The effects of welfare-enhancing system changes on the environmental impacts of broiler and egg production.

ENVIRONMENT, WELL-BEING, AND BEHAVIOR The effects of welfare-enhancing system changes on the environmental impacts of broiler and egg production I. Leinonen,*1 A. G. Williams,† and I. Kyriazakis* *School of Agriculture, Food and Rural Development, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK; and †School of Applied Sciences, Cranfield University, Bedford, MK43 0AL, UK indoor system, due to increased heating requirements. However, when combined with the heat exchanger, the GWP was actually reduced by 3% when compared with the standard system. Both alternative systems for broilers resulted in a reduction in the eutrophication potential (by up to 8%) and acidification potential (by up to 10%). The results also showed that the colony cage system had 8% lower primary energy use and 3% lower GWP than the baseline cage system, due to better energy use efficiency and slightly improved productivity. There were only minor differences in the eutrophication and acidification potentials between different egg production systems. The results suggest that welfarefriendly changes in chicken systems can be achieved without a compromise in their environmental impacts.

Key words: broiler, egg, environmental impact, life cycle assessment, welfare 2014 Poultry Science 93:256–266 http://dx.doi.org/10.3382/ps.2013-03252

INTRODUCTION

demand for birds produced in more extensive housing systems, including lower stocking densities. Conventional, usually intensive poultry systems have been generally considered to be environmentally friendly because of their efficiency [i.e., low resource use and emissions per unit of product (e.g., Leinonen et al., 2012a,b)]. Therefore, it is understandable that there are some concerns about the environmental impacts of the more extensive systems that aim to improve animal welfare (Xin et al., 2011; Foresight, 2011). Conversely, it has been reported that at least 30% of practices that aim to reduce environmental impact in UK livestock systems are incompatible with animal welfare (Moorhouse et al., 2009). The key question then is: does a trade-off between low environmental impacts and high animal welfare exist, or can improvements in both these areas be achieved simultaneously? A quantitative, holistic method is needed to evaluate the overall effect of changes in the production systems on the environmental impact of poultry production. A method called environmental life cycle assessment (LCA) is generally preferred because it accounts for all environmental burdens occurring during the production cycle, starting from raw material extraction through to

Although poultry production has been found to be relatively environmentally friendly compared with several other livestock production systems (e.g., de Vries and de Boer, 2010), it still has the potential to reduce its environmental impacts even further, for example by applying novel environmental technologies. The question is whether efforts toward this can be achieved without detriment to animal welfare, and vice versa (Moorhouse et al., 2009). Consumers of agricultural commodities are increasingly sensitive to animal welfare, and new systems aiming at improving this have recently been introduced to EU livestock production. For example, the conventional battery cage system used for chicken egg production was banned in the European Union in 2012 (i.e., European Union Council Directive 1999/74/ EC), and fully housed production was mainly replaced by new enriched colony cages (or free range production). In broiler production, there is also an increasing ©2014 Poultry Science Association Inc. Received April 19, 2013. Accepted November 3, 2013. 1 Corresponding author: [email protected]

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ABSTRACT The environmental impacts of 2 alternative UK broiler production systems that aim to improve bird welfare (a lower stocking density indoor system and the same system combined with heat exchangers for ventilation air) were compared with the baseline standard indoor system of broiler production. Furthermore, the environmental impacts of egg production in the conventional battery cage system (banned in the European Union in 2012) and its replacement, the enriched colony cage system, were compared. All comparisons were based on data obtained from the UK poultry industry, and the life cycle assessment method from cradle to farm gate was applied in the analyses. The results show that the lower density system slightly increased the global warming potential (GWP) of broiler production (by 2%), compared with the standard

ENVIRONMENTAL IMPACTS AND WELFARE OF CHICKEN

MATERIALS AND METHODS Systems Approach The general approach taken in the current study was based on systems modeling of production as described by Williams et al. (2006, 2007, 2010). This included structural models of the industry and process-based simulation models that were unified in the systems approach so that changes in one area caused consistent interactions elsewhere. This approach was applied to both feed crop and animal production. The systems modeled in this study included the whole feed production chain (crop production, noncrop nutrient production, feed processing, and transport), breeding of broilers and layers, the production stage of broilers and eggs (including farm energy and water use and gaseous emissions from housing), and manure and general waste management, as described by Williams et al. (2006) and applied for poultry systems by Leinonen et al. (2012a,b). In earlier studies (Leinonen et al., 2012a,b), the environmental impacts of the main broiler and egg production systems in the United Kingdom were quantified. The data from these studies were applied here to quantify the main inputs and outputs of the baseline systems (standard indoor broiler production and conventional battery cage egg production). To evaluate the effects of system changes on the environmental impacts, the following comparisons were made with the baselines and the scenarios with alternative systems: 1) Standard indoor broiler system (37 kg of live weight/m2) vs. low density (30 kg/m2) indoor broiler system.

