Management options to reduce the carbon footprint of livestock products

Management options to reduce the carbon footprint of livestock products John E. Hermansen and Troels Kristensen University of Aarhus, Faculty of Agricultural Sciences, Department of Agroecology and Environment, Research Centre Foulum, PO Box 50, DK-8830 Tjele, Denmark Implications Livestock products carry a large carbon footprint compared with other foods, and thus there is a need to focus on how to reduce it. The major contributing factors are emissions related to feed use and manure handling as well as the nature of the land required to produce the feed in question. We can conclude that the most important mitigation options include Key words: land use, manure handling, feed conversion, life cycle assessment, climate Introduction better feed conversion at the system level, use of feeds that increase soil carbon sequestration versus carbon emission, ensure that the manure produced substitutes for synthetic fertilizer, and use manure for bio-energy production. Basically, it is important to make sure that all beneficial interactions in the livestock system are optimized instead of focusing only on animal productivity. There is an urgent need to arrive at a sound framework for considering the interaction between land use and carbon footprints of foods. The human impact on global warming is related to our consumption, and thus attempts are made to quantify the relation between our consumption of different products and the impact on global warming. Life cycle assessment (LCA) provides a systematic way to quantify the environmental impacts of products or services from cradle to grave, thus allowing estimation of the environmental impacts related to the consumption/use of different products. At the same time, this tool can efficiently be used to identify hot spots and, thereby, improvement options in relation to environmental impacts associated with a certain product. Recently, there has been a boost in the mutual interest from business and policy in LCA approaches exacerbated by the concern about global warming. It is generally agreed that LCA is an appropriate tool to address 2011 Hermansen and Kristensen. doi:10.2527/af.2011-0008 this issue instead of more partial tools such as food miles. This is important because within the agriculture and food sector, emissions other than CO 2 related to energy for transport are often more important considering their contribution to the total impact on global warming. Thus, emissions of N 2 O or CH 4 are often the most important contributors to global warming. In LCA these impacts are aggregated in CO 2 equivalents (CO 2 eq.), which are often referred to as carbon footprint, taking into account their different contribution to global warming. At the request of the European Union Commission, Tukker et al. (2006) identified those products or services with the greatest environmental impact throughout their life cycle from cradle to grave. The overall conclusion was that 3 areas, food (and drink), private transport, and housing, each were responsible for 20 to 30% of the total environmental impact of the overall consumption of citizens in the European Union. Further, Weidema et al. (2008) estimated that the consumption of meat and dairy products was responsible for 14% of the total global warming resulting from the consumption of all kinds of products and services (e.g., food, transportation) within the 27 European Union member countries. The growing demand for livestock products following the improvement in the standard of living in many places around the world highlights the importance of addressing this issue. However, whereas a sound methodology exists to analyze improvement possibilities from a food-chain perspective, a number of methodological choices affect the results of the analysis. The dual purpose of this paper is to point out management options to reduce the carbon footprint of livestock products from a life-cycle perspective and to clarify how the effects of some of these options are affected by the type of analysis used. Factors Influencing Carbon Footprint in Livestock Products at the Farm Gate The farming stage is crucial in determining the carbon footprint of most foods because as much as 70 to 90% of the emissions in the total chain occur before the products leave the farm gate. In Figure 1 we illustrate the main aspects to take into account when estimating the carbon footprint of a product. Before the farm gate, emissions related to the production and transport of inputs to the farm need to be established. At the farm, major emissions take place related to the internal turnover at the farm. Methane is produced during enteric fermentation and during storage of manure and needs to be estimated based on total feed use and composition as well as storage conditions for the manure. The emission of N 2 O is related to application of manure and artificial fertilizer to the field as well as nitrate and ammonia losses during and after the growing season. Carbon dioxide is produced following combustion of fuel. Further change in soil carbon content might also contribute to emission of CO 2, but the net effect is very dependent on the actual production and the approach used for calculation of the carbon footprint, as illustrated later. July 2011, Vol. 1, No. 1 33

