fertility and lifetime productivity in beef heifers

This study evaluated the effects of three genomic indicators of heterosis on female fertility and lifetime productivity, and quantified changes over 11 production cycles in a crossbred cow herd. Pedigree-based breed composition (pBC) was determined and used to calculate retained heterozygosity for 412 replacement heifers born from 2004 to 2014 at the Lacombe Research and Development Centre (AB, Canada). Heifers were followed as cows over 1050 mating opportunities, 11 production cycles, and five parities. Heifers and their sires (51) were genotyped and these genotypes were used to predict each animal’s genomic breed composition (gBC) and three genomic indicators of heterosis: (1) retained heterozygosity (RHETg), (2) heterozygous proportion (H), and (3) retained heterosis (RHg). Correlations between pedigree and genomic breed fractions for Angus, Hereford, and Charolais were high (rp = 0.74–0.94; P < 0.001). Genomic indicators of heterosis were highly related (rp = 0.61 for RHETg vs. H; 0.71 for RHg vs. H; 0.96 for RHETg vs. RHg; P < 0.001). Each 10% change in RHETg resulted in 51 ± 20 d longer survival (P = 0.011) in the herd and 35.7 ± 15.2 kg more (P = 0.019) calf wean weight per cow exposed to breeding when summed over five parities. These differences resulted in an extra $161 per heifer in a year. Optimizing heterosis using genomic tools can be very beneficial for the cow herd if applied correctly.

Development and validation of a small SNP panel for feed efficiency in beef cattle

The objective of this study was to develop and validate a customized cost-effective single nucleotide polymorphism (SNP) panel for genetic improvement of feed efficiency in beef cattle. The SNPs identified in previous association studies and through extensive analysis of candidate genomic regions and genes, were screened for their functional impact and allele frequency in Angus and Hereford breeds used as validation candidates for the panel. Association analyses were performed on genotypes of 159 SNPs from new samples of Angus (n = 160), Hereford (n = 329), and Angus-Hereford crossbred (n = 382) cattle using allele substitution and genotypic models in ASReml. Genomic heritabilities were estimated for feed efficiency traits using the full set of SNPs, SNPs associated with at least one of the traits (at P ≤ 0.05 and P < 0.10), as well as the Illumina bovine 50K representing a widely used commercial genotyping panel. A total of 63 SNPs within 43 genes showed association (P ≤ 0.05) with at least one trait. The minor alleles of SNPs located in the GHR and CAST genes were associated with decreasing effects on residual feed intake (RFI) and/or RFI adjusted for backfat (RFIf), whereas minor alleles of SNPs within MKI67 gene were associated with increasing effects on RFI and RFIf. Additionally, the minor allele of rs137400016 SNP within CNTFR was associated with increasing average daily gain (ADG). The SNPs genotypes within UMPS, SMARCAL, CCSER1, and LMCD1 genes showed significant over-dominance effects whereas other SNPs located in SMARCAL1, ANXA2, CACNA1G, and PHYHIPL genes showed additive effects on RFI and RFIf. Gene enrichment analysis indicated that gland development, as well as ion and cation transport are important physiological mechanisms contributing to variation in feed efficiency traits. The study revealed the effect of the Jak-STAT signaling pathway on feed efficiency through the CNTFR, OSMR, and GHR genes. Genomic heritability using the 63 significant (P ≤ 0.05) SNPs was 0.09, 0.09, 0.13, 0.05, 0.05, and 0.07 for ADG, dry matter intake, midpoint metabolic weight, RFI, RFIf, and backfat, respectively. These SNPs contributed to genetic variation in the studied traits and thus can potentially be used or tested to generate cost-effective molecular breeding values for feed efficiency in beef cattle.

Water use intensity of Canadian beef production in 1981 as compared to 2011

The amount of beef produced per animal in Canada increased significantly from 1981 to 2011, due to enhanced production efficiency and increased carcass weight. This study examined the impact of improvements in production efficiency on water use intensity over this period. Temporal and regional differences in cattle categories, water use for drinking, feed production and meat processing, feeding systems, average daily gains, and carcass weight were considered in the analysis. Potential evapotranspiration (PET) was estimated by the National Drought Model (NDM) from 679 weather stations across Canada using the Priestley and Taylor equation. To adjust PET estimates for each crop included in cattle diets, FAO crop coefficients were used to calculate total feed water demand. Estimates of drinking water consumed by a given class of cattle accounted for physiological status, body weight and dry matter intake as well as ambient temperature. In both years, drinking water accounted for less than 1% of total water use with precipitation (i.e., green water) included for feed and pasture production. With exclusion of green water, drinking water accounted for 24% and 21% of total water use for Canadian beef production in 1981 and 2011, respectively. The estimated intensity of blue water (surface and groundwater) use per kilogram of boneless beef was 577L in 1981 and 459 in 2011, a 20% decline. The observed reduction in water use intensity over the past three decades is attributed to an increase in average daily gain and slaughter weight, improved reproductive efficiency, reduced time to slaughter as well as improvements in crop yields and irrigation efficiency. Given that feed production accounts for the majority of water use in beef production, further advances may be achieved by improving feeding efficiencies and reducing water use per unit of feed crop and pasture production.

