Accounting for uncertainty in the quantification of the environmental impacts of Canadian pig farming systems

Indigenous food production in a carbon economy

Indigenous communities in the North American Arctic are characterized by mixed economies that feature hunting, fishing, gathering, and trapping activities-and associated sharing practices-alongside the formal wage economy. The region is also undergoing rapid social, economic, and climate changes, including, in Canada, carbon taxation, which is impacting the cost of fuel used in local food harvesting. Because of the importance of local foods to nutrition, health, and well-being in Arctic Indigenous communities, there is an urgent need to better understand the sensitivity of Arctic food systems to social, economic, and climate changes and to develop plans for mitigating potential adverse effects. Here, we develop a Bayesian model to calculate the substitution value and carbon emissions of market replacements for local food harvests in the Inuvialuit Settlement Region, Canada. Our estimates suggest that under plausible scenarios, replacing locally harvested foods with imported market substitutes would cost over 3.1 million Canadian dollars per year and emit over 1,000 tons of CO2-equivalent emissions per year, regardless of the shipping scenario. In contrast, we estimate that gasoline inputs to harvesting cost approximately $295,000 and result in 315 to 497 tons of emissions. These results indicate that climate change policies that fail to account for local food production may undermine emissions targets and adversely impact food security and health in Arctic Indigenous communities, who already experience a high cost of living and high rates of food insecurity.

The impact of slaughter weight and sex on the carbon footprint of pig feed intake

The impact of pork production on global livestock's greenhouse gas emissions is substantial. Understanding the factors influencing these emissions is crucial in achieving a more sustainable pig husbandry. In two independent experiments, the impact of slaughter weight on the carbon footprint (CFP) of pig feed intake (CFPFI) was evaluated for growing-finishing pigs of different sexes (entire males (EM), barrows (BA), immunocastrates (IC) and gilts (GI)). In experiment 1 118 animals were raised individually in experimental conditions. In experiment 2 384 animals were housed in group (four pigs per pen), in controlled commercial farm circumstances. All animals were fed ad libitum in a three-phase feeding regime and slaughtered at different BW, ranging from 110 to 148 kg (experiment 1) and from 99 to 138 kg (experiment 2). When only the fattening period was considered, the CFPFI was expressed per kg carcass growth. When the production of piglets was also taken into account, the CFPFI was calculated per kg carcass weight. For all sexes, the heavier the pig, the higher the CFPFI per kg carcass growth (P < 0.05, experiment 1; P < 0.001, experiment 2) and per kg carcass weight (P < 0.05, experiment 1; P < 0.01, experiment 2). In addition, BA had a significantly higher CFPFI per kg carcass growth and per kg carcass weight compared to EM and IC and to EM, IC and GI in respectively experiments 1 and 2 (P < 0.001). When performing a desk study with a soy-free (i.e. reduced CFP) feed in the third phase of experiment 2, slaughter weight no longer affected the CFPFI per kg carcass growth (P = 0.133) and per kg carcass weight (P = 0.856). A higher slaughter weight thus implies a lower sustainability, unless a sufficiently low-CFP feed is provided in the finisher phase.

A systematic review of life-cycle GHG emissions from intensive pig farming: Accounting and mitigation

Pork accounts for approximately 35 % of the global meat supply, with approximately 747 million tons of CO2e greenhouse gas (GHG) emissions annually. To meet the increasing demand for pork, intensive farming is becoming the priority rearing system owing to its higher productivity. Given the climate transformation ambitions of the pig industry but the lack of knowledge and data, we conducted a systematic review of studies published in the period of 2010-2022 from a life-cycle perspective, with a focus on greenhouse gas emissions accounting and mitigation. The significant variations in systematic harmonized global warming intensities (GWIs) can be primarily attributed to differences in accounting approaches, activity data, technologies and geographical conditions. To understand more, we broke down the entire life cycle and revealed the underlying reasons for modelling mechanisms and data from the main emitters (e.g., feeding, pig rearing, and manure management). These findings are expected to support and improve the transparency, consistency, and comprehensiveness of life-cycle GHG emissions accounting in pig farming. Potential mitigation measures were also reviewed and discussed to provide insights to support the sustainable development of the pig industry.