2) Standard indoor broiler system versus low density indoor broiler system with a heat exchanger applied for ventilation air, aiming to reduce any increased heating requirement of the low density system. It is accepted that heat exchangers are needed for these systems to work effectively, so this is a necessary step change. 3) Conventional cage egg production systems versus colony cage system. The new colony cages provide the floor area of 0.075 m2 per bird, including a nest box, perching space, and scratching area. In the conventional cage system, the minimum allowed floor area was 0.055 m2 per bird.

Production Model The structural model for broiler and egg systems calculated all of the inputs required to produce the functional unit (FU) of either 1,000 kg of expected carcass weight in broilers (including also wings and bones but excluding feathers, heads, necks, feet, and internal organs) or 1,000 kg of marketable eggs (Gerber et al., 2013), allowing for breeding overheads, mortalities, and productivity levels. It also calculated the outputs, both useful (broilers, eggs, and spent hens) and unwanted (e.g., wastes and mortalities). Economic allocation was used in distribution the burdens between useful outputs. As a result, a small proportion of the impacts of egg production was allocated to the meat produced from spent hens, whereas in broiler production, the broiler carcass was considered to be the only useful output. In the model, changes in the proportion of any activity (e.g., breeding, broiler finishing, pullet rearing, egg laying) must result in changes to the proportions of others to keep producing the desired amount of output. Establishing how much of each activity was required (e.g., the number of breeder birds per produced FU) was found by solving linear equations that described the relationships that linked the activities together. For further details of the structural model, see the Appendix. Mechanistic animal growth, production, and feed intake models were used in the current study to calculate the total consumption of each feed ingredient during the whole production cycle, and to calculate the amounts of main plant nutrients, N, P, and K , in manure excreted by the birds during the production cycle. The model, described by Leinonen et al. (2012a,b), was based on the principles presented by Emmans and Kyriazakis (2001) and Wellock et al. (2003) and predicted the daily feed intake of a single bird as a function of feed composition and energy and protein requirements of the bird. This included requirements for both production (body growth and eggs) and maintenance. The model was calibrated to match the real production, feed intake, and mortality data provided by the broiler and egg industry for different systems (Leinonen et al., 2012a,b), by adjusting the model parameters for growth rate, energy requirement for maintenance and


the end products (BSI, 2006). Unlike other methods for environmental impact assessment (e.g., BSI, 2011), LCA is not limited to carbon footprinting only. Instead, it uses several indicators of environmental impacts, including resource use and potential for causing harm to ecosystems and humans, for example, global warming from greenhouse gas emissions, eutrophication from nitrate and phosphate leaching, and acidification as a result of ammonia emissions and fossil fuel use. The aim of this study was to apply the attributional LCA method “from cradle to farm gate,” to quantify the effect of new, animal welfare-enhancing production systems that have recently been introduced in broiler and egg production systems in the European Union, on their environmental impacts. This analysis was based on data collected from the UK broiler and egg production industry, which were used as inputs for mechanistic and structural models which quantified the environmental impacts of these systems. The analysis covered both the traditional main production systems (standard indoor broilers and cage eggs) and new systems including colony cage egg production and low stocking density broilers.

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Crop and Manure Submodels A separate submodel for arable production was used to quantify the environmental impacts of the main feed ingredients, with main features as in Williams et al. (2010). All major crops used for production of poultry feed were modeled. For the crops produced overseas (soy, sunflower, palm oil), the production was modeled as closely as possible using local techniques. Transport burdens for importing overseas crops and burdens from processing the feed were also included. For the nutrient dynamics, the current study followed the principles of Audsley et al. (1997) and Williams et al. (2006, 2010), taking a long-term approach to agriculture, for example ensuring that N emissions and uptake from manure are accounted for on an infinite time horizon. This differs from the shorter term methods that are often applied in more empirically based carbon footprinting (e.g., BSI, 2011). Poultry manure is the source of direct gaseous emissions of ammonia (NH3), nitrous oxide (N2O), and to a lesser extent methane (CH4), which occur during housing, storage, and land-spreading. In this study, these were quantified with a separate manure submodel. Manure management also uses energy, and these burdens were debited against the poultry (along with burdens from direct gaseous emissions). In the model, all of the nutrients that were applied to the soil as manure were accounted for as either crop products or as losses to the environment (Sandars et al., 2003). The benefits of plant nutrients (N, P, and K) remaining in soil after land application were credited to poultry using system expansion. This was done by offsetting the need to apply fertilizer to winter wheat as described by Sandars et al. (2003) and implemented by Williams et al. (2006). See Appendix for further details of the crop production and manure models.

