Environmental impacts of precision feeding programs applied in pig production

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.

Review: Fundamentals, limitations and pitfalls on the development and application of precision nutrition techniques for precision livestock farming

Precision livestock farming (PLF) concerns the management of livestock using the principles and technologies of process engineering. Precision nutrition (PN) is part of the PLF approach and involves the use of feeding techniques that allow the proper amount of feed with the suitable composition to be supplied in a timely manner to individual animals or groups of animals. Automatic data collection, data processing, and control actions are required activities for PN applications. Despite the benefits that PN offers to producers, few systems have been successfully implemented so far. Besides the economical and logistical challenges, there are conceptual limitations and pitfalls that threaten the widespread adoption of PN. Developers have to avoid the temptation of looking for the application of available sensors and instead concentrate on identifying the most appropriate and relevant information needed for the optimal functioning of PN applications. Efficient PN applications are obtained by controlling the nutrient requirement variations occurring between animals and over time. The utilization of feedback control algorithms for the automatic determination of optimal nutrient supply is not recommended. Mathematical models are the preferred data processing method for PN, but these models have to be designed to operate in real time using up-to-date information. These models are therefore structurally different than traditional nutrition or growth models. Combining knowledge- and data-driven models using machine learning and deep learning algorithms will enhance our ability to use real-time farm data, thus opening up new opportunities for PN. To facilitate the implementation of PN in farms, different experts and stakeholders should be involved in the development of the fully integrated and automatic PLF system. Precision livestock farming and PN should not be seen as just being a question of technology, but a successful marriage between knowledge and technology.

Mitigating environmental impacts using net energy system in feed formulation in China's pig production

As the world's largest pork producer, China is facing substantial environmental pressures caused by pig production and the relevant feed production. The net energy (NE) system is promoted as a new evaluation method to evaluate energy content in feed and energy requirements of pigs, but its application lacks of comprehensive and comparative evaluation from the environmental perspective. To identify influence factors and to develop mitigation strategies, the carbon and nitrogen footprints and land use (LU) of pigs (25-120 kg) in China were explored through scenario analysis and cradle-to-farm gate life cycle assessment (LCA). Functional unit (FU) was defined as 1 kg of live weight increase in pig. Among all the procedures of pig production, feed crop production and manure management were the principal contributors to the greenhouse gas (GHG) and nitrogen emissions. As for the carbon footprint, the GHG emissions ranged from 2.37 to 2.55 kg CO₂-eq. FU^-1 for scenarios using the NE system, 2 % lower than that of the metabolizable energy (ME) system. Cottonseed meal-based scenario generated the lowest GHG emissions, and anaerobic digestion achieved the same effects as other manure management methods. As for the nitrogen footprint, reactive nitrogen (Nr) emissions ranged from 53.4 to 66.2 g Nr FU^-1 for scenarios using the NE system, 4 % lower than that of the ME system. Peanut-based scenario won the lowest Nr losses. Moreover, arable LU ranged from 4.63 to 5.85 m² FU^-1 for scenarios using the NE system, 4 % lower than that of the ME system, and economic advantage by using the NE system was also proved. Sensitivity analysis and data quality assessment were conducted to quantify the uncertainties of the above models. In conclusion, the application of the NE system in feed formulation was an effective strategy to improve the environmental sustainability of China's pig production.

Environmental impacts of eco-nutrition swine feeding programs in spatially explicit geographic regions of the United States