Figure 1. Illustration of life cycle assessment of livestock products in the chain toward the supermarket with special focus on the agricultural part of the chain. Huge differences in the carbon footprint of different foods exist. Thus, Mogensen et al. (2009) reported differences ranging from 0.1 to more than 20 kg of CO 2 eq. per kilogram of food ready at the retailer. De Vries and de Boer (2010) compared different livestock products in more detail in a review of recently published results. Beef, with a range of 15 to 32 kg of CO 2 eq. per kilogram of product, had the largest carbon footprint followed by pork (4 to 11 kg of CO 2 eq.) and chicken (4 to 6 kg of CO 2 eq.), and this ranking was the case irrespective of whether it was expressed per kilogram of product, per kilogram of protein, or per typical daily intake in Europe. Milk had the smallest carbon footprint of the investigated livestock products per kilogram, but when considered per kilogram of milk protein, it was equivalent to chicken. The huge difference in published results of carbon footprint is partly a reflection of different production systems, but it is reflective of the complexity of livestock systems as well. This complexity requires a number of assumptions to perform an LCA. Some of the most important aspects are 1) the way or the degree to which the rearing of the farm animals is integrated in the land use and how this is accounted for; 2) the impact of different housing and feeding conditions; 3) the multi-process and multi-product nature of livestock production systems and how these are accounted for; and 4) the challenge in estimating emissions related to livestock production, which seldom can be performed though direct measurements. Some of these aspects are highlighted in the following for pork, beef, and milk systems. Pork The main contributors to the carbon footprint of pork for typical pig farming systems in Northwest Europe was found to be N 2 O, mainly related to feed production, followed by CO 2, from energy use, and CH 4, from manure handling (Nguyen et al., 2010a). In terms of processes, the results from a recent Danish investigation are shown in Figure 2. Feed use was the dominant contributor responsible for 55% of total emissions. On-farm emissions, which include enteric CH 4 emissions, CH 4 O emissions from in-house manure and outside storage, O emissions from manure application, were the second most important contributor, accounting for 41% of total emissions. Transport of all items associated with the system and energy use in housing and manure management accounted for only 8 and 6%, respectively. Thus, when considering reduction possibilities, the contribution from feed use is crucial. It appears from Figure 2 that the 25% of Danish pig herds with greatest technical efficiency in pig rearing (expressed by piglets weaned per sow and feed 34 Animal Frontiers

Figure 2. Contribution to the carbon footprint of pork from different processes. This is exemplified by average Danish production and the quartile of herds with greatest technical efficiency, kilograms of CO 2 equivalents per kilogram of pork (after Nguyen et al., 2011). use per kilogram gain in the fatteners) produced pork with 10% less carbon footprint than pork produced from the average herd (Nguyen et al., 2011). However, when comparing different systems, feed composition may also differ, and in this respect the estimation of the carbon footprint of the different feeds becomes equally important, and this is complex and a matter of dispute. Two aspects are of particular importance: the definition of the feed used and how changes in soil carbon stocks related to feed production are taken into account. Mainstream pork production is to a large extent based on feed brought in to the farm, and even if some feed items are produced at the farm they might be interchanged with other feed. In that sense one might say that the pork production is a global business drawing primarily on globally traded feed resources. Consequently using more feed (producing one more pig) ultimately requires more soybean meal and cereal, independent of the actual detailed composition of the feed mix. It is well established that soybean meal and cereal are the marginal feedstuffs for monogastrics (Bouwman et al., 2006; Schmidt, 2010). In terms of LCA, one might then express the feed use in cereal and soybean equivalents and mineral requirements as a basis for establishing the carbon footprint using published results for these items (Dalgaard et al., 2008; Schmidt, 2010). We argue that this, which we call a marginal approach, is a valid method that at the same time allows comparison among different studies. However, the dominant approach currently used in LCA is an attributional approach based on an estimate of the carbon footprint of each individual feed item used (De Vries and de Boer, 2010). This approach is supported by the Public Available Specification (called PAS 2050) for documenting the carbon footprint of a product, which is developed in cooperation with the British Standard (BSI, 2008). Given the importance of feed for the total carbon footprint of pork, it is very crucial to have transparent assumptions on this issue when considering results from different studies. Another aspect is how to handle changes in carbon stocks in soil and vegetation related to land use, which in turn affects the carbon footprint of the feed. This is important when estimating impacts related to expansion of land use for soybean production, but also when analyzing pork systems