Activity Data Although the outputs of this study (i.e., the environmental impacts of the poultry systems) were quanti-

fied using model calculations, the possible differences between the systems were based entirely on the actual activity data provided by the industry. The study compared existing production systems and therefore the principles of attributional LCA were applied in this work. The industrial data were used in the modeling either directly as an input or for calibration of the mechanistic submodels. Separate data sets were obtained from both broiler and egg production industries. Broiler Production Data. Data on the standard indoor broiler production system and the alternative systems were provided by major broiler producers, which were stakeholders in this study and were considered to be representative of the overall UK broiler industry. These figures included data such as average finishing age and finishing weight, stocking density, average feed intake, and mortality. The broiler genotype used in all systems considered was Ross 308, and a typical size of the broiler house was about 1,500 m2. General information on the industry structure, including broiler rearing, finishing, breeding, and feed processing, was also obtained from the industry. For detailed data on different activities considered in the current study, typical production units were selected to represent both the standard indoor and the alternative broiler production systems, while the same breeding system was assumed to be applied for all scenarios. For breeding, 3 generations of breeding flocks, their required inputs, and the environmental impacts arising from them were included in the analysis (Gerber et al., 2013). The male/female ratio of the breeding flocks was obtained from the industry, and the unwanted chicks in breeder systems were understood to be killed after hatching. Breeder meat was not considered as a useful output in this study, and therefore all burdens of the breeding systems were allocated to broiler production. Breeder carcasses only contribute about 0.6% to total carcass output, which is below 0.1% on an economic value basis. The energy consumption for heating, lighting, ventilation, and feeding for the standard and alternative systems was obtained directly from these typical farms. Information about the type and amount of bedding was also obtained from the industry. In this study, it was assumed that all broiler litter was transported for soil improvement in all systems, which is a general practice in the UK broiler systems. Egg Production Data. Both the conventional cage and the colony cage egg production systems in this study consisted of egg laying, pullet rearing, and breeding. For this study, it was assumed that identical breeding and rearing systems were applied for both the conventional and colony cage laying systems, whereas for the data for the laying period, separate data sets were applied for each system considered in this study. As with broiler production, 3 generations of breeding flocks were included in the model, and the data on male/female ratio, breeder feed, and so on was obtained from industry. The rearing period lasted 16 wk and the


egg production. In the case where thinning was applied in broiler production, the model was run separately for thinned and remaining birds, and weighted average of the outputs was applied in further analyses. The model calculates the N, P, and K contents of the manure according to the mass balance principle (i.e., the nutrients retained both in the animal body and eggs were subtracted from the total amount of nutrients obtained from the feed). In addition to the nutrients excreted by the birds, nutrients in the spilled feed were added to the manure in the calculations. For the purpose of the study, it was assumed that all broiler litter and pullet, layer, and breeder manure was used for soil improvement as a fertilizer, and was used as an input of separate crop and manure submodels as described below.


Sneddon et al., 2008). Additional data, such as life cycle inventories (LCI) of agricultural buildings and machinery, came from Williams et al. (2006).

Environmental Impacts Emissions to the environment were aggregated into environmentally functional groups as follows: Primary Energy Use. The energy use includes diesel (e.g., feed production and transport), electricity (e.g., ventilation and lighting), and gas (e.g., heating). These are all quantified in terms of the primary energy needed for extraction and supply of fuels (otherwise known as energy carriers). The primary fuels are coal, natural gas, oil, and uranium (nuclear electricity). They are quantified as MJ primary energy, which varies from about 1.1 MJ of natural gas per MJ available process energy to 3.6 MJ of primary energy per MJ of electricity. Data on the origin and proportion of energy carriers in electricity in the United Kingdom and overseas came mainly from the European Reference Life Cycle Database (JRC, 2013), or were derived from the International Energy Agency. A proportion of electricity is produced by renewable sources such as wind and hydropower, which account for 3.6 and 8% for UK and European electricity, respectively. Global Warming Potential. The main sources of global warming potential (GWP) in poultry industry are carbon dioxide (CO2) from fossil fuel, nitrous oxide (N2O), and methane (CH4). Global warming potential was quantified in terms of CO2 equivalent: with a 100yr timescale 1 kg of CH4 and N2O are equivalent to 25 and 298 kg of CO2, respectively (IPCC, 2006). Eutrophication Potential. Eutrophication potential (EP) was calculated using the method of the Institute of Environmental Sciences at Leiden University (http://www.leidenuniv.nl/interfac/cml/ssp/index. html). The main sources are nitrate (NO3−) and phosphate (PO43−) leaching to water and ammonia (NH3) emissions to air. The EP was quantified in terms of phosphate equivalents: 1 kg of NO3-N and NH3-N are equivalent to 0.44 and 0.43 kg of PO43−, respectively. Acidification Potential. Acidification potential (AP) was also calculated using the method of the Institute of Environmental Sciences. The main source in poultry industry is ammonia emissions, together with sulfur dioxide (SO2) from fossil fuel combustion. Ammonia contributes to AP despite being alkaline; when emitted to the atmosphere it is oxidized to nitric acid. The AP was quantified in terms of SO2 equivalents: 1 kg of NH3-N is equivalent to 2.3 kg of SO2.

