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.

Soybean Replacement by Alternative Protein Sources in Pig Nutrition and Its Effect on Meat Quality

Soybean is one of the most expensive and limiting feed ingredients in diet formulations; however, in pig farming, it represents the main source of protein. The production and supply of soybean are critical steps due to their environmental impact and feed/food competition for land use. Therefore, research is focusing on finding alternatives to replace soybean partially or totally. However, alternative ingredients should ensure similar growth performance, carcass traits, and meat quality characteristics compared to conventional soybean-based diets. The objective of this review was to evaluate the impact of different alternative protein sources to soybean in pig nutrition and their effects on growth performance, carcass, and meat quality traits. The review process was performed on Scopus^®, and it considered research findings published from 2012 to the present on the Sus scrofa species. Articles without a control group fed with soybean were discarded. The main alternative protein sources identified were other legumes and distillers' dried grain with solubles (fish and animal proteins, oilseed by- and co-products). Interesting innovative protein sources included by-products from other industries (residues), microalgae and insects. Nevertheless, in dietary formulations, close attention must be paid to address the nutritional requirements, balance the supply of amino acids, avoid anti-nutritional or toxic compounds occasionally present in alternative protein sources, as well as determine the availability of protein feed in specific geographical areas.

Life Cycle Assessment Perspective for Sectoral Adaptation to Climate Change: Environmental Impact Assessment of Pig Production

Growing demand for sustainably driven production systems, especially pork, requires a holistic or system thinking approach. Life Cycle Thinking (LCT) offers a robust methodological background as one of the approaches to achieving system analysis for a product along its lifecycle. On the other hand, Life Cycle Assessment (LCA) can perform state-of-art system analysis characterising its sustainability fronts as a compelling set of tools. Pork, as the most consumed meat across Europe (circa 34 kg per capita per year), compounded with the sector’s contribution to global greenhouse gases (GHG) doubling over the past decade necessitated this research. Our objective was to map hotspots along the value chain and recommend the best available practices for realising the sectoral contribution to carbon neutrality and climate change adaptation. To achieve the objective, we compared organic and conventional production systems by basing our analysis on Recipe midpoint 2016 (H) V1.13 as implemented in OpenLCA 1.10.2 using AGRIBALYSE® 3.0 datasets for eleven indicators. We found that producing 1 kg of pig meat under an organic production system had almost double the environmental impact of conventional systems for land use, water consumption, acidification, and ecotoxicity. Feed production and manure management are the significant hotspots accounting for over 90% of environmental impacts associated with 1 kg pig meat Liveweight (LW) production. Similarly, efficient conventional systems were less harmful to the environment in per capita unit of production and land use compared with organic ones in ten out of the eleven impacts evaluated. Implementing increased efficiency, reduced use of inputs for feed production, and innovative manure management practices with technological potential were some of the best practices the research recommended to realise minimal impacts on the identified hotspots.

Environmental Sustainability Assessment of Pig Farms in Selected European Countries: Combining LCA and Key Performance Indicators for Biodiversity Assessment

The aim of this study was to combine Life Cycle Assessment (LCA) with a Key Performance Indicator (KPI) assessment focusing on biodiversity in order to examine the environmental impacts of different pig farm types (13 breeding, 23 finishing and 27 breeding-to-finishing farms) in seven European countries. In addition, the relationship between environmental impacts and selected farm management characteristics was explored. Fossil energy depletion (FED), global warming (GWP), acidification (AP) as well as marine (MEP) and fresh water (FEP) eutrophication potential were assessed by an attributional LCA and expressed per kilogram body mass net sold (BMNS). In addition, the potential biodiversity performance of all crop-livestock farms within the sample (n = 56) was evaluated with a KPI assessment of biodiversity-related field management characteristics. We found no relationship between LCA results and biodiversity scores (KPI). LCA and biodiversity performance varied more within than across farm types (breeding, finishing, breeding-to-finishing). For example, the GWP expressed per kg BMNS of the breeding unit of breeding-to-finishing farms was on average (median) 2.77 (range: 1.40–4.78) and of breeding farms 2.57 (range: 1.91–3.23) kg CO2-eq. The average (median) biodiversity theme score for breeding farms was 51% (range: 36–70%), for breeding-to-finishing farms 38% (range: 30–68%) and for finishing farms 43% (range: 28–67%). Several farm management characteristics (e.g., FCR, productivity, proportion of solid manure) correlated with all/some LCA results. Biodiversity performance depended especially on KPIs related to ecological focus areas, fertiliser management and GMO crops. The large range regarding environmental performance in both LCA and KPI assessment across farm types indicates that farm-specific improvement measures should be implemented to enhance overall environmental sustainability on farm. In conclusion, combining LCA with KPI assessment provides a more comprehensive environmental impact assessment of pig farms.

