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Abstract: Estimates of global greenhouse gases (GHG) emissions attributable to livestock range from 8 to 51%. This variability creates confusion among policy makers and the public as it suggests that there is a lack of consensus among scientists with regard to the contribution of livestock to global GHG emissions. In reality, estimates of international scientific organizations such as the International Governmental Panel on Climate Change (IPCC) and the Food and Agriculture Organization (FAO) are in close agreement, with variation mainly arising on how GHG emissions are allocated to land use and land use change. Other estimates involve major deviations from international protocols, such as estimated global warming potential of CH4 or including respired CO2 in GHG emissions. These approaches also fail to differentiate short-term CO2 arising from oxidation of plant C by ruminants from CO2 released from fixed fossil C through combustion. These deviances from internationally accepted protocols create confusion and direct attention from anthropomorphic practices which have the most important contribution to global GHG emissions. Global estimates of livestock GHG emissions are most reliable when they are generated by internationally recognized scientific panels with expertise across a range of disciplines, and with no preconceived bias to particular outcomes. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

Abstract: Numerous mitigation strategies are proposed to reduce greenhouse gas (GHG) emissions from ruminants, with many aimed at reducing enteric CH4. Before implementing such practices, it is critical to evaluate their net impact on total farm GHG emissions. Thus, a life cycle assessment (LCA) was conducted using HOLOS (i.e., a whole farm model based on Intergovernmental Panel on Climate Change methodology modified for Canadian conditions that considers all significant CH4, N2O and CO2 emissions from the farm) to establish whole farm GHG emission intensity for beef production in western Canada (i.e., baseline scenario) as affected by various mitigation practices. Mitigation practices were applied to the baseline scenario and their impacts on the intensity of GHG emissions assessed. Mitigation practices included dietary modifications aimed at reducing CH4 emissions (i.e., changed forage use levels, dietary supplementation with polyunsaturated lipids, use of corn distillers dried grains, improved forage quality) and improved animal husbandry (i.e., increased longevity of breeding stock, improved reproductive performance of the herd). The simulated farm was a beef production operation comprised of 120 cows, 4 bulls, and their progeny, with the progeny fattened in a feedlot. The farm also included cropland and native prairie pasture for grazing to supply the feed required by the herd. The LCA was conducted over 8 years to fully account for lifetime GHG emissions from breeding stock, as well as the progeny raised for market. The baseline scenario estimated the GHG emission intensity of beef production at 22kg CO2 equivalent/kg carcass; 80% of GHG emissions were from the cow calf system and 20% from the feedlot system, with enteric CH4 accounting for 63% of total emissions. Strategies applied to the cow calf herd individually reduced total farm GHG intensity by up to 8% with up to a 17% total reduction possible by combining strategies. In comparison, strategies applied to the feedlot had only a small impact on GHG emissions; reducing total GHG intensity by less than 2% when applied individually or by 3–4% when applied in combination. Although the North American beef production system is already highly efficient, a number of mitigation strategies could be implemented to further lower GHG emissions associated with producing beef, with a total reduction of about 20% attainable if multiple strategies are applied to both the cow herd and the feedlot. However, the biggest reductions in GHG emissions are achieved when mitigation practices target reducing enteric CH4 from the breeding herd. When the grassland in the baseline scenario was newly seeded onto previously cropped land, its soil C gain more than offset all GHG emissions, changing the beef production system from a net emitter to a net sink of C. Although such estimates of soil C gain have uncertainty, this scenario demonstrates that the net GHG balance of a beef production system is powerfully influenced by C dynamics in the associated land base, emphasizing the importance of including these dynamics in assessments of mitigation potential. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