This study was conducted to determine greenhouse gas (GHG) emissions, water consumption, land use, as well as nitrogen (N), phosphorus (P), and carbon (C) balance of five diet formulation strategies and feeding programs for growing-finishing pigs (25-130 kg body weight) in the three spatially explicit geographic regions where the majority of U.S. pork production occurs. Feeding programs evaluated consisted of 1) standard corn-soybean meal (CSBM) diets, 2) CSBM containing 15% corn distillers dried grains with solubles (DDGS), 3) CSBM with 8.6% thermally processed supermarket food waste (FW), 4) low crude protein CSBM diets supplemented with synthetic amino acids (SAA), and 5) CSBM with phytase enzyme (PHY) added at 600 FTU (phytase units)/kg of diet. An attributional Life Cycle Assessment approach using a highly specialized, spatially explicit Food System Supply-Chain Sustainability (FoodS3) model was used to quantify GHG emissions, water consumption, and land use of corn, soybean meal, and DDGS based on county level sourcing. The DDGS, FW, and SAA feeding programs had less estimated N and P intake and excretion than CSBM, and the PHY feeding program provided the greatest reduction in P excretion. The FW feeding program had the least overall GHG emissions (319.9 vs. 324.6 to 354.1 kg CO2 equiv./market hog), land use (331.5 vs. 346.5 to 385.2 m2/market hog), and water consumption (7.64 vs. 7.70 to 8.30 m3/market hog) among the alternatives. The DDGS feeding program had the greatest GHG emissions (354.1 kg CO2 equiv./market hog) among all programs but had less impacts on water consumption (7.70 m3) and land use (346.5 m2) per market hog than CSBM and PHY. The SAA feeding program provided a 6.5-7.4% reduction in land use impacts compared with CSBM and PHY, respectively. Regardless of feeding program, the Midwest had the least contributions to GHG emissions and land use attributed to feed and manure among regions. Water consumption per market hog associated with feeding programs was much greater in the Southwest (59.66-63.58 m3) than in the Midwest (4.45-4.88 m3) and Mid-Atlantic (1.85-2.14 m3) regions. Results show that diet composition and U.S. geographic region significantly affect GHG emissions, water consumption, and land use of pork production systems, and the potential use of thermally processed supermarket food waste at relatively low diet inclusion rates (<10%) can reduce environmental impacts compared with other common feeding strategies.

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.

β-Mannanase Supplementation as an Eco-Friendly Feed Strategy to Reduce the Environmental Impacts of Pig and Poultry Feeding Programs

Little is still known about the environmental impacts of exogenous enzyme supplementation in pig and poultry feeding programs. Thus, this study aimed to assess the potential environmental impacts of producing feeds for pigs and broilers by simulating the effects of β-mannanase Hemicell™ HT supplementation through energy savings during diet formulation. Life-cycle assessment standards were applied to simulate a cradle-to-feed mill gate scope. The functional units used were the production of 1 kg of the enzyme and 1 kg of feed at a feed mill gate located in Concórdia, Santa Catarina, Brazil. Climate change, eutrophication, and acidification were the chosen environmental impact categories. Energy savings through β-mannanase supplementation were assessed by different metabolizable energy (ME) matrices (45 or 90 kcal of ME/kg of feed) during diet formulation in different grain production scenarios (Southern and/or Central-West origin). A total of 28 feeds were formulated based on the nutritional requirements and feeding programs described in the Brazilian Tables for Poultry and Swine. The least-cost formulation method was used based on real price averages practiced in a local industry over 12 months. The production of 1 kg of β-mannanase was associated with the emission of 1,800 g of CO₂-eq, 4.53 g of PO₄-eq, and 7.89 g of SO₂-eq. For pig feeds, β-mannanase supplementation mitigated both climate change and eutrophication impacts up to 8.5 and 1.4% (45 kcal of ME/kg of feed) or up to 16.2 and 2.7% (90 kcal of ME/kg of feed) compared to control diets formulated without the enzyme. For broiler feeds, these impacts were mitigated up to 5.6 and 1.1% (45 kcal of ME/kg of feed), respectively. On the other hand, the effect of using β-mannanase on the acidification impact was not consistent among feeds/species. Overall, β-mannanase supplementation reduced the amount of soybean oil in feed formulas, which is associated with high environmental impacts. Consequently, the potential impacts of climate change and eutrophication associated with producing feeds for pigs and broilers were substantially mitigated. These results suggest that β-mannanase supplementation is an eco-friendly feed strategy to reduce the environmental impacts of pig and poultry feeding programs.

Environmental Impacts and Their Association With Performance and Excretion Traits in Growing Pigs

The selection of pigs for improved production traits has been, for a long time, the major driver of pig breeding. More recently, because of the increasing concern with the environment, new selection criteria have been explored, such as nitrogen (N) excretion. However, many studies indicate that life cycle assessment (LCA) provides much better indicators of environmental impacts than excretion. Therefore, the objective of this study was to investigate, using a modeling approach, the relationships between production traits and LCA impacts of individual growing pigs calculated at the farm gate for 1 kg of body weight gain. Performances of pigs were simulated for 2-phase (2P) and precision feeding (PR), using the InraPorc population model (on 1,000 pigs). Nitrogen excretion was positively correlated with feed conversion ratio (FCR; r = +0.96), climate change (CC; r = +0.96), acidification potential (AC; r = +0.97), eutrophication potential (EU; r = +0.97), and land occupation (LO; r = +0.96), whatever the feeding program. However, FCR appeared to be a better indicator of LCA impacts, with very high and positive correlations (r > +0.99) with CC, AC, EU, and LO for both feeding programs. The CC, AC, and EU impacts of pig production for PR feeding were 1.3, 10, and 7.5% lower than for 2P, respectively, but the correlations within each outcome were very similar among feeding programs. It was concluded that the use of FCR as a selection criterion in pig breeding seems to be a promising approach to associate improved performance and low environmental impact of pig fattening.