Environmental Impacts of Pig and Poultry Production: Insights From a Systematic Review

Pig and poultry production systems have reached high-performance levels over the last few decades. However, there is still room for improvement when it comes to their environmental sustainability. This issue is even more relevant due to the growing demand for food demand since this surplus food production needs to be met at an affordable cost with minimum impact on the environment. This study presents a systematic review of peer-reviewed manuscripts that investigated the environmental impacts associated with pig and poultry production. For this purpose, independent reviews were performed and two databases were constructed, one for each production system. Previous studies published in peer-reviewed journals were considered for the databases if the method of life cycle assessment (LCA) was applied to pig (pork meat) or poultry (broiler meat or table eggs) production to estimate at least the potential effects of climate change, measured as CO₂-eq. Studies considering the cradle-to-farm gate were considered, as well as those evaluating processes up to the slaughterhouse or processor gate. The pig database comprised 55 studies, while 30 publications were selected for the poultry database. These studies confirmed feeding (which includes the crop cultivation phase, manufacturing processes, and transportation) as the main contributor to the environmental impact associated with pig and poultry production systems. Several studies evaluated feeding strategies, which were indicated as viable alternatives to mitigate the environmental footprint associated with both production chains. In this study, precision feeding techniques are highlighted given their applicability to modern pig and poultry farming. These novel feeding strategies are good examples of innovative strategies needed to break paradigms, improve resource-use efficiency, and effectively move the current productive scenario toward more sustainable livestock systems.

Environmental Impacts Associated with Intensive Production in Pig Farms in Mexico through Life Cycle Assessment

In this research, environmental impacts associated with the intensive production of pigs on a farm in Mexico were determined through the application of life cycle assessment methodology. The research was focused on the following stages of the product system: (i) pig rearing and growth phases; (ii) production operations in the pig-house; (iii) the supply of feed. The life cycle inventory database was mainly made up of data collected in field visits to local farms. The functional unit was defined as one finished swine weighing 124 kg. The results for the selected impact categories of carbon, water, and energy footprints were 538.62 kg CO2eq, 21.34 m3, and 1773.79 MJ, respectively. The greatest impact was generated in the final stages of pig fattening, mainly due to the large quantity of feed supplied. The impacts caused by operation of the pig farm were less significant, their contribution in all cases was less than a third of the total quantified values. The energy conversion of pig slurry improves the environmental performance of the product system by reducing the carbon footprint.

Evaluating environmental impacts of selection for residual feed intake in pigs

To identify a proper strategy for future feed-efficient pig farming, it is required to evaluate the ongoing selection scenarios. Tools are lacking for the evaluation of pig selection scenarios in terms of environmental impacts to provide selection guidelines for a more sustainable pig production. Selection on residual feed intake (RFI) has been proposed to improve feed efficiency and potentially reduce the associated environmental impacts. The aim of this study was thus to develop a model to account for individual animal performance in life cycle assessment (LCA) methods to quantify the responses to selection. Experimental data were collected from the fifth generation of pig lines divergently selected for RFI (low line, more efficient pigs, LRFI; high line, less efficient pigs, HRFI). The average feed conversion ratio (FCR) and daily feed intake of LRFI pigs were 7% lower than the average of HRFI pigs (P < 0.0001). A parametric model was developed for LCA based on the dietary net energy fluxes in a pig system. A nutritional pig growth tool, InraPorc®, was included as a module in the model to embed flexibility for changes in feed composition, animal performance traits and housing conditions and to simulate individual pig performance. The comparative individual-based LCA showed that LRFI had an average of 7% lower environmental impacts per kilogram live pig at farm gate compared to HRFI (P < 0.0001) on climate change, acidification potential, freshwater eutrophication potential, land occupation and water depletion. High correlations between FCR and all environmental impact categories (>0.95) confirmed the importance of improvement in feed efficiency to reduce environmental impacts. Significant line differences in all impact categories and moderate correlations with impacts (>0.51) revealed that RFI is an effective measure to select for improved environmental impacts, despite lower correlations compared to FCR. Altogether more optimal criteria for efficient environment-friendly selection can then be expected through restructuring the selection indexes from an environmental point of view.

How do pigs deal with dietary phosphorus deficiency?