Environmental burdens of small-scale intensive pig production in China

Small-scale intensive pig production systems account for over a half of the total number of pig farms in China, of which concerns have been raised relating to their environmental performances. This study explores the cradle-to-slaughterhouse gate environmental impacts using life cycle assessment (LCA) approach, with the purpose of identifying major hotspots to formulate mitigation strategies. The functional unit is defined as 1000 kg of pig carcass weight. Consistent with previous research, feed production makes up the largest contribution (56-95%) to all the six selected impact categories based on the ReCiPe 2016 framework. Of the feed ingredients, maize is identified as the principal hotspot mainly due to the large consumption as well as the heat usage in grain steaming to enhance availability of starch digestion. The results also indicate that changes of feed consumption and composition along the lifetime growth reveal a much higher contribution from the grower-finisher stage. Marked differences are observed in terms of greenhouse gas emissions from pig production between developing (including China) and developed countries. With lots of studies showing feasibilities, improvements suggested for small-scale intensive pig production systems include the optimization of feed formulas, the introduction of new feed technologies, and the upgrade of manure management system. Our results provide valuable and practical insight for the Chinese pig supply chain to mitigate environmental burdens and achieve future environmental sustainability.

The Reduction of Crude Protein with the Supplementation of Amino Acids in the Diet Reduces the Environmental Impact of Growing Pigs Production Evaluated through Life Cycle Assessment

Two experiments were performed to determine the digestibility of diets with crude protein (CP) reduction supplemented with amino acids (18.15; 17.15; 16.15 and 15.15%) to growing pigs (30–50 kg), to assess the use of nutrients and account for the manure excretion, and to evaluate the performance, backfat thickness, Longissimus lumborum depth, and plasma urea, aiming to evaluate the environmental impact through life cycle assessment (LCA); for the first time in Brazil interacting experiments were developed to evaluate the CP reduction and LCA. The CP reduction resulted in greater daily weight gain (p = 0.011), final weight (p = 0.020), better use of N and P, through the greater N and P retained (p = 0.003 and p = 0.017, respectively). There was a linear reduction in acidification potential (p = 0.015), eutrophication potential (p = 0.001), and land occupation (p = 0.005) when dietary CP decreased from 18.15 to 15.15%. The reduction in CP and supplementation of amino acids in diets for growing pigs (30–50 kg) improved final and daily weight gain. Through LCA, and performance and metabolism data, it was concluded that for the acidification, eutrophication and land occupation categories, impacts were reduced as the protein concentration was reduced.

Agronomic and Environmental Performance of Lemnaminor Cultivated on Agricultural Wastewater Streams—A Practical Approach

This study investigated the potential of Lemna minor to valorise agricultural wastewater in protein-rich feed material in order to meet the growing demand for animal feed protein and reduce the excess of nutrients in certain European regions. For this purpose, three pilot-scale systems were monitored for 175 days under outdoor conditions in Flanders. The systems were fed with the effluent of aquaculture (pikeperch production—PP), a mixture of diluted pig manure wastewater (PM), and a synthetic medium (SM). PM showed the highest productivity (6.1 ± 2.5 g DW m−2 d−1) and N uptake (327 ± 107 mg N m−2 d−1). PP yielded a similar productivity and both wastewaters resulted in higher productivities than SM. Furthermore, all media showed similar P uptake rates (65–70 P m−2 d−1). Finally, duckweed had a beneficial amino acid composition for humans (essential amino acid index = 1.1), broilers and pigs. This study also showed that the growing medium had more influence on the productivity of duckweed than on its amino acid composition or protein content, with the latter being only slightly affected by the different media studied. Overall, these results demonstrate that duckweed can effectively remove nutrients from agriculture wastewaters while producing quality protein.

