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Southeast Asia's human population is expected to rise by 100 million between 2023 and 2050, with an associated rise in animal-product output in the region's low- to middle-income countries. Countries with the largest population are forecast to continue their increasing poultry consumption, with regional pig meat consumption also to rise, but much less than in China to the north, and much less in Muslim-dominant countries. The forecast growth in the regional ruminant population is more modest and the farm-gate greenhouse gas (GHG) cost per unit of human food protein generated is much higher for ruminant meat (203–584 kg carbon dioxide equivalents (CO2e)/kg protein) than for pig meat (18 kg/kg) or poultry (4 kg/kg). Changing human diets away from ruminant or any animal-sourced protein, is being explored to increase the human food supply at a lower GHG cost. However, with small-holder livestock production systems dominant across many regional countries, the social, land-use and broader economic roles of ruminants need consideration. Strategies to expand ruminant production but with a reduced GHG unit cost (emission intensity) are being pursued. Increasing individual animal-product output, largely through simple animal health and nutritional management decisions, can allow future food targets to be met at a lower GHG emission than if this additional food was produced by business-as-usual livestock production systems. Because the Paris Agreement recognises the priority of food provision over emission abatement, it seems reasonable that much of Southeast Asia should pursue emission intensity targets more than absolute emission targets, and reflect this in their nationally determined contributions (NDCs). Emission-intensity intentions are already apparent not just in NDCs but in emerging carbon markets. Southeast Asia's forecast rise in human population and demand for animal-sourced food is likely to increase absolute greenhouse-gas emissions from the region's livestock sector. There are substantial animal and feed management opportunities to suppress the increase in these emissions by improving animal productivity. Targeting a regional reduction in emissions per unit animal product (emission intensity) instead of absolute emissions offers a means to support food security, while controlling emission of livestock derived greenhouse gases. This article belongs to the collection: SAADC 2023. [ABSTRACT FROM AUTHOR]

The Australasian dairy industry is facing the dual challenges of increasing productivity, while also reducing its emissions of the greenhouse gases (GHG) methane and nitrous oxide. Following the COP21 Paris Agreement, all sectors of the economy will be expected to contribute to GHG abatement. Enteric methane is the major source of GHG emissions from dairy production systems (>70%), followed by nitrous oxide (13%) and methane (12%) from animal waste, with nitrogen (N)-fertiliser use contributing ~3.5% of total on-farm non-carbon dioxide equivalent (non-CO2e) emissions. Research on reducing methane emissions from dairy cattle has focussed on feeding dietary supplements (e.g. tannins, dietary oils and wheat), rumen modification (e.g. vaccine, inhibitors), breeding and animal management. Research on reducing nitrous oxide emissions has focussed on improving N fertiliser efficiency and reducing urinary N loss. Profitable options for significant abatement on farm are still limited, with the industry focusing instead on improving production efficiency, while reducing emission intensity (t CO2e/t product). Absolute emission reduction will become an imperative as the world moves towards carbon neutrality by 2050 and, thus, a priority for research. However, even with implementation of best-practice abatement, it is likely that some residual emissions will remain in the foreseeable future. The soil organic carbon content of dairy soils under well fertilised, high-rainfall or irrigated permanent pastures are already high, therefore limiting the potential for further soil carbon sequestration as an offset against these residual emissions. The Australasian dairy industry will, therefore, also need to consider how these residual emissions will be offset through carbon sequestration mainly in trees and, to a more limited extent, increasing soil organic carbon. The Australasian dairy industry is facing the challenge of increasing productivity while also reducing greenhouse gas (GHG) emissions. This paper reviews the most promising technologies, concluding that substantial GHG abatement is possible, but the industry will need to consider further offsets in trees to achieve carbon-neutral dairy farming in Australia and New Zealand. [ABSTRACT FROM AUTHOR]