Breakdown of Environmental Impacts The results were broken down by the following material (and energy) flow categories to demonstrate the reasons for the differences in impacts between the systems.


laying period in both the conventional and colony cage systems was 56 wk, as is the common practice. The bird genotype in the both systems was Hy-Line Brown, which is widely used by the UK egg production industry. According to the breed manual, the birds have a body mass of 1.4 kg at the age of 17 wk and 1.98 kg at age of 70 wk (Hy-Line, 2009). For feed intake, egg production, and mortality, figures provided by the UK egg industry for both of the systems were used. The actual energy consumption for heating, lighting, ventilation, and feeding was based on average data from farms representing each of the systems considered, as provided by the industry. The end use of manure was identical for all systems (i.e., it was assumed that all pullet, layer, and breeder manure was transported for soil improvement). Other Input Data. As the inputs used in the model were based on long-term data, it can be expected that the diets used for this period did not remain constant in either the broiler or egg production systems. However, it was not possible to obtain any detailed information on such diet changes, and for this reason the environmental impacts were calculated in the model using generalized broiler and layer diets representative of those used in the UK poultry industry (Leinonen et al., 2012a,b). These diets were assumed to be valid for both the conventional and alternative systems. In the scenarios considered, broiler diets changed 4 times during the growing period and layer diets changed 5 times during the whole cycle according to common practice. Both broiler and layer diets had wheat as the main energy source and soybean meal as the main protein source. Small amounts of synthetic amino acids were included in the diets to keep the amino acid balance at the optimum level. See Supplemental Tables 1 and 2 (http://dx.doi.org/10.3382/ps.2013-03252) for the details of the broiler and layer diets applied in this study. When the environmental impacts of the production of feed ingredients were quantified, the CO2 emissions caused by the land use changes (mainly conversion of rainforest or grassland to agricultural use) of soy production were also included. For this, the “best estimate” method recommended by the PAS 2050 specification (BSI, 2011) was applied. According to this method, because the exact origin of the soy used in the diets was not known, it was assumed to originate partly from mature and partly from newly converted agricultural land, and the proportions of these were assumed to be the weighted averages specific for each producing country (Brazil and Argentina), as described by Leinonen et al. (2012a,b, 2013). See Appendix for details of the calculations of the greenhouse gas emissions related to land use change. Emissions of NH3, N2O, and CH4 from housing for both broiler and egg production systems were calculated following the methods of Williams et al. (2006), which are based on the UK national inventories (Chadwick et al., 1999; IPCC, 2006; Misselbrook et al., 2008;

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Leinonen et al. Table 1. Production and input figures for the standard indoor broiler system and alternative broiler production scenarios considered Item Initial stocking density, birds/m2 Final age, d Average final weight, kg Feed intake per bird, kg Feed conversion ratio, kg/kg Mortality, % LPG4 used per bird, L Electricity used per bird, kWh Breeder birds per FU5

Standard indoor

Low density

Low density + heat exchanger

20 391 1.952 3.363 1.723 3.5 0.19 0.19 5.91

16 35 1.89 3.09 1.63 3.7 0.34 0.20 6.12

16 35 1.90 3.07 1.62 4.3 0.22 0.21 6.12

1Final

age of broilers remaining after thinning. percent of birds removed in thinning at 1.8 kg weight. The final weight of remaining birds was 2.0 kg. The results are based on the weighted average of these 2 groups of birds. 3Based on the total feed intake during the production cycle. The feed intake by thinned birds was not recorded separately by the industry. 4Liquefied petroleum gas. 5Three generations of breeder birds, FU = functional unit. 2Twenty-five

RESULTS AND DISCUSSION Inputs and Outputs of Different Systems Broiler Production Systems. The main production figures for different broiler systems are shown in Table 1. It should be noted that as the production inputs were not measured separately for thinned birds and birds remaining after thinning, the results of the standard indoor system are shown for an average bird, the weight of which is the weighted average of the final weights of these 2 groups of birds. As shown in Table 1, in addition to different stocking densities, another difference between the systems was that in the low density systems the birds were slaughtered earlier to maintain the stocking density within desirable limits. Because the feed conversion ratio is di-

rectly dependent on bird age, the birds in the low density systems consumed less feed per produced carcass weight than the birds in the standard indoor system. Bird mortality was slightly higher in the low density systems than in the standard indoor system, according to the industry data. The reason for this difference is not known, but in any case, it had a very minor effect on the results. Furthermore, due to lower bird numbers per house, the requirement of construction materials, and so on, per unit of output were higher in low density systems than in the standard indoor systems, because a lower amount of the output could be produced per house at an equal time period. Again, these differences had only a minimal effect on the overall environmental impacts of different systems. There were major differences between the conventional and the alternative broiler systems in direct energy consumption during housing (Table 1). The farm liquefied petroleum gas (LPG) consumption increased more than 50% in the low density system compared with the standard indoor system. This was caused by increased heating requirements because a lower number of birds produced less heat. However, when the low density system was combined with the heat exchanger that reduced the energy loss with ventilation air, the increase of LPG consumption compared with the baseline system was relatively low (about 10%). The heat exchanger did not significantly increase the overall electricity consumption of the farm. Egg Production Systems. The production figures for the baseline cage egg production system and the colony cage system are shown in Table 2. There was a small increase in the number of eggs produced per bird from the colony system compared with the conventional cage system. This change was largely caused by reduced mortality in the colony system. There was a slight increase of feed intake per bird in the colony cage system, according to the industry data. This was probably a result of higher physical activity of the birds, although the exact reason cannot be confirmed because there


1) Feed, including production of crops and additives, feed processing, and transport. This category also includes the water consumed during housing. 2) Farm electricity, direct consumption at the farms (breeding, broiler growing, pullet rearing, and egg laying) and hatcheries, not including feed production, processing, and transport. 3) Farm gas and oil, direct consumption at the farms and hatcheries, not including feed production, processing, and transport. 4) Housing, including direct emissions of NH3, CH4, and N2O from housing and burdens from construction of farm buildings and vehicles, not including buildings and vehicles used in feed production, processing, and transport of ingredients. 5) Manure and bedding, including emissions from manure storage and field spreading and the production of the bedding. This category also includes credits from replacing synthetic fertilizers. It does not include direct emissions of NH3, CH4, and N2O from housing.