Feeding strategies for growing monogastric livestock (particularly pigs) must focus on maximising animal performance, while attempting to reduce environmental P load. Achieving these goals requires a comprehensive understanding of how different P feeding strategies affect animal responses and an ability to predict P retention. Although along with Ca, P is the most researched macromineral in pig nutrition, knowledge gaps still exist in relation to: (1) the effects of P feed content on feed intake (FI); (2) the impact of P intake on body composition; (3) the distribution of absorbed P to pools within the body. Here, we address these knowledge gaps by gathering empirical evidence on the effects of P-deficient feeds and by developing a predictive, mechanistic model of P utilisation and retention incorporating this evidence. Based on our statistical analyses of published literature data, we found: (1) no change in FI response in pigs given lower P feed contents; (2) the body ash–protein relationship to be dependent upon feed composition, with the isometric relationship only holding for pigs given balanced feeds and (3) the priority to be given towards P retention in soft tissue over P retention in bones. Subsequent results of the mechanistic model of P retention indicated that a potential reduction in P feeding recommendations could be possible without compromising average daily gain; however, such a reduction would impact P deposition in bones. Our study enhances our current knowledge of P utilisation and by extension excretion and could contribute towards developing more accurate P feeding guidelines.

Impact of the treatment of NH3 emissions from pig farms on greenhouse gas emissions. Quantitative assessment from the literature data

In order to limit ammonia (NH₃) emissions from pig farms, various air cleaning solutions are widely applied. However, the literature data report that these systems (chemical scrubbers, bioscrubbers and biofilters) can be both inefficient and promote nitrous oxide (N₂O) production. As air cleaning technologies should not contribute to secondary trace gases that may have a stronger environmental impact than the raw gas compounds themselves, the objective of this study was to quantify the effect of NH₃ treatment in pig farms on greenhouse gas (GHG) emissions. GHGs (carbon dioxide, methane and nitrous oxide) emitted at the outlet of three different cleaning systems ("chemical scrubber", "bioscrubber" and "bioscrubber + denitrification step") were assessed and compared with the emissions generated by the exhaust air with "no treatment". The calculations show that the chemical scrubber has no effect whereas biological treatments can increase GHG emissions. The use of bioscrubbers alone for NH₃ removal can remain acceptable provided that less than 3% of the NH₃ entering the apparatus is converted into N₂O. In such cases, a maximum increase of 1.9% in GHG emissions could be obtained. Conversely, the addition of a denitrification step to a bioscrubber must be avoided. Increases in overall GHG emissions of up to 25.8% were calculated but more significant increases could occur. With regard to GHG emissions, it is concluded that the use of a chemical scrubber is more suitable than a bioscrubber to treat exhaust air from pig farms.

Effect of Three Husbandry Systems on Environmental Impact of Organic Pigs

This study examined the environmental impact of the three common organic pig husbandry systems, indoor (n = 24), partly outdoor (n = 30), and outdoor (n = 10), in eight European countries. Global warming (GWP), acidification (AP), and eutrophication potential (EP) was assessed per 1000 kg pig live weight on 64 farrow-to-finish pig production chains (cradle to farm gate). GWP, AP, and EP varied greatly, and the most important source was feed production, followed by housing. GWP did not differ between systems (p = 0.934), but AP in indoor systems and EP in outdoor systems were higher than in partly outdoor systems (p = 0.006 and p = 0.010, respectively). The higher AP in indoor systems can mainly be explained by NH3 arising from manure spreading, while PO4-eq arising from feed consumption and emissions on pasture accounted for the higher EP in outdoor systems. Associations of farm characteristics with (reduced) environmental impacts were mainly found for AP and EP, and included: (Increasing) farm size, numbers of piglets born and weaned per litter, (bought-in) mineral feed, and high-protein by-products, the latter probably connected to beneficial effects of appropriate dietary digestible lysine levels and feed conversion ratio. Increasing carcass weights and dietary cereal proportions were associated with higher environmental impacts. Overall, variation was mostly higher within than between systems, and measures to mitigate environmental impact were identified.