We investigated voluntary intake, growth and safety of cattle offered low-quality forage diets plus isonitrogenous molasses-based liquid supplements containing either urea (U) or a calcium nitrate-containing compound (NO3). We hypothesised that changing the nitrogen source from U to calcium nitrate would not jeopardise animal health or affect intake. Angus cattle (n = 24) were allocated to six pens, with three pens each receiving a molasses supplement containing U or a molasses supplement containing NO3 for 31 days. There was a trend (P = 0.06) for the NO3 treatment group to consume more of the (oaten chaff) basal diet than the U treatment group. The U group consumed more supplement than did the NO3 group (1.31 vs 0.40 kg DM/head.day s.e.m. = 0.094, P < 0.0001), but total DM intake was not different (6.45 vs 6.10 kg/head.day, P = 0.15). Mean final animal liveweight was not different between treatments. Methaemoglobin levels were higher in the NO3 group (2.1 vs 1.3%, P < 0.001). Low consumption of nitrate was also reflected in there being no effect of nitrate on the methane production rate when assessed in open-circuit calorimetry chambers (7.1 vs 7.0 g/head.2 h, P = 0.898). It is confirmed that nitrate may be safely provided to cattle when dissolved at 154 g/kg in a molasses-based liquid supplement available ad libitum , but may not be an effective methane mitigant due to low NO3 intake. It is speculated that nitrate may be a useful tool to limit voluntary intake of non-protein nitrogen supplements. Due to its significant impact on anthropogenic greenhouse gases, there is ongoing interest in reducing methane production from ruminants. Nitrate has been shown to reduce methane, but can also be deadly if too much is consumed, and the present study showed that intake is self-regulated at safe levels. However, intake is so low as to be minimally effective in reducing ruminant greenhouse gases. [ABSTRACT FROM AUTHOR]

There is a growing interest in forage mixtures (Diverse pasture; e.g. containing grasses, legumes and herbs), especially those with a greater tolerance of dry conditions and a decreased nitrogen (N) content (reducing N losses), compared with ryegrass (Lolium perenne L and Lolium multiflorum L)/white clover (Trifolium repens L) pastures (RyeWC), which dominate New Zealand pastoral systems for dairy production. However, the effect of alternative forages on enteric methane (CH4) emissions is not known. The objective of the present trial was to compare CH4 emissions and milk production from dairy cows grazing either mature RyeWC or mature Diverse pasture (both approximately with pasture mass of 5600 kg DM/ha). The Diverse mixture comprised ryegrass, white clover, lucerne (Medicago sativa L), chicory (Cichorium intybus L) and plantain (Plantago lanceolata L). Milk production, measured from cows commencing at ~162 days of lactation, was less when cows grazed RyeWC than Diverse pastures (15.4 vs 16.7 kg/day; P < 0.001), whereas CH4 production (g/day) was similar for the respective treatments (411 g/day; P = 0.16). Milk composition was not affected by diet and CH4 intensity was similar for both diets (22 g/kg fat- and protein-corrected milk; P = 0.31). Methane yield [g/kg predicted dry matter intake (DMI)] averaged 22.6 and 24.9 for cows grazing RyeWC and Diverse pastures, respectively (P = 0.006). In conclusion, although the CH4 yield was greater when Diverse pasture was grazed, relative to RyeWC, there were no differences in emissions intensity or total CH4 emissions. There is a growing interest in diverse pastures containing grasses, legumes and herbs, especially those with a greater tolerance for dry conditions and those that decrease nitrogen excretion from dairy cows. However, the effect of grazing these diverse pastures on the main agricultural greenhouse gas, enteric methane, is not known. Milk solids production was greater in cows grazing diverse pasture than those grazing ryegrass-based pasture, whereas methane production was similar. [ABSTRACT FROM AUTHOR]

Recognition is increasingly given to the need of improving agricultural production and efficiency to meet growing global food demand, while minimising environmental impacts. Livestock forms an important component of global food production and is a significant contributor to anthropogenic greenhouse-gas (GHG) emissions. As such, livestock production systems (LPS) are coming under increasing pressure to lower their emissions. In developed countries, LPS have been gradually reducing their emissions per unit of product (emissions intensity; EI) over time through improvements in production efficiency. However, the global challenge of reducing net emissions (NE) from livestock requires that the rate of decline in EI surpasses the productivity increases required to satisfy global food demand. Mechanistic and dynamic whole farm-system models can be used to estimate farm-gate GHG emissions and to quantify the likely changes in farm NE, EI, farm productivity and farm profitability as a result of applying various mitigation strategies. Such models are also used to understand the complex interactions at the farm-system level and to account for how component mitigation strategies perform within the complexity of these interactions, which is often overlooked when GHG mitigation research is performed only at the component level. The results of such analyses can be used in extension activities and to encourage adoption, increase awareness and in assisting policy makers. The present paper reviews how whole farm-system modelling has been used to assess GHG mitigation strategies, and the importance of understanding metrics and allocation approaches when assessing GHG emissions from LPS. [ABSTRACT FROM AUTHOR]