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ENVIRONMENTAL IMPACTS AND WELFARE OF CHICKEN Table 2. Production and input figures for the baseline and the colony cage egg laying scenarios1

Item Laying cycle, wk Eggs per bird Egg weight, g Feed intake per day, g Mortality, % Electricity used per bird, kWh Breeder birds per FU2

Conventional cage (baseline)

Colony cage

56 315 62 115 3.5 5.9 0.63

56 320 62 116 2.5 3.9 0.62

1The figures do not include the pullet rearing stage, which was assumed to be identical for both systems 2Three generations of breeder birds, FU = functional unit.

Table 4. Global warming potential (1,000 kg of CO2 equivalent, 100-yr timescale) for the different broiler production systems considered per 1,000 kg of expected carcass weight

Category Feed + water Farm electricity Farm gas + oil Housing Manure + bedding Total

Standard

Low density


3.08 0.16 0.43 0.54 0.14 4.35

2.95 0.18 0.68 0.49 0.13 4.42

2.94 0.18 0.48 0.49 0.13 4.22

Table 3. Primary energy use (GJ) for the different broiler production systems considered per 1,000 kg of expected carcass weight

Table 5. Eutrophication potential (kg of PO4 equivalent) for the different broiler production systems considered per 1,000 kg of expected carcass weight

were no actual measurements of bird activity available. The electricity consumption per bird was clearly lower in the colony system than in the conventional system. This may partly be a result of reduced heat production and ventilation requirement due to lower stocking density of the birds. On the other hand, this result may indicate the generally improved energy efficiency of the buildings in the new system, including more efficient ventilation, feeding, egg collection, and lighting. Unlike in broiler production, there were no significant differences in the gas and oil consumption between the alternative laying systems because no heating was applied in the laying stage and the pullet rearing stage was assumed to be identical for both systems.

Environmental Impacts of Different Systems

Category Feed Farm electricity Farm gas + oil Housing Manure + bedding Total

Standard

Low density


15.9 2.8 6.3 0.2 −0.3 24.9

15.3 3.0 9.8 0.2 −0.3 28.0

15.2 3.1 7.0 0.2 −0.3 25.2


Standard

Low density


10.69 0.00 0.04 1.04 8.73 20.51

10.26 0.00 0.07 0.96 7.90 19.18

10.21 0.00 0.05 0.94 7.71 18.90


The detailed results of the effects of system changes on environmental impacts of the whole broiler production chain are presented in Tables 3, 4, 5, and 6. The results show that the low density system increased the primary energy use (Table 3), mainly due to increased LPG consumption during housing. Increased LPG consumption also adversely affected GWP (Table 4). However, the increase of farm energy use was partly compensated by reduced feed intake per FU (by about 5%) and shorter production cycle because these factors reduced the greenhouse gas emissions related to feed production and also N2O emissions from housing and end use of manure. As a combined effect of these changes, the overall increase of GWP was only 2%, when the

low density system was compared with the baseline system. As in previous studies on environmental impacts of broiler production (e.g., Pelletier, 2008; Leinonen et al., 2012a), feed production, processing, and transport in this study had a higher contribution to the GWP (67 to 71%) than any other material flow category, including the farm energy use. So, even the modest reduction of feed consumption from the shorter production cycle in the low density systems could largely counterbalance the strong relative increase of direct LPG consumption during housing. Despite the apparent benefit of shorter production cycle on the environmental impacts of broiler production in this study, it should be noted that this result may not be generally applicable across livestock production systems. In relation to the variation in the length of the production cycle, there is a trade-off between the impacts related to the feed consumption of the production animals and the impacts occurring at earlier stages of the production chain, including breeding and hatching in poultry systems. In broiler production, shorter production cycles also mean lower yield per bird and therefore also increase the number of breeder birds (and hatched chicks) needed to produce the FU. Leinonen et al. (2012a) found that the GWP related to broiler breeding is about 8% of the total GWP of standard indoor broiler production, so, in principle, changes in the breeding system may have a significant contribution to the overall environmental impacts of the whole production chain. However, in the present study, the required number of breeder birds increased only by about 3% in the low density systems compared with the standard system. So, this had a relatively small effect in com-

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Table 6. Acidification potential (kg of SO2 equivalent) for the different broiler production systems considered per 1,000 kg of expected carcass weight