Abstract: The Australian dairy industry contributes ∼1.6% of the nation''s greenhouse gas (GHG) emissions, emitting an estimated 8.9 million tonnes of CO2 equivalents (tCO2e)/annum (). This study examined GHG emissions of 60 Tasmanian dairy farms using the Dairy Greenhouse gas Abatement Strategies (DGAS) calculator, which incorporates International Panel on Climate Change (IPCC) and Australian inventory methodologies, algorithms and emission factors. Sources of GHG emissions including pre-farm embedded emissions associated with key farm inputs (i.e., grains/concentrates, forages and fertilizers) and on-farm emissions from CO2, CH4 and N2O are estimated by DGAS software. A detailed description of GHG calculations and functionality of DGAS software are provided. Total farm GHG emissions of 60 Tasmanian dairy farms, as estimated with DGAS, ranged between 704 and 5839tCO2e/annum, with a mean of 2811tCO2e/annum. Linear regression analyses showed that 0.93 of the difference in total farm GHG emission was explained by milk production. The estimated mean GHG emission intensity of milk of production was 1.04kgCO2e/kg fat and protein corrected milk (FPCM; ranged between 0.83 and 1.39tCO2e/tFPCM) with a standard deviation of 0.13. Stepwise multiple linear regression analysis showed that feed conversion efficiency (kgFPCM/kgdry matter (DM) intake) and N based fertilizer application rate explained 0.60 of the difference in the GHG emissions due to milk production from these pastoral based dairy systems. Estimated per cow and per hectare emission intensity was 6.9±1.46tCO2e/cow and 12.6±4.37tCO2e/ha, respectively. Stepwise multiple linear regression analysis showed that DM intake per cow (tDM intake/cow/lactation) explained 0.86 of the variability in per cow GHG emissions intensity, while milk production/hectare (tFPCM/ha) explained 0.92 of the variability in per hectare GHG emission intensity. Given the influence that feed conversion efficiency and/or N based fertilizer application rates had on all GHG emissions intensities, it is clear that these factors should be key target areas to lower the intensity of emissions associated with dairying in Tasmania. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

Abstract: Swine manure storage is a source of greenhouse gas (GHG) emissions. This study was conducted to quantify CO2, CH4 and N2O emissions from swine manure stored at different stack heights using dynamic emission vessels. Stack heights of 10, 20, and 40cm to cover the typical range of manure stack heights, were examined at 25°C with a ventilation rate of 20air changes/h with each regimen replicated thrice. Results show that the GHG emissions increased on the 2nd to 3rd day of manure storage then decreased to became stable after 10d of storage. Manure stack height affected GHG emissions from stored swine manure, with the lower stack height having higher CO2 and N2O, but lower CH4, emissions/kg of initial manure weight. On the basis of 100yr global warming potential for CH4 and N2O, cumulative emissions were 7.5±1.11, 6.8±1.32 and 10.8±1.23g CO2-eqv/kg initial manure, respectively, for the 10, 20, and 40cm stacks over the 6wk storage period. Results suggest that 20cm stack height produced the least GHG emissions. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

Abstract: The strategy for New Zealand dairy farming () formulates targets for increased national milk production and a reduction in greenhouse gas (GHG) emissions, but acknowledges these two targets conflict because GHG typically increase with increased milk output. Our objective was to determine if both targets could be achieved by implementing combinations of five mitigations. A farm scale computer model, which includes a mechanistic cow model, was used to model a typical pasture based New Zealand dairy farm as the baseline farm. The five mitigations were: (1) improved reproductive performance of the herd resulting in lower replacement rates, (2) increased genetic merit of the cows combined with lower stocking rate and longer lactations, (3) keeping lactating cows on a loafing pad for 12h/day for 2 mo during autumn, (4) growing low protein crops of grains and/or silages of maize, barley and oats on a portion of the farm and feeding this to lactating cows, (5) reducing fertilizer N use and replacing some of this with nitrification inhibitors and the plant growth stimulant gibberellins. No single mitigation strategy achieved both targets of increasing production by 10–15% and reducing GHG emissions by 20%, but when all were simultaneously implemented in the baseline farm, milk production increased by 15–20% to 1200kg milk fat+protein/ha, and absolute GHG emissions decreased by 15–20% to 0.8kg CO2-equivalents (CO2-e)/kg fat and protein corrected milk (FPCM), which is equivalent to a decrease from 11.7 to 8.2kg CO2-e/kg fat+protein. The synergies of the mitigations resulted in reduced dry matter intake and enteric CH4 emissions, a reduction in N input and N dilution in feed, and, therefore, reduced urinary N excretion onto pastures, and an increase in feed conversion efficiency (i.e., more feed was used for production and less for maintenance). Mechanistic CH4 models as part of farm scale models are important because current GHG inventory methodology cannot properly evaluate CH4 emissions for a range of potential mitigation strategies. There is also a need to develop capabilities in farm scale models to accurately simulate urine patches and N2O emissions from these patches. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