Greenhouse gas emissions of Canadian beef production in 1981 as compared with 2011

The present study compared the greenhouse gas (GHG) emissions, and breeding herd and land requirements of Canadian beef production in 1981 and 2011. In the analysis, temporal and regional differences in feed types, feeding systems, cattle categories, average daily gains and carcass weights were considered. Emissions were estimated using life-cycle assessment (cradle to farm gate), based primarily on Holos, a Canadian whole-farm emissions model. In 2011, beef production in Canada required only 71% of the breeding herd (i.e. cows, bulls, calves and replacement heifers) and 76% of the land needed to produce the same amount of liveweight for slaughter as in 1981. Compared with 1981, in 2011 the same amount of slaughter weight was produced, with a 14% decline in CH4 emissions, 15% decline in N2O emissions and a 12% decline in CO2 emissions from fossil fuel use. Enteric CH4 production accounted for 73% of total GHG emissions in both years. The estimated intensity of GHG emissions per kilogram of liveweight that left the farm was 14.0 kg CO2 equivalents for 1981 and 12.0 kg CO2 equivalents for 2011, a decline of 14%. A significant reduction in GHG intensity over the past three decades occurred as a result of increased average daily gain and slaughter weight, improved reproductive efficiency, reduced time to slaughter, increased crop yields and a shift towards high-grain diets that enabled cattle to be marketed at an earlier age. Future studies are necessary to examine the impact of beef production on other sustainability metrics, including water use, air quality, biodiversity and provision of ecosystems services.

Review: Canadian beef grading – Opportunities to identify carcass and meat quality traits valued by consumers

Aalhus, J. L., López-Campos, Ó., Prieto, N., Rodas-González, A., Dugan, M. E. R., Uttaro, B. and Juárez, M. 2014. Review: Canadian beef grading – Opportunities to identify carcass and meat quality traits valued by consumers. Can. J. Anim. Sci. 94: 545–556. Beef value is in the eye, mouth or mind of the consumer; however, currently, producers are paid on the basis of carcass grade. In general, affluent consumers are becoming more discerning and are willing to pay for both credence and measureable quality differences. The Canadian grading system for youthful carcasses identifies both lean yield and quality attributes, whereas mature carcasses are broadly categorized. Opportunities exist to improve the prediction of lean meat yield and better identify meat quality characteristics in youthful beef, and to obtain additional value from mature carcasses through muscle profiling. Individual carcass identification along with development of database systems like the Beef InfoXchange System (BIXS) will allow a paradigm shift for the industry as traits of economic value can be easily identified to improve marketing value chains. In the near future, developing technologies (e.g., grade cameras, dual energy X-ray absorptiometry, and spectroscopic methods such as near infrared spectroscopy, Raman spectroscopy and hyperspectral imaging) will be successfully implemented on-line to identify a multitude of carcass and quality traits of growing importance to segments of the consuming population.

Genetic parameters for predicted methane production and laser methane detector measurements

Enteric ruminant methane is the most important greenhouse gas emitted from the pastoral agricultural systems. Genetic improvement of livestock provides a cumulative and permanent impact on performance, and using high-density SNP panels can increase the speed of improvement for most traits. In this study, a data set of 1,726 dairy cows, collected since 1990, was used to calculate a predicted methane emission (PME) trait from feed and energy intake and requirements based on milk yield, live weight, feed intake, and condition score data. Repeated measurements from laser methane detector (LMD) data were also available from 57 cows. The estimated heritabilities for PME, milk yield, DMI, live weight, condition score, and LMD data were 0.13, 0.25, 0.11, 0.92, 0.38, and 0.05, respectively. There was a high genetic correlation between DMI and PME. No SNP reached the Bonferroni significance threshold for the PME traits. One SNP was within the 3 best SNP for PME at wk 10, 20, 30, and 40. Genomic prediction accuracies between dependent variable and molecular breeding value ranged between 0.26 and 0.30. These results are encouraging; however, more work is required before a PME trait can be implemented in a breeding program.

Subcutaneous fatty acid composition of steers finished as weanlings or yearlings with and without growth promotants

BACKGROUND

The current study evaluated the subcutaneous fatty acid (FA) composition of calf- and yearling-fed steers with or without growth promoting implants. Crossbred steers (n = 112; 267 ± 5.0 kg) of the same contemporary group were allocated to one of four production system and implant strategy based treatments in a completely randomized design with a 2 × 2 factorial arrangement of treatments.