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.

Reducing environmental impacts of feed using multiobjective formulation: What benefits at the farm gate for pig and broiler production?

Feed production is the main contributor to several environmental impacts of livestock. To decrease environmental impacts of feed, those of feedstuffs should be considered during formulation. In particular, multiobjective feed formulation (MOF) can help reduce several environmental impacts simultaneously while keeping any increase in feed price moderate. The objective of this study was to assess environmental benefits of MOF at the farm gate for fattening pigs and broilers. For pigs, three feeding strategies were tested: classic 2-phase (2P), 2-phase with lower net energy content (2P-), and multiphase (MP). For broilers, two strategies were tested: classic 3-phase (3P) and 3-phase with higher digestible amino acid contents and lower metabolisable energy content (3P+). Diets were formulated using both least-cost formulation (LCF) and MOF, yielding six pig scenarios and four broiler scenarios. Environmental impacts at the farm gate were estimated using a modelling approach based on life cycle assessment. Indicators for six impact categories were then calculated: climate change (CC), cumulative non-renewable energy demand (CEDNR), acidification (AC), eutrophication (EU), land occupation (LO), and phosphorus demand (PD). As expected, MOF had lower farm-gate impacts than LCF (as much as -13%), but the degree of decrease varied by feeding strategy and impact. For pigs, MOF was equally effective in all strategies at reducing PD (-6 to -9%) and AC (-2%). In contrast, MOF was more effective in 2P and 2P- at decreasing CC (-5% to -7%), LO (-9% to -13%) and EU (-6% to -8%) than in MP (CC: -2%; LO: -4%; EU: -3%). The benefit of MOF was found greater in 2P (-7%) than in other pig strategies for CEDNR (-3 to +0%). For broilers, MOF was equally effective in both strategies tested at decreasing PD (-12%), AC (-2%), and EU (-4%). For CC and CEDNR, MOF was more effective in 3P (CC: -9%; CEDNR: -11%) than 3P+ (-6% for both impacts), but not for LO (+3% in 3P vs -1% in 3P+). These differences were due mainly to differences in animal performance (especially feed conversion ratio) among the strategies tested. Finally, in all scenarios, gross margin at the farm gate decreased with MOF comparatively to LCF (pigs: -3% to -11%); broilers: -7% to -11%). These results demonstrate the importance of comprehensive economic and environmental optimisation of feeding strategies by simultaneously considering feed impacts, animal performance, and manure management. To do so, further research is therefore required to develop new modelling tools.

Modeling nutritional and performance factors that influence the efficiency of weight gain in relation to excreted nitrogen in weaning piglets

One of the most debated topics in pig production is the need to study, understand and change the production system in order to improve nutrient efficiency, becoming more environmentally friendly. The nitrogen excretion has highly deleterious effects on the environment, and it is necessary to develop tools that help to reduce the excretion of this compound without compromising productivity. Therefore, two models were generated to estimate the efficiency of weight gain in relation to excreted nitrogen in post-weaning piglets. Data for testing these models were obtained from previous master and PhD studies carried out at the Federal University of Rio Grande do Sul, Animal Science Laboratory using piglets in the post-weaning phase with results for performance and digestibility. The database that was constructed was composed of raw data from 10 studies carried out between 2000 and 2016, on a total of 726 piglets weaned at ages between 17 and 28 days, and to which 62 different treatments were applied. An exploratory analysis of the data was done by evaluating scatter plots and histograms, and variables representing different treatments were used in a stepwise multiple linear regression analysis, with the F-test used as the selection criterion. Two models were generated that either considered the nitrogen retained or not, to estimate the ratio between weight gain and excreted nitrogen using generalized linear model procedure. The authors analyzed the behavior of each variable to evaluate whether the equation generated was biologically coherent. Weight gain, dry matter intake, nitrogen intake, metabolizable energy intake, retained nitrogen and urinary nitrogen were all significant (P<0.001) variables in model I, and in model II the variable fecal nitrogen was also included. The models had high coefficients of determination (R2 of model I and II were 0.9013 and 0.8271, respectively), and the nitrogen ingested variable was the one that most strongly influenced growth efficiency. When the retained nitrogen variable was removed from the model, there was a reduction in the fit of the equations. It was possible to conclude that both of the two models generated could be applied and the amount of nitrogen ingested had the greatest influence on growth efficiency related to nitrogen excretion.