Here we examine the concordance among emissions, production and gross margins of extensive beef farming systems by modelling a range of scenarios for herd management, animal genotype and pasture nutritive quality. We based our simulations on a case-study farm in central Queensland, Australia, and studied the influence of interventions designed for emissions mitigation, increasing productivity, or increasing gross margin. Interventions included replacing urea supplementation with nitrate, finishing cattle on the perennial forage leucaena (L), herd structure optimisation (HO), higher female fecundity (HF), and a leucaena finishing enterprise that had net farm emissions equal to the baseline (leucaena equal emissions; LEE). The HO intervention reduced the ratio of breeding cows relative to steers and unmated heifers, and lowered the ratio of costs to net cattle sales. Gross margin of the baseline, nitrate, L, LEE, HO and HF scenarios were AU$146 000, AU$91 000, AU$153 000, AU$170 000, AU$204 000 and AU$216 000, respectively. Enterprises with early joining of maiden heifers as well as HO and HF further increased gross margin (AU$323 000), while systems incorporating all compatible interventions (HO, HF, early joining, LEE) had a gross margin of AU$315 000. We showed that interventions that increase liveweight turnoff while maintaining net farm emissions resulted in higher gross margins than did interventions that maintained liveweight production and reduced net emissions. A key insight of this work was that the relationship between emissions intensity (emissions per unit liveweight production) or liveweight turnoff with gross margin were negative and positive, respectively, but only when combinations of (compatible) interventions were included in the dataset. For example, herd optimisation by reducing the number of breeding cows and increasing the number of sale animals increased gross margin by 40%, but this intervention had little effect on liveweight turnoff and emissions intensity. However, when herd optimisation was combined with other interventions that increased production, gross margins increased and emissions intensity declined. This is a fortuitous outcome, since it implies that imposing more interventions with the potential to profitably enhance liveweight turnoff allows a greater reduction in emissions intensity, but only when each intervention works synergistically with those already in place. [ABSTRACT FROM AUTHOR]

This study was designed to screen a large number of sheep to identify individuals with high and low methane (CH4) production, and to estimate repeatability and heritability of CH4 emissions in sheep, utilising portable accumulation chambers (PAC) designed for in-field use. Mature ewes (n = 710) selected from a research flock with known sires had their CH4 production over 1 h measured in PAC [CH4 (g1h)]. Individuals with High (n = 103) or Low (n = 104) CH4 (g1h), adjusted for liveweight (LW), were selected and re-measured on three occasions 1-4 months later, at another site with more abundant and better quality pasture. Mean of the selected (207) ewes CH4 (g1h) emissions were ~50% higher than at the first measurement site (0.66 g vs 0.42 g).LWwas a significant correlate of CH4 production (r = 0.47). Correlations between CH4 (g1h) for the three PAC measurements at Site 2, before adjusting for LW ranged from 0.44 to 0.55. After adjusting for the effect of LW, repeatability was 0.33 at the first and 0.43 at the second site. The correlation between estimates of an animal's emissions at the first and second sites, adjusted for LW, was 0.24. Initial CH4 production of the selected High group was 32% greater than the Low group (P < 0.0001). On re-measurement there was still a significant difference (9-15%, P < 0.006) between Low and High groups. The initial estimate of heritability of CH4 (g1h), based on variation between the ewes' sires (0.13), was not maintained across the two sites. This may be due to genotype. environment interactions. We postulate that aspects of rumen physiology, which modulate CH4 production, could be expressed differently in different nutritional environments. Our results indicate that field use of PAC to screen sheep populations for CH4 production is both robust and repeatable. However, further investigations are required into the relationship between CH4 output of individual animals in PAC compared with the more controlled conditions in respiration chambers. [ABSTRACT FROM AUTHOR]

Enteric methane (CH4]) and faecal and urinary nitrogen (N) are two major pollutants due to ruminants. However, relations between these two components have been seldom studied, and the specific relationships for forage diets are not known. A meta-analysis was conducted using a large database of published data for ruminants fed forages, in which CH4 production, digestibility and urinary N (UN) output were all available. A total of 148 treatments (55 from cattle and 93 from small ruminants) from 29 publications and 56 experiments were used. Globally, there was a positive relationship between CH4 and UN production when expressed either per kg of liveweight or per kg of dry matter (DMI) intake. These relationships were maintained when a subset of 38 experiments that focussed on the influence of variation of DMI were considered. Otherwise, when a subset of 17 experiments that focussed on forage crude protein content were considered, the two equations relating CH4 and UN remained significant but the slopes were much smaller. In conclusion, the positive relationship between CH4 and UN can be mainly explained by the indirect positive influences of DMI or of diet organic matter digestibility on these two parameters. It is important to know if there is any relationship between productions of methane and urinary nitrogen in ruminants. A statistical work was performed on a database to elucidate this issue. For diets including only forages, dietary factors such as dry matter intake level and the organic matter digestibility induce a positive relationship between the productions of these two potential pollutants. [ABSTRACT FROM AUTHOR]