that differ in their requirements for land, which is the case when comparing organic and conventional pork production. Organic pig production is typically characterized by allowing pigs to have access to grassland in opposition to conventional production systems. Halberg et al. (2010) compared organic and conventional pig production. When ignoring changes in soil carbon, the greenhouse gas emission per kilogram of body weight pig in the organic system was 7 or 22% greater than in conventional pig production for only sows, or sows plus finishers on grassland, respectively, due to larger feed use and greater N 2 O emissions as a result of an overall greater nitrogen turnover in the system. When the carbon sequestration on the farm was included, the net greenhouse gas emissions was reduced by approximately 0.4 to 0.6 kg of CO 2 eq. per kilogram of body weight pig in the organic systems, a reduction of approximately 11 to 18%. Thus, when including soil carbon sequestration, the greenhouse gas emissions per kilogram of pig from the organic indoor fattening system was less than from conventional pig systems, where the net carbon changes were close to neutral. Emissions related to manure handling is another major contributor to the total carbon footprint of pork. The emissions related to manure handling depend on a number of conditions, such as storage time and temperature in different compartments, influencing CH 4 O emissions. The methane emission from the slurry in the housing section, for example, is very much dependent on storage time (IPCC, 2006), and an indoor (stable) storage period of more than 1 month can affect the total global warming potential by approximately 0.5 kg of CO 2 eq. per kilogram of body weight in a temperate climate compared with a short indoor storage period. Under cooled conditions the impact will be smaller, whereas under warm conditions the impact will be larger. Thus, it is very important in practical pig farming to take these factors into account to reduce the carbon footprint of pork. To a varying degree, the manure produced substitutes for synthetic fertilizer of nitrogen and phosphorus for crop production, thus saving resources. Nguyen et al. (2010a) found that at a substitution rate of nitrogen of approximately 45% or less, the value of the manure in relation to global warming was zero or negative. With a realized substitution rate for nitrogen of 75%, the value of the manure reduced the environmental impact of pork by approximately 13%. This highlights the importance of manure management in pig production, and the practical interpretation from a carbon footprint point of view would be to ensure a greater utilization rate of the manure produced by pigs, because this production is responsible for, and can benefit from, it. Another option is to use the manure for biogas production before its utilization as a fertilizer. The impact is threefold: 1) substitution of the energy produced for energy that would otherwise be produced from fossil fuels, 2) reduction of CH 4 O emissions during subsequent storage and manure application, respectively, and 3) an increased substitution rate of synthetic fertilizers. Nguyen et al. (2010a) found that the carbon footprint of pork was reduced by 27% by implementing this technology. Thus, policy measures to stimulate such a development may contribute substantially to a reduction in the carbon footprint from meat consumption. These results imply that the largest scope for improvement at the farm level lies in reducing feed use, reducing emissions related to manure handling, ensuring that the nutrients in manure substitute for synthetic fertilizer, and utilizing manure for biogas production. Beef Apart from the beef originating from culled dairy cows, 2 main categories exist: beef produced in suckler systems, where suckler calves July 2011, Vol. 1, No. 1 35

are reared with their mother for an extensive period (beef cattle systems) followed by a fattening period, and beef produced from bull calves primarily from dairy herds and reared in specialized fattening units. Beef cattle systems are traditionally based on pasture in less productive areas and relatively low feeding intensity compared with the more intensive feeding of bull calves in dairy production. This, and the fact that the feed requirement of the mother cows has to be accounted for, result in a greater dry matter intake per kilogram of beef produced in such systems (Casey and Holden, 2006; Verge et al., 2008). This in turn leads to a greater carbon food print of the beef from the extensive pasture-based systems (Cederberg et al., 2009; Veysset et al., 2010), with methane accounting for 60 to 70% of the total carbon footprint. In more intensive grain-based feeding system, the methane emission is less due to a greater digestibility of the feed and because a much smaller portion of the feed is used for maintenance (Peters et al., 2010). However, as mentioned, it is difficult to judge results obtained across studies due to different assumptions used in the LCA. Thus, Nguyen et al. (2010b) investigated the environmental profile of 4 different beef production systems, 1 beef cattle system and 3 systems based on dairy bull calves, which illustrates the main topics for beef production. The 3 categories of dairy based beef production were 1) bull calves, reared indoors on concentrates and slaughtered at an age of 12 months; 2) bull calves, reared indoors on a mixed