Abstract: The efficacy of technologies to reduce enteric CH4 emissions from ruminants are typically evaluated on individual animals with little consideration of enterprise scale impacts. While impacts of the many rumen manipulations being studied are hard to anticipate, there is adequate information to assess impacts of farm management changes and potential animal genetic changes on whole farm productivity and enteric CH4 emissions. Seven common sheep production systems grazing an annual pasture in central New South Wales, Australia, were modelled using GrassGro® (version 3.1.2). A range of animal management and animal genetic strategies were examined for their impact on total enteric emissions, emission intensity (i.e., kg CO2 equivalent/kg live weight (LW) of animal sold) and profit. Within enterprises, mitigation options were compared at their respective sustainable economic optimum stocking rate as it was assumed that farmers would seek to achieve the highest sustainable profit achievable from a finite land resource. Management options considered were choice of lambing time, mating ewes for the first time as lambs rather than yearlings, and feeding lambs to reduce time to slaughter. The potential for using selective animal breeding was also tested, with sheep physiological parameters being altered in GrassGro® to represent genetic improvement in fecundity, LW gain, residual feed intake and CH4 yield. In general, the management choices delivering lowest emission intensity were also the most profitable within sustainability constraints. Mating maiden ewes as lambs was only effective in reducing enterprise emissions intensity in self-replacing flocks (i.e., no purchased replacements). When stocking rates were at the sustainable economic optimum, choice of enterprise or management had little influence on total enteric emissions from the enterprise. If decisions are guided solely by economics, farmers are likely to continue with similar levels of production (and emissions) until a price on enteric CH4 emissions makes the sheep enterprise unprofitable, or an alternative more profitable enterprise than sheep grazing emerges. Improving animal genetics for residual feed intake or CH4 yield offers opportunity to reduce enterprise emissions, but industry progress toward higher genetic merit for these traits is expected to be slow due to relatively low heritability and competing economic imperatives for progress in other traits. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

Abstract: Humanity is quickly encroaching upon the finite limits of the biosphere. As our numbers and appetites grow, food supplies become less secure, reserves of clean energy dwindle, pools of freshwater evaporate, the atmosphere''s capacity to absorb our emissions diminishes and space for human and biotic habitat grows scarce. In response, some are now asking whether the biosphere can support our growing herds of domesticated livestock, notably ruminants. My aim in this review is to contemplate the place of these animals in a world in need of re-greening, in more ways than one. In addressing this objective, I advance the premise that the place of livestock is examined best from the vantage of ‘land’, broadly defined. Livestock have been implicated in many injurious processes: land use change, excess water use, nutrient excretion, fossil energy use, competition for food and emission of greenhouse gases. At the same time, they offer numerous benefits: producing food from human inedible sources, preserving ecosystem services, promoting perennials on croplands, recycling plant nutrients and providing social benefits. Thus livestock can be both stressors and benefactors to land and the aim of researchers should be to shift the net effect from stress to beneficence. To advance this goal, I offer seven questions, seen through the lenses of ‘systems’, ‘place’, ‘time’ and ‘community’, mostly to foster discourse. How do we better study whole systems? How do we better tune the systems to local land? How can we know long term consequences? How do we measure progress? How do we choose among trade-offs? How do we engage society? What will (or should) our successors’ livestock systems look like? Humans and their livestock are intertwined to such an extent that their symbiosis will not likely soon be severed. Livestock offer many benefits to human society and often their place in ecosystems can be ecologically justified. But that does not mean that all ways of raising them are beneficial, nor that they necessarily fit everywhere. In coming decades, researchers, in concert with practitioners, consumers and policymakers, will need to show creativity, foresight and courage to envision new ways of melding animals into our ecosystems, not only to minimize harm, but to advance their re-greening. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

Abstract: The requirement to rapidly and efficiently evaluate ruminant feedstuffs places increased emphasis on in vitro systems. However, despite the developmental work undertaken and widespread application of such techniques, little attention has been paid to the incubation medium. Considerable research using in vitro systems is conducted in resource-poor developing countries that often have difficulties associated with technical expertise, sourcing chemicals and/or funding to cover analytical and equipment costs. Such limitations have, to date, restricted vital feed evaluation programmes in these regions. This paper examines the function and relevance of the buffer, nutrient, and reducing solution components within current in vitro media, with the aim of identifying where simplification can be achieved. The review, supported by experimental work, identified no requirement to change the carbonate or phosphate salts, which comprise the main buffer components. The inclusion of microminerals provided few additional nutrients over that already supplied by the rumen fluid and substrate, and so may be omitted. Nitrogen associated with the inoculum was insufficient to support degradation and a level of 25mgN/g substrate is recommended. A sulphur inclusion level of 4–5mgS/g substrate is proposed, with S levels lowered through omission of sodium sulphide and replacement of magnesium sulphate with magnesium chloride. It was confirmed that a highly reduced medium was not required, provided that anaerobic conditions were rapidly established. This allows sodium sulphide, part of the reducing solution, to be omitted. Further, as gassing with CO2 directly influences the quantity of gas released, it is recommended that minimum CO2 levels be used and that gas flow and duration, together with the volume of medium treated, are detailed in experimental procedures. It is considered that these simplifications will improve safety and reduce costs and problems associated with sourcing components, while maintaining analytical precision. [Copyright &y& Elsevier]