The effect of insect or microalga alternative protein feeds on broiler meat quality

BACKGROUND

In order to combat environmental and food security concerns associated with the increasing demand for soymeal related to increasing meat consumption, this study determines the chicken meat quality derived when soymeal is substituted for either partially de-fatted Hermetia illucens larval meal or spirulina (Arthrospira platensis) in broiler diets. Physicochemical parameters, sensory traits, and fatty acid composition of the meat are investigated, as well as an experiment to evaluate the impact of highly oxygenated atmosphere versus vacuum-bag packaging on shelf life was conducted.

RESULTS

Hermetia illucens did not compromise quality; meat was slightly more yellow (higher b*), had a slightly decreased pH, and was less adhesive during chewing compared to the soy-fed control. Furthermore, Hermetia illucens resulted in higher saturated fatty acids proportions in thigh meat. Spirulina resulted in redder (higher a*) and more yellow (higher b*) meat with a slightly increased umami and chicken flavour. Spirulina-fed chicken meat had higher lipid oxidation levels compared to the control after being packaged in a highly oxygenated atmosphere; although, differences between the spirulina-fed and control fatty acid composition in thigh meat were minor.

CONCLUSION

Both alternative protein feeds show potential to replace soymeal in broiler diets; however, they do result in moderately altered products.

Do dietary soy alternatives lead to pork quality improvements or drawbacks? A look into micro-alga and insect protein in swine diets

Pork quality characteristics related to the dietary substitution of soybean meal by the micro-alga Spirulina (Arthrospira platensis) or black soldier fly (Hermetia illucens) partly-defatted larval meal were observed. Through a duplicated study totalling 48 individually-fed barrows (Pietrain × (Large White × Landrace)) allocated into two experimental groups and a control, the effect of dietary protein source on physico-chemical and sensory pork quality was monitored under current industrial packaging conditions (highly‑oxygenated modified atmosphere packaging). The results show that physico-chemical characteristics are not degraded by including alternative protein sources in pig diets. Hermetia illucens increased lauric acid levels in backfat indicating that this fatty acid may be suitable as a biomarker for Hermetia illucens-fed pork. This goes to show that protein alternatives do not compromise pork quality.

Exploring the genetics of feed efficiency and feeding behaviour traits in a pig line highly selected for performance characteristics

The consideration of feed efficiency traits is highly relevant in animal breeding due to economic and ecologic impacts of the efficient usage and utilization of feed resources. In pigs, corresponding observations are recorded using automatic feeding stations and serve as one of the main criteria in most pig selection programmes. Simultaneously, feeding stations also generate feeding behaviour data which represent a nearly unused resource and provide a valuable proxy measure of health status, animal welfare, and management practices. In the current study, an integrated approach was applied to a feed efficiency tested and genome-wide genotyped terminal sire line population. Therefore, genetic analyses were performed combining a single-marker based approach and a Bayesian multi-marker algorithm. Major quantitative trait loci (QTL) for feeding behaviour traits comprising daily occupation time, daily feeder visit, and daily feeding rate were identified on chromosomes 1, 4, 6, 7, 8, and 14. Feed efficiency was represented by feed conversion ratio and daily feed intake revealing prominent genomic regions on chromosomes 1, 6, 9, and 11. The positional and functional candidate genes identified are involved in transport processes like AQP4, SLC22A23, and SLC6A14 as well as energy sensing, generation, and utilization as exemplified by PPP3CA, IQGAP3, ECI2, and DnaJC15. These molecular features provide the first step towards the dissection of the genetic connection between distinct feeding behaviour patterns, feed efficiency and performance, health, and welfare traits driving the implementation of these traits in breeding programmes and pig husbandry.