ration of grass silage and concentrates and slaughtered at an age of 16 months; and 3) steers, fattened on a 40:60 mix of outdoor grazing and indoor feeding of grass silage and concentrates and slaughtered at an age of 24 months. It was further assumed that silage was produced on very productive grassland, that steers grazed on moderate productive grassland, and that beef cattle cows grazed on low productive grassland. All cereal and roughage was grown within the system, whereas the supplementary protein feeds were covered by imported soybean meal. The carbon footprint and requested land use under a number of assumptions regarding CO 2 emissions related to land use (some well accepted and some more hypothetical) is given in Table 1. Excluding impacts from estimated soil carbon changes on direct land use or impacts related to land use, changes resulted in a carbon footprint per kilogram beef ranging from 12.2 to 26.8 kg of CO 2 eq. depending on systems. The leading contributors to the carbon footprint for all systems were direct CH 4 O emissions (48, 55, 78, and 72% for young bulls, medium bulls, steers, and beef cattle systems, respectively). Including soil carbon changes from the direct land use narrowed this range because the carbon footprint from steers was reduced, whereas the opposite was the case for intensively reared bull calves. In fact, in that case relatively small differences occurred among the dairy-based systems. Thus, a fair comparison needs to take into account the impact of changes related to changes in soil carbon stocks as influenced by the system. Other land-related impacts, however, can be considered as well. Thus, PAS 2050 (BSI, 2008) suggests that CO 2 emissions related to land use changes initiated by the use of soybean meal should be taken into account. If so, it appears that the carbon footprint of bull calves from the dairy systems would be similar to that of the calves from the beef cattle system, whereas the carbon footprint of beef from steers would be least. Although there are good reasons to consider this aspect, acknowledging that carbon emissions from land use change, especially deforestation, are believed to be a significant contributor to climate change, accounting for 20 to 25% of total anthropogenic emissions during the 1990s (IPCC, 2000), the methodology suggested seems far from perfect. One might, following the same logic, reason that all land requested represents an opportunity to sequester carbon to a greater degree than by using it for beef production. No coherent rationale is yet presented for taking this issue into consideration, but it can be foreseen that this will happen in the future and greatly increase the carbon footprint of beef. Nguyen et al (2010b) illustrated the impact of different assumptions (Table 1). If all cereal land were considered as having opportunity cost for carbon sequestration through transferring it to woodland, the beef from bulls from the dairy system would have a greater carbon footprint than beef from bulls from the beef cattle system. If, on the other hand, the productive grassland was also considered as having opportunity cost for carbon, the greatest emission would be from steers coming from the dairy system. Although not exclusively important for beef production, the matter of land use per se is a matter of concern and will have consequences for the carbon profile of beef due to the relatively high land requirements. It seems from our point of view most reasonable that in the future opportunity costs will be taken into account for land areas that represent an opportunity to produce other foods. Low productive grassland with no alternatives, or grassland that from a societal point of view is dedicated to maintaining a particular cultural landscape, should not be burdened with opportunity costs. This would, however, be the case for use of land that could be used equally well for other purposes. In such a situation, beef from the beef cattle system and steers from the dairy system may be as competitive as intensively reared bull calves from the dairy system. The methane emissions related to rumen fermentation are a very important contributor to the carbon footprint of beef. Thus, reducing this will impact the carbon footprint. However, whereas measures are well documented, such as fatty acids in the diet and probably ionophores, it is difficult to see how the effect will be obtained in practice, and probably in some cases the effect may be overruled by the impact related to land use. Dairy The FAO recently reported a global average carbon footprint of 2.4 kg of CO 2 eq. per kilogram of milk, of which 93% was emission from cradle to farm gate (FAO, 2010). Emissions per unit of milk product vary greatly among different regions and countries as illustrated in Figure 3. It appears that the carbon footprint was markedly reduced with increased milk production until 3,000 to 4,000 kg of milk per cow and year. The main reason for the greater carbon footprint at a low yield is due to a general low feed efficiency in these systems and that a larger proportion of feed is used for nonproductive purposes such as replacement stock, maintenance requirement, and draught power. A number of studies have been performed with highly productive dairy herds. A particular aspect has been to estimate the carbon footprints in organic and conventional production systems. The overall picture found was that no major systematic difference seems present (Cederberg and Flysjö, 2004; Thomassen et al., 2008; Kristensen et al., 2011), the reduced milk yield in organic systems being compensated by a greater overall system efficiency. This is in accordance with results by Van der Werf et al. (2009) who concluded that the contribution of production system to overall interfarm variability was generally low. The interfarm variability in carbon footprint from 67 Danish dairy farms is shown in Figure 4, showing large variations among conventional as well as organic farms. Kristensen et al. (2011) further identified, through factor analysis on the 67 farms, strategies focusing on high efficiency in the herd or reduced stocking rate, defined by kilograms of milk per hectare, 36 Animal Frontiers