Do not neglect calcium: a systematic review and meta-analysis (meta-regression) of its digestibility and utilisation in growing and finishing pigs

Ca digestibility and utilisation in growing pigs are not well understood, and are usually neglected in diet formulation. This has implications not only for the accurate determination of its requirements but also for its interactions with other nutrients. A systematic review and meta-analysis (meta-regression) of published trials was carried out to quantify factors affecting Ca absorption and utilisation, and to derive an estimate of Ca endogenous excretion. The analysis was carried out on the data from forty studies, corresponding to 201 treatments performed on 1204 pigs. The results indicated that although Ca absorption and retention (g/kg of body weight per d) increased with increasing Ca intake (P<0·001), non-phytate-P intake (P<0·001) and exogenous phytase supplementation (P<0·001), these values decreased with increasing phytate-P intake (P<0·05). Interactions between exogenous phytase and Ca intake, indicating reduced efficacy of this enzyme (P<0·001), and between phytate-P intake and exogenous phytase, counteracting the direct negative effect of phytate-P (P<0·05) on Ca absorption and retention, were also detected. There were no effects of animal-related characteristics, such as pig genotype in Ca absorption and retention. The large amount of variance explained in Ca absorption (90 %) and retention (91 %) supported our choice of independent variables. Endogenous Ca losses obtained via linear regression were 239 mg/kg of DM intake (95 % CI 114, 364). These outcomes advance the current understanding of Ca digestibility and utilisation, and should contribute towards establishing requirements for digestible Ca. Consequently, pig diets will be more correctly formulated if digestible Ca values are used in estimating requirements for Ca.

Environmental impact of using specialty feed ingredients in swine and poultry production: A life cycle assessment

Livestock production has a variety of environmental impacts such as greenhouse gas emissions, water pollution, acidification, and primary energy consumption. The demand for livestock products is expected to grow substantially, creating even more environmental pressure. The use of specialty feed ingredients (SFI) such as supplemented AA and phytase can reduce nutrient input into the system without compromising productivity and consequently can reduce emissions. The global change impact of using SFI in pig and broiler production systems in Europe and North and South America was studied. A life cycle assessment according to international standards (ISO 14040/44) analyzed contributions from producing SFI and animals to global change. Three different alternatives were analyzed. In addition, partial sensitivity analysis was conducted using 5 scenarios for each region for both production systems. Specialty feed ingredient supplementation in pig and broiler diets reduced greenhouse gas emissions (cradle to farm gate) by 56% and 54% in Europe, 17% and 15% in North America, and 33% and 19% in South America, respectively, compared to an unsupplemented diet. A total of 136 Mt CO equivalent (CO eq) was saved in 2012, rising to 146 Mt CO eq in 2050 on the basis of United Nations population projections. Considerable benefits of supplementation with SFI were apparent in European and South American diets when direct land use change was considered because of the reduced demand for soybean meal. The eutrophication potential of unsupplemented diets was reduced by up to 35% in pig and 49% in broiler production systems compared to supplemented alternatives. The acidification potential of supplemented strategies was reduced by up to 30% in pig and 79% in broiler production systems. The primary energy demand was similar in all alternatives, and this could be an area where the SFI industry can improve. Overall, SFI supplementation substantially reduced the global warming, eutrophication, and acidification potentials in all regions studied.

Towards a methodology to formulate sustainable diets for livestock: accounting for environmental impact in diet formulation

The objective of this study was to develop a novel methodology that enables pig diets to be formulated explicitly for environmental impact objectives using a Life Cycle Assessment (LCA) approach. To achieve this, the following methodological issues had to be addressed: (1) account for environmental impacts caused by both ingredient choice and nutrient excretion, (2) formulate diets for multiple environmental impact objectives and (3) allow flexibility to identify the optimal nutritional composition for each environmental impact objective. An LCA model based on Canadian pig farms was integrated into a diet formulation tool to compare the use of different ingredients in Eastern and Western Canada. By allowing the feed energy content to vary, it was possible to identify the optimum energy density for different environmental impact objectives, while accounting for the expected effect of energy density on feed intake. A least-cost diet was compared with diets formulated to minimise the following objectives: non-renewable resource use, acidification potential, eutrophication potential, global warming potential and a combined environmental impact score (using these four categories). The resulting environmental impacts were compared using parallel Monte Carlo simulations to account for shared uncertainty. When optimising diets to minimise a single environmental impact category, reductions in the said category were observed in all cases. However, this was at the expense of increasing the impact in other categories and higher dietary costs. The methodology can identify nutritional strategies to minimise environmental impacts, such as increasing the nutritional density of the diets, compared with the least-cost formulation.