Standard

Low density


11.64 0.55 0.57 5.62 28.64 47.02

11.16 0.60 0.87 5.16 25.47 43.25

11.11 0.61 0.63 5.05 24.76 42.16

Table 7. Primary energy use (GJ) for the different egg production systems considered per 1,000 kg of eggs Category Feed + water Farm electricity Farm gas + oil Housing Manure + bedding Total

Conventional cage

Colony cage

11.6 4.1 1.3 0.2 −0.4 16.8

11.5 2.9 1.1 0.2 −0.4 15.4


Conventional cage

Colony cage

2.10 0.24 0.09 0.38 0.11 2.92

2.10 0.17 0.08 0.38 0.11 2.83

into the system will cause a similar change in the absolute amount of the excreted nutrients, and this may easily have significant effects on both eutrophication and acidification. The environmental impacts of different egg production scenarios are presented in Tables 7, 8, 9, and 10. The results showed that the colony cage system had 8% lower primary energy use and 3% lower GWP than the baseline battery cage system, due to lower energy use per unit product and slightly improved productivity. There were only minor differences in the eutrophication and acidification potentials between the systems, as there were no significant changes in feed consumption or nutrient excretion per FU, when the conventional cage system was replaced by the colony cages. Although improved productivity slightly reduced the amount of breeder birds required per FU, this had only a minimal effect on the environmental impacts, as the breeding system in egg production has much smaller contribution than in broiler production. To compare systematically the environmental impacts of different systems, the uncertainty related to the estimates of the impact categories should also be taken into account. In earlier LCA studies related to poultry production (Leinonen et al., 2012a,b), the uncertainty was estimated using Monte-Carlo simulations, as suggested by Wiltshire et al. (2009). With this method, the variation related to the input variables and model parameters was included in the model runs, and as a result, the models provided an estimate for the CV of the outputs. In the present study, it was not possible to get reliable estimates of the variation of the input data related to the new poultry systems, due to their recent introduction to the industry. However, earlier estimates suggest that for example in the case of the estimated Table 9. Eutrophication potential (kg of PO4 equivalent) for the different egg production systems considered per 1,000 kg of eggs Category Feed + water Farm electricity Farm gas + oil Housing Manure + bedding Total

Conventional cage

Colony cage

7.80 0.00 0.01 3.61 7.60 19.02

7.78 0.00 0.01 3.60 7.57 18.96


parison with the benefits of reduced feed consumption of the broiler birds. As a result of only moderately increased LPG and reduced feed conversion ratio, the overall primary energy use in the low density system applying the heat exchanger was similar as in the baseline system, and the GWP was actually reduced by 3%. This result demonstrates the potential of new environmental technologies to improve the energy efficiency of livestock production systems, and therefore also to reduce their environmental impacts. Because reduction in energy consumption could also reduce recurring running costs, it can be expected that the development of future housing systems will also bring some environmental benefits to livestock production. It should also be noted that although in the present study the heat exchanger data were only available in combination with the low density broiler system, where it has most economic benefit due to higher heating requirement, it can be expected that applying the heat exchange could have environmental benefits also in the conventional indoor broiler system, if applied there. As shown in Tables 5 and 6, both alternative systems resulted in reduction in the EP (by up to 8%) and AP (by up to 10%). This was mainly caused by lower feed conversion ratio compared with the baseline system. As previously observed in poultry production systems (e.g., Leinonen et al., 2012a,b, 2013), the changes in the nutrient emissions from housing and manure are in relative terms higher than the changes in nutrient intake per FU. The reason for this is that independent of the nutrient intake, the nutrient content in the animal body can be considered to remain relatively unchanged. Therefore, according to the mass balance principle, any increase or decrease in the amount of nutrients entering

Table 8. Global warming potential (1,000 kg of CO2 equivalent, 100-yr timescale) for the different egg production systems considered per 1,000 kg of eggs

ENVIRONMENTAL IMPACTS AND WELFARE OF CHICKEN Table 10. Acidification potential (kg of SO2 equivalent) for the different egg production systems considered per 1,000 kg of eggs Category Feed + water Farm electricity Farm gas + oil Housing Manure + bedding Total

Conventional cage

Colony cage

8.24 0.96 0.16 19.42 26.72 55.50

8.21 0.68 0.14 19.36 26.63 55.02

Intensity, Environmental Impacts, and Welfare in Livestock Systems In several earlier studies on livestock production, intensive systems have been found to have lower environmental impacts per unit product than more extensive systems. This was observed in broiler and egg production (Mollenhorst et al., 2006; Leinonen et al., 2012a,b), in pork production (Basset-Mens and Van der Werf, 2005), and in beef and dairy cattle systems (Crosson et al., 2011). However, opposite results have also been observed, showing that organic or other extensive forms of production can reduce the use of fossil fuels, fertilizers, and other inputs (e.g., Haas et al., 2001; BassetMens et al., 2009; Boggia et al., 2010) or have lower emissions from housing (e.g., Dekker et al., 2011), and therefore can have equal or less environmental impact than intensive systems. In earlier studies of UK poultry production (Leinonen et al., 2012a,b), it was found that extensive systems (free range and organic) had generally higher GWP, EP, and AP than conventional systems (standard indoor broiler production and cage egg laying), although these differences were not always statistically significant. In those studies, the differences between the systems were largely related to productivity, and especially to the amount of feed consumed per unit product. This was generally higher in extensive than in the conventional systems. Feed intake has also an important role in the results of the present study, which shows that when the feed conversion ratio in the alternative systems remains equal or lower than in the conventional systems, there is no dramatic increase in the environmental impacts either. Sustainable intensification is considered by many the way forward for the production of global food to meet the requirements of increasing demand for agricultural commodities (Godfray et al., 2010; Foresight, 2011). However, a recent report (Moorhouse et al., 2009) has suggested that at least 30% of the practices that aim to minimize the environmental impact of livestock systems