Table 1. Comparative land use and carbon footprint of beef produced in different systems per kilogram of meat slaughter weight at the farm gate (after Nguyen et al., 2010b) Item Beef cattle systems Males from dairy herds Calf age at slaughter, month 16 12 16 24 (steers) Land use, m 2 year Land occupation, total 42.9 16.5 16.7 22.7 Grassland 36.9 0 2.0 18.2 Highly productive 6.8 0 2.0 8.3 Moderately productive 0 0 0 9.8 Low productive 30 0 0 0 Cropland 6.0 16.5 14.7 4.5 Cereals 5.94 12.39 11.48 4.50 Soy meal 0.05 4.11 3.25 0.04 Carbon footprint, kg of CO 2 eq. 1 per kg without land use consideration 26.8 12.2 14.7 22.0 Including carbon sequestration on direct land use 2 27.3 16.0 17.9 19.9 Including estimated CO 2 emission from land use change, soy 3 27.4 27.5 27.0 20.0 Including estimated CO 2 emission from opportunity costs of land use, cereal 3 44.0 62.2 59.1 32.6 Including estimated CO 2 emission from opportunity costs of land use, highly and moderately productive grassland 4 61.7 62.2 64.2 79.8 1 CO 2 eq. = CO 2 equivalents. 2 Carbon sequestration (soil carbon change): grassland highly and moderately productive, 1,910 kg of CO 2 eq. per ha; cereals, 3,080 kg of CO 2 eq. per ha; low productive grassland and other crops, 0 kg of CO 2 eq. per ha. 3 Land conversion (20 years): from forest to cropland 2.8 kg of CO 2 eq. per m 2 year 1. 4 Land conversion (20 years): from forest to grassland 2.6 kg of CO 2 eq. per m 2 year 1. as promising for reducing carbon footprint per kilogram of milk at the farm gate. The difference was 0.13 kg of CO 2 eq. per kilogram of milk between the top and bottom quartile of farms ranked by herd efficiency, where the main difference was a difference in milk to feed of 1.32 vs. 1.06 kilogram of milk per kilogram of dry matter intake. Similarly the low stocking rate farms obtained a carbon footprint of 1.04 kilogram of CO 2 eq. per kilogram of milk compared with 1.14 CO 2 eq. for the high stocking rate farms, illustrating that with a low stocking rate, it is easier to have a good resource utilization in the system. Figure 3. Relation between emission of carbon footprint of milk and milk yield per cow. Each dot represents a country (Gerber et al., 2011). FPCM = fat- and proteincorrected milk. Vellinga et al. (2011) concluded that a promising measure to reduce greenhouse gases from intensive dairy farms in the Netherlands was to reduce the replacement rates. This highlights the importance of a good herd health and reproductive performance that sometimes may be hampered with increased milk yield per cow and thus counteract a perceived effect when considering primarily an increased milk yield per cow as a measure to reduce the carbon footprint. The Interaction Between the Carbon Footprint of Milk and the Beef Produced from the Dairy Herd Within dairy production the major product is milk, but an important coproduct is beef. Different methods can be used to attribute the total emissions of each of those products, which in turn can have significant impact on the emissions related to milk. According to the recommendations within LCA (ISO, 2006), first it should be tried to divide the production into subsystems and calculate the carbon footprint separately. This, however, is not an option when considering beef from culled cows or calves in the dairy systems. Otherwise it is suggested to expand the systems, and in this case basically allocate the total emission to the dairy in the first place and then subtract the saved emissions due to the coproduct, here beef, or to allocate the emissions to milk and beef based on economic or physical relationships. Kristensen et al. (2011) illustrated the consequences of these assumptions for the carbon footprint of milk (Figure 5), and in addition estimated by regression analysis the contribution from milk and beef to the total farm carbon footprint. July 2011, Vol. 1, No. 1 37