Ruminants contribute to human food supply and also anthropogenic greenhouse gas (GHG) emissions. An understanding of production systems and information on animal populations has enabled global inventories of ruminant GHG emissions (methane and nitrous oxide), and dietary strategies are being developed to reduce GHG emissions from ruminants. Mitigation strategies need to consider the management/feeding systems used to ensure that these strategies will be readily accepted and adopted by farmers. Housed systems allow diets to be formulated in ways that may reduce GHG production, but the challenge is much greater for systems where animals graze outdoors for long periods. A methane mitigation option in the form of fresh forage would be desirable in livestock production systems with high reliance on grazing. A brief summary of New Zealand research, carried out on fresh grasses, legumes, herbs and crops, suggest that we have an incomplete understanding of the feed characteristics that define a 'high' or a 'low' methane feed. The variation in methane emissions measured between feeds, individual animals and experiment is large, even in controlled conditions, and the dynamic nature of sward-animal interactions will only exacerbate this variation, creating challenges beyond the identification of mitigants. Furthermore, implementation of knowledge gained from controlled studies requires validation under grazing systems to identify any trade-offs between methane reduction and animal productivity or emission of other pollutants. Therefore, investment and research should be targeted at mitigation options that can and will be adopted on-farm, and the characteristics of temperate grasslands farming suggest that these options may differ from those for intensive (high input/output) or extensive (low input/output) systems. Dietary manipulation is a key approach to reduce methane emissions from ruminant livestock, but its application in grazing systems is poised with challenges. We reviewed findings from research in New Zealand aimed at characterising 'low methane' feeds for grazing ruminants. Although some progress is evidenced from animal experiments, on-farm productivity and profitability are yet to be integrated in the meaningful evaluation of mitigation approaches. [ABSTRACT FROM AUTHOR]

In response to climate change, research is being undertaken to understand the on-farm greenhouse gas emissions and water use for agricultural systems and investigate options farmers may have for mitigating or offsetting emissions. In the present study, a life cycle assessment framework is used to determine on-farm GHG emissions and water use, and the overall 'cradle-to-farm gate' GHG emissions and water use attributed to beef production. The total on-farm emissions for the two properties were 2984 t CO2-e/year (or 1.93 t CO2-e/ livestock unit) for the 634-cow enterprise turning off weaner cattle at Gympie and 5725 t CO2-e/year (or 1.70 t CO2-e/livestock unit) for the 720-cow enterprise turning off finished steers in the Arcadia Valley. The on-farm emissions are largely attributable to enteric methane emissions from the beef herd. The overall 'cradle-to-farm gate' GHG emissions associated with enterprise products were 3145 t CO2-e/year at Gympie and 7253 t CO2-e/ year in the Arcadia Valley, with the additional emissions coming from off-farm inputs (fuel for farm vehicles and earth-moving equipment, electricity, supplementary feed, agricultural chemicals, farm services) and additionally, for the Arcadia Valley enterprise, from purchased store steers. The carbon footprint of beef products at the farm gate ranged from 17.5 to 22.9 kg CO2-e/kg liveweight at Gympie, where wearers are the primary product, and from 11.6 to 15.5 kg CO2-e/kg liveweight in the Arcadia Valley, where finished steers are the primary product. Green water use ranged from 7400 to 12 700 L/kg liveweight depending on class of livestock, with on-farm blue water use of 51-96 L/kg liveweight and off-farm blue water use of 0.1-59 L/kg liveweight. The ability to offset on-farm GHG emissions through reforestation varied between the two locations, with predicted biosequestration rates of 19.3-34.7 t CO2-e/ ha per year at Gympie (rainfall 1200 mm/year) from eucalypt plantation and 1.5-9.8 t CO2-e/ha per year in the Arcadia Valley (rainfall 600 mm/year) through reforestation from a combination of brigalow regrowth, leucaena and environmental eucalypt plantings. The area that would need to be reforested to offset on-farm emissions (over a 30-year time horizon) would be 86-155 ha at Gympie (7-13% of the holding) and 629-4108 ha in the Arcadia Valley (9-60%). If carbon sequestration could be achieved at the higher end of the rates nominated, a significant proportion of on-farm emissions could be offset by sequestration in timber, with minimal impact on beef production. However, at the lower end of the forest sequestration range, the required level of land-use change would reduce the carrying capacity, and hence beef production, especially at the Arcadia Valley site. [ABSTRACT FROM AUTHOR]