RESULTS

There were no interactions (P > 0.05) between production systems and growth promoting implants for the total and individual subcutaneous FA. Yearling as opposed to calf finishing reduced (P < 0.05) subcutaneous proportions of C20:3n-6, trans (t)12-18:1, C14:0, several minor cis-monounsaturated FA (c-MUFA; c9-14:1, c11-16:1, c11-18:1, c12-18:1, c13-18:1, c9-20:1 and c11-20:1), and increased (P < 0 .05) subcutaneous proportions of t11c15-18:2, total and individual branched-chain FA. Subcutaneous fat from steers implanted with growth promotants had higher (P < 0.05) proportions of total polyunsaturated FA (PUFA), total n-6 PUFA, C18:2n-6 and individual t-18:1 isomers (t6 to t10) compared to non-implanted steers.

CONCLUSIONS

Overall, current findings show that production systems and growth promotants led to only minor differences in subcutaneous FA composition of beef steers.

Livestock and the promise of genomics

The emergence of the middle class in countries such as Brazil, Russia, India, and China is resulting in increasing global demand for animal-based food products. This increase represents a unique opportunity for Canadian livestock producers to export their products to new markets and expand Canada's reputation as a global provider of safe and highest quality food items. This article has two major themes. First, current Canadian contributions to livestock genomics in the cattle and swine industries are outlined. Second, important future opportunities are discussed, including the high throughput collection of phenotypic data, development of environmentally friendly livestock, emergence of decision support software, and the use of Web 2.0. Through the use of genomic technologies, livestock producers can not only ensure that the nutritional demands of Canada are secured, but also play a pivotal role in ensuring the rest of the world is fed as well. Furthermore, investment through initiatives led by Genome Canada has ensured that Canada is favorably positioned to contribute cutting-edge solutions to meet this global challenge. Ultimately, genomic-based innovations will enable producers to increase efficiency, lower production costs, decrease the use of prophylactics, and limit the expenditure of resources.

Reducing GHG emissions through genetic improvement for feed efficiency: effects on economically important traits and enteric methane production

Genetic selection for residual feed intake (RFI) is an indirect approach for reducing enteric methane (CH4) emissions in beef and dairy cattle. RFI is moderately heritable (0.26 to 0.43), moderately repeatable across diets (0.33 to 0.67) and independent of body size and production, and when adjusted for off-test ultrasound backfat thickness (RFI fat) is also independent of body fatness in growing animals. It is highly dependent on accurate measurement of individual animal feed intake. Within-animal repeatability of feed intake is moderate (0.29 to 0.49) with distinctive diurnal patterns associated with cattle type, diet and genotype, necessitating the recording of feed intake for at least 35 days. In addition, direct measurement of enteric CH4 production will likely be more variable and expensive than measuring feed intake and if conducted should be expressed as CH4 production (g/animal per day) adjusted for body size, growth, body composition and dry matter intake (DMI) or as residual CH4 production. A further disadvantage of a direct CH4 phenotype is that the relationships of enteric CH4 production on other economically important traits are largely unknown. Selection for low RFI fat (efficient, -RFI fat) will result in cattle that consume less dry matter (DMI) and have an improved feed conversion ratio (FCR) compared with high RFI fat cattle (inefficient; +RFI fat). Few antagonistic effects have been reported for the relationships of RFI fat on carcass and meat quality, fertility, cow lifetime productivity and adaptability to stress or extensive grazing conditions. Low RFI fat cattle also produce 15% to 25% less enteric CH4 than +RFI fat cattle, since DMI is positively related to enteric methane (CH4) production. In addition, lower DMI and feeding duration and frequency, and a different rumen bacterial profile that improves rumen fermentation in -RFI fat cattle may favor a 1% to 2% improvement in dry matter and CP digestibility compared with +RFI fat cattle. Rate of genetic change using this approach is expected to improve feed efficiency and reduce enteric CH4 emissions from cattle by 0.75% to 1.0% per year at equal levels of body size, growth and body fatness compared with cattle not selected for RFI fat.

A Greenhouse Gas and Soil Carbon Model for Estimating the Carbon Footprint of Livestock Production in Canada

To assess tradeoffs between environmental sustainability and changes in food production on agricultural land in Canada the Unified Livestock Industry and Crop Emissions Estimation System (ULICEES) was developed. It incorporates four livestock specific GHG assessments in a single model. To demonstrate the application of ULICEES, 10% of beef cattle protein production was assumed to be displaced with an equivalent amount of pork protein. Without accounting for the loss of soil carbon, this 10% shift reduced GHG emissions by 2.5 TgCO₂e y(-1). The payback period was defined as the number of years required for a GHG reduction to equal soil carbon lost from the associated land use shift. A payback period that is shorter than 40 years represents a net long term decrease in GHG emissions. Displacing beef cattle with hogs resulted in a surplus area of forage. When this residual land was left in ungrazed perennial forage, the payback periods were less than 4 years and when it was reseeded to annual crops, they were equal to or less than 40 years. They were generally greater than 40 years when this land was used to raise cattle. Agricultural GHG mitigation policies will inevitably involve a trade-off between production, land use and GHG emission reduction. ULICEES is a model that can objectively assess these trade-offs for Canadian agriculture.