will be more than counteracted by the shift in beef from dairy to beef cattle systems. This illustrates that it is important to be implicit with setting the boundaries for the analysis when investigating improvement options. Conclusion Figure 4. Distribution of carbon footprint per kilogram of milk in 67 Danish farms with organic or conventional production (Kristensen et al., 2011). CO 2 eq. = CO 2 equivalents; ECM = energy-corrected milk. Figure 5. Carbon footprint of milk and beef from Danish dairy herd under different assumptions of allocating emissions to beef and milk, per kilogram of milk and per kilogram of body weight at the farm gate (after Kristensen et al., 2011). CO 2 eq. = CO 2 equivalents. Allocating the carbon footprint according to the theoretical feed requirements for milk and beef, respectively, as suggested by IDF (2010), resulted in the smallest allocation to milk and thus the smallest carbon footprint of milk, whereas on the other hand an economic allocation resulted in the largest carbon footprint of milk. The model derived resulted in an intermediate value for carbon footprint of milk. Given the difficulties in establishing a well-accepted rationale for allocation between milk and beef, it is suggested that this derived value is a good proxy that could be used across studies. These considerations lead to the last issue to highlight. How will the environmental impact of the entire milk production system and its interaction with beef production change in the future? In most developed countries the number of dairy cows has been steadily decreasing, but total production has remained practically unchanged thanks to an increase in the milk yield per cow. But at the same time the number of beef cattle cows has increased to compensate for the decrease in beef from the dairy system. The dairy based beef production is thus foreseen to decline as a result of reduced number of dairy cows. The total effect of this on greenhouse gas emissions has not been investigated, but data presented here, and as reported in Weidema et al. (2008), suggest that the dilution effect on feed for maintenance connected to a greater milk yields per cow There is no reason to believe that the interest in carbon footprinting of livestock products will diminish in the near future. First, livestock products carry a high carbon footprint compared with other foods, and second, the demand for livestock products is increasing worldwide, highlighting the issue of how to reduce the carbon footprint. Two aspects are important: reducing emissions related to feed use, and reducing emissions related to manure handling. Obviously a reduced total feed use per kilogram of product produced is a mitigation measure, but equally important is to consider the carbon footprint of the different feeds and how this is affected by growing conditions including soil carbon sequestration. The latter means that grass-based systems may have an advantage. However, there is a need to obtain a better framework for including in the assessment how land use occupation and land use changes as a consequence of increased feed demand are taken into account. The prevailing view indicates that this will enlarge the carbon footprint. Regarding manure handling, 3 aspects need attention: 1) the emissions of methane during storage, 2) the potential savings connected to efficient use in crop production, and 3) the potential of using manure for bioenergy production. 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Bebin. 2010. Energy consumption, greenhouse gas emissions and economic performance assessments in French Charolais suckler cattle farms: Model-based analysis and forecasts. Agric. Syst. 103:41 50. Weidema, B. P., M. Wesnæs, J. Hermansen, T. Kristensen, N. Halberg, P. Eder, and L. Delgado. 2008. Environmental improvement potentials of meat and dairy products. Institute for Prospective Technological Studies, Sevilla, Spain. (EUR 23491 EN). About the Authors John E. Hermansen heads the interdisciplinary Farming Systems Unit at the Faculty of Agricultural Science at Aarhus University, Denmark, the goal of which is to identify developing possibilities for farms in relation to societal expectations and paying attention to the satisfaction of the basic values of the farmer s family. The group includes expertise within animal science, plant science, and modeling. Development of life cycle assessment methodology is also a central part of the activities of the group, which hosts the LCA- FOOD database. John E. Hermansen has in the last year in particular researched new organic livestock farming systems of pigs and poultry in relation to sustainability issues and has headed a number of research and development projects in this area, and been involved in life cycle assessment of many types of agricultural products. Hermansen is vice president in the Livestock Farming Systems Commission, EAAP, and editor in chief of Livestock Science. Correspondence: John.Hermansen@agrsci.dk Senior Scientist Troels Kristensen is part of the Farming Systems Unit at Aarhus University and has broad experience with farming systems research based on studies at private farms, experiments conducted on private farms, and modeling. Different aspects of production, management, and environment issues in organic and conventional cattle farming have been the main working area, focusing on topics such as pasture management and grazing systems and the effects on product quality, leaching of nitrogen, and emission of climate gases. Troels Kristensen is highly experienced in design and analysis of on-farm data with respect to production, the economy, and the environment, working together with the Farmers Association and the dairy industry on these issues. The review magazine of animal agriculture July 2011: October 2011: January 2012: Issue Themes Fork to farm: The carbon footprint Guest Editor: Steven A. Zinn (University of Connecticut, Storrs, CT, USA) International trade and livestock production: Future prospects for the beef industry Guest Editor: Cledwyn Thomas (EAAP, Rome, Italy) and Dunixi Gabiña (Mediterranean Agronomic Institute of Zaragoza) Animal selection: The genomics revolution Guest Editor: Andrea Rosati (EAAP, Rome, Italy) July 2011, Vol. 1, No. 1 39