The amount of beef produced per animal in Canada has significantly increased over the past 30 years. To produce the same amount of liveweight for slaughter in 2011 as in 1981, 29% fewer cattle in the breeding herd and 24% less land were required. Greenhouse gas emissions per kilogram of liveweight declined by 14% during this period, owing to improved production efficiencies such as higher reproductive efficiency, bodyweight gains and increased crop yields.

Methane production by cattle contributes to global warming, and estimating daily methane production (DMP) in natural environments is a prerequisite for mitigation strategies. The GreenFeed system is well suited to indoor and pastoral systems, and estimates DMP from cattle using multiple short-term measurements. We evaluated GreenFeed for implementation and accuracy of DMP, and found values to be comparable with other measurement techniques, but required more animals and longer periods to provide robust estimates.

Livestock production is the main source of greenhouse gases in agriculture in Australia. A novel airborne approach using modern gas analysers for methane and ammonia was tested at a feedlot. The flights were able to define the 3D-boundaries of, and the concentration levels within, the emission plume. Our results suggest that this technique is able to quantify emissions from sources within a feedlot, as well as determining emissions from large-scale open grazing farms.

There are few methods available to accurately and repeatedly assess methane production from large numbers of individual grazing animals. An intra-rumen gas-sensing system incorporating commercially available gas sensors was developed to measure rumen gas concentrations in real-time. Although the devices can measure for several weeks in the rumen, the accuracy declines due to the harsh rumen environment. Therefore, future research needs to focus on building a new generation sensor or finding other ways of protecting the currently available commercial sensors.

Beef cattle are responsible for a substantial component of methane emissions from Agriculture, and the beef industry is keen to address this issue. This study examines whether methane measurements on beef cattle are repeatable over time. Measurements of methane conducted within a short time frame are highly repeatable, while measurements taken over longer time-frames are substantially less repeatable. These results indicate that multiple measures may be required to accurately record methane traits throughout an animal’s life.

The GreenFeed system has been developed to provide individual measures of enteric methane emission and can be used in breeding programs for selecting low-emitting cattle. Based on spot-measures, the method requires averaging several day measurements for reaching a high enough repeatability. This work showed that averaging ~100 spot-measures recorded in a 4-week test period provided high repeatability (>0.77) for methane emission of beef heifers.

Nitrate is an effective feeding strategy to mitigate methane emissions in ruminants. By studying the dose-response effect of this compound on metabolic hydrogen distribution among rumen fermentation end products, this in vitro study showed that nitrate acts as an electron acceptor, but its mechanisms of action must also involve a direct toxic effect on methanogens. This result completes previous in vivo trials by detailing the mechanisms of action of nitrate on rumen fermentation.

Methane is a potent greenhouse gas produced by cattle and sheep during the process of digestion of plant material. This experiment showed that measurement of rate of carbon dioxide exhaled or of weight gain can be used as proxies for feed intake to adjust methane measurements when feed consumed by individual animals cannot be measured. This provides a new method of identifying identify those animals that emit higher or lower levels of methane than their intake in situations where feed intake cannot easily be measured in greenhouse-gas measurement experiments with beef cattle.

Information on the precision of different methods used to measure enteric methane emissions in cattle is important for the design of experiments. This work provides results on repeatability of measurements and on cows’ number required when determining methane emissions using the SF₆ tracer technique and GreenFeed system. A repeatability of 0.70 was observed after 3 and 17 days of measurement with SF₆ and GreenFeed, respectively, whereas the number of cows necessary to observe methane emission differences was the same for both methods.

The Ankom^RF system for conducting in vitro studies on rumen fermentation employs a reaction vessel and a valve that vents excess gas when a pressure transducer detects the build-up of gas to a predetermined threshold. The current research presents mathematical formulae and methodologies that take account of the venting and enable accurate estimation of methane production in this system. This innovation will facilitate methane-production studies in many laboratories around the world.

Dairy cows produce methane during digestion, and lowering emissions could lessen global warming. A method for estimating methane emissions from grazing cows, requiring individuals to eat (and breathe) in a semi-enclosed feeder equipped with sensors, was evaluated on four occasions during a lactation in two farmlets in New Zealand. This ‘GreenFeed’ system provided defensible data from 50% to 70% of cows in small herds, and it could be used to monitor farming practices designed to reduce cow methane emissions.

Methane production by cattle is a major contributor to anthropogenic greenhouse gases. We produced a feed supplement from readily available, inexpensive feedstuffs in southern Australia, and demonstrated that it was effective in reducing methane output from cattle. Incorporation of by-products with methane-reducing potential into commercial feeds is a cost-effective means of reducing methane output.

The red macroalgae Asparagopsis taxiformis has demonstrated a potent methane abatement effect in vitro. At a low inclusion level of 2% of substrate organic matter methane emissions were eliminated with minimal effect on substrate digestibility while improving the ratio of beneficial energy molecules for potential use in animal productivity.

Ruminant production is limited by low-quality diets and by the loss of energy intake to methane production, which contribute to greenhouse gas emissions. Strategies to reduce methane production from ruminants may affect animal productivity; removal of rumen protozoa in combination with nitrate supplementation additively increased productivity and decreased methane production. The results of the present study added new knowledge of combining two methane mitigation strategies to reduce greenhouse effects and increase productivity of ruminant animals consuming low-protein diets.

Forage brassica and chicory can be used in summer as feeds for lactating dairy cows but neither showed any methane mitigating effect. The concentrations of specific fatty acids in milk were generally not related to methane emission or yield.

The interaction between dietary crude protein and forage content and their impact on enteric methane emissions and nitrogen excretion are not experimentally quantified in dairy cows. Cows receiving reduced crude protein diets had low manure nitrogen outputs and improved milk true protein production efficiencies, regardless of dietary forage content. Cows receiving reduced forage content diets had lower methane emissions as well as emission per unit of milk yield. This study provided some insights to understand the relationship between nitrogen excretion and methane emissions.

Ruminant-based products are strongly criticised for their greenhouse gas emissions. The large individual variation of estimated emissions from bulls during their fattening is related to their performances and management indicating that mitigation option exists at this stage of their life. However, to ensure an effective greenhouse gas emission mitigation option the whole life of the bull has to be considered.

An aerobic treatment technology using carbon fibre carriers was capable of mitigating emission of nitrous oxide. To mitigate emission of nitrous oxide during swine wastewater treatment, we demonstrated a reduction in greenhouse gases emissions at a practical level. The aerobic treatment technology reduced nitrous oxide emission by more than 60%, compared with an activated sludge treatment. Smooth conversion from NH₄⁺ to N gas enabled treatment without the accumulation of NO₃^– and NO₂^–, thus avoiding excessive nitrous oxide emission.

An increase in nitrous oxide (N₂O) emissions is possible where urine patches in grazed pastures coincide with dung patches and farm dairy effluent (FDE) applications. To test this, a field experiment was conducted to quantify N₂O emission factors for urine (EF, % of applied urine-N emitted as N₂O). Our results suggest that dung addition or FDE application can increase urine EF, which should be considered when N