may be inconsistent with animal welfare. This has led to the suggestion that there may be a trade-off between reduction of environmental impact and enhancement of animal welfare in livestock systems. Such conflicts may arise from changes in stocking density, as was the case for both the broiler and egg production systems considered here, an increase in heat inputs to maintain housing temperature and perhaps an increase in food intake. All these will be associated with an increase in inputs and use of resources per unit of product. On the other hand, less intensive systems of production, like the ones considered here, may be associated with a lower incidence of disease (Bennett, 2003), which may result in better feed conversion efficiency (Sandberg et al., 2006, 2007) and reduction in mortalities. Therefore, the trade-offs between reduction in environmental impact and enhancement of animal welfare may not be as severe as was previously thought (Moorhouse et al., 2009). This view is supported by the outcome of the present study. Adoption of a new system of production that requires the installation of new equipment (such as the heat exchangers) or other changes in the housing would impose additional economic costs (e.g., Zhao et al., 2013). Although we have not performed an economic comparison between the alternative systems considered here, it is possible that such costs may be offset by the price premium commanded by enhanced-welfare products. These considerations are beyond the scope of our paper.

Conclusions The results of this study suggest that alternative chicken systems that aim to enhance bird welfare can have the same or lower environmental impact as conventional systems of production, at least when the feed conversion ratio of the birds is not significantly increased and when modern energy efficient housing systems are applied. The introduction of alternative systems, such as colony cages, was met by some skepticism by the poultry industry within the European Union, mainly because the consequences of the new systems on the production and environmental impacts were unknown. The outcomes of our analyses should offer some reassurance to the industry about such consequences of alternative poultry systems.

ACKNOWLEDGMENTS This research was financially supported by Aviagen Ltd. (Newbridge, Midlothian, UK), DSM Nutritional Products Ltd (Heanor, Derbyshire, UK), Harbro Ltd. (Turriff, Aberdeenshire, UK), Moy Park Ltd. (Sleaford, Lincolnshire, UK), National Farmers’ Union (Stoneleigh Park, Coventry, Warwickshire, UK), Noble Foods Ltd. (Bilsthorpe, Newark, UK), O’Kane Poultry Ltd. (Ballymena, UK), The Soil Association Ltd (Bristol, UK), and Waitrose Ltd. (Bracknell, Berkshire, UK) with match funding from Defra (London, UK), through


GWP, the total CV of the standard UK broiler production is about 10% and in the cage egg production about 7%. These uncertainties are clearly higher than the observed differences between the systems in the present study. This superficially suggests that there may be no significant differences between the old and new systems in the environmental impact categories such as GWP.

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the Sustainable Livestock Production LINK program, Department of Agriculture and Rural Development Northern Ireland (Belfast, UK), and the Scottish government (Edinburgh, UK).

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APPENDIX Details of the Structural Model The structural model calculated all of the inputs required to produce the functional unit, allowing for breeding overheads (3 generations of breeding stock), mortalities, and productivity levels. It also calculated the outputs, both useful (broiler meat, layer meat, eggs) and unwanted. Changes in the proportion of any activity had to result in changes to the proportions of others to keep producing the desired amount of output. Establishing how much of each activity (i.e., subsystem, for example, breeding, hatching, and pullet rearing) was required was found by using linear equations that described the relationships that linked the activities together. The general structure of the model was based on multiple linear equations, which were solved simultaneously using Visual Basic for Applications. The solution was the amount, X (for example the number of birds),

of each activity, i that produced the desired amount of output Z (e.g., broiler meat or eggs), n

Z = ∑ z i X i , [A1]

i =1

where zi is the output of activity i, and also satisfies the set of flows between activities:

n

∑ cij Xi

= 0, j = 1...p, [A2]

i =1

where cij is the supply or demand of j by activity i. Demands are negative and supplies are positive, and total supply must equal total demand. For example, the supply of chicks from hatcheries must equal the demand of birds in the rearing system (and allow for mortalities). The total amount of material k flowing into the system was

n

M k = ∑ mik X i , k = 1...q, [A3] i =1

where mik is the flow of material k into activity i. The LCI for the system was the total of each burden l:

p

Bl = ∑ M k bkl , l = 1...r , [A4] k =1

where bkl is the amount of burden l produced by the use or disposal of material k and Mk is the total amount of material. The LCI also identifies the contribution of each material,

Bkl = M k bkl , [A5]

or activity,

q

Bil = X i ∑ mik bkl . [A6] k =1

The structure of the model was such that changes could be made whether a parameter value was derived empirically or was linked to another model. A central feature of the model was the connection to a mechanistic submodel, which linked together bird growth, food intake, and excreta composition thus utilizing the empirical data provided by the industry.

Further Details of the Arable Model and Data The basic approaches to crop modeling are described by Williams et al. (2006) and Williams et al. (2010), but additional details are presented here.


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model includes a potential for aquatic or terrestrial eutrophication, or both, and is taken from Heijungs et al. (1992). The calculation is based on quantifying the potential contribution of phosphate and species of N to biomass formation. Most poultry farms buy most feed in, so that a delivery distance of 250 km for feeds was assumed. The calculation of a manure credit through the fertilizer value of N was derived using winter wheat. This is the most widespread feed crop grown in the United Kingdom and has the most quantified yield response to N. It is thus the most robust crop on which to make this type of assessment.

Emissions from Land Use Changes According to a widely accepted carbon footprinting method, PAS 2050 (BSI, 2011), the direct GHG emissions resulting from recent land use change (LUC) associated with crop production must be included in the carbon footprint of each crop (i.e., the sum of the GHG emissions per unit weight of crop). Most of the GHG emissions from LUC are as CO2 from loss of soil and biomass carbon. Recent LUC is defined as 20 yr in PAS 2050 (BSI, 2011). This time period is arbitrary, given the nonlinear rates of change in soil carbon, but is considered to be a pragmatic value that covers the largest change and the time where the change is close to linear. The main land use changes that cause GHG emissions related to soya production are from forest or pasture (natural or managed) to arable land. The pasture is mainly Cerrado in Brazil and Pampa in Argentina (FAO, 2011). The PAS 2050 (BSI, 2011) also states, “Where the country of production is known, but the former land use is not known, the GHG emissions arising from land use change shall be the estimate of average emissions from the land use change for that crop in that country.” In this study, a weighted average for soy was derived from an analysis of land use and crop production statistics of the United Nations Food and Agricultural Organization (FAO, 2011). The data were analyzed to estimate to rates of change of types of land use and the degree of interchange between crops, in that some soy expansion is from existing arable land. This was used to estimate the proportions of soy grown on mature arable land and that converted from pasture, forest, or other land in Brazil and Argentina. The LUC emissions were written off over 20 yr for each unit area of land, as in Audsley et al. (2010). The annual rates of LUC emissions were taken from PAS 2050 (BSI, 2011). These were combined with the national yields of soy that were reported by FAO (2011) to obtain the LUC emissions per unit of soy. As the overall result of the analysis, the LUC effect of 1.3 kg of CO2e was included in the GWP per 1 kg of soy meal.


The production of seeds is implicitly included in the model. Seeding rates are deducted from gross yields, so that the burdens of production are quantified against net yields. Pesticide manufacturing data came from Green (1987); this was considered the latest data available in the literature. Pesticide use rates came from the UK official Pesticide Usage Survey. Fuel consumption for typical operations were derived in Williams et al. (2006) from a variety of published and industry data sources. These included adjustments for soil texture in the case of subsource operations. Sets of field operations were developed for plough-based, reduced tillage, and direct drilling. These were based on experience of industry partners, literature, and the large distillation of arable practice that is in the Silsoe Whole Farm Model (http://www.cranfield.ac.uk/ research/research-activity/current-projects/researchprojects/silsoe-whole-farm-model.html). The proportions of tillage approaches were taken from government surveys, the UK Soil Management Initiative, and industry partners. In this study, the main crops included the diets were wheat, soy, oilseed rape, and sunflower. The net yields of these crops were 7.8, 2.2, 3.2, and 2.4 t/ha, respectively. For the soy production, data on the agricultural phase and in processing came from Cederberg (2002), Benton Jones (2003), Mortimer et al. (2003), Dalgaard et al. (2008), and da Silva et al. (2010), together with insights from the Ecoinvent 2 database. Allocation between the main constituents of soy used economic allocation to derive these factors for the partitioning of burdens of soy products: soy oil 37%, soy meal 61%, and soy hulls 2%. Ammonia emission factors applied in the model were taken from the Inventory of Ammonia Emissions from UK Agriculture (2012). Nitrate leaching for UK crops was derived from the simulation model SUNDIAL, as described in Williams et al. (2006). A simplified, nonspatial approach to phosphate emissions was taken from UK national statistics as described in the Defra-funded project Environmental Benchmarks of Arable Farming (http://tinyurl.com/Defra-ES0112). Nitrous oxide emission factors were the Tier 1 IPPC (2006) values. Nitrogen dynamics in rotations were quantified with the SUNDIAL simulation model, which was run until a steady state was established, such that the N pools at the start and end of a rotation are the same. This allowed long-term mass balances to be established for a range of crop rotation in which variations could be explored, such as straw incorporation and either increasing or decreasing N supply. These were applied across 3 soil textures and rainfall levels. Simplifying regressions were derived between N surpluses and N losses by denitrification and leaching. The P and K supplies were considered to be those needed to supply long-term offtake and losses and thus not deplete the soil of either element. The eutrophication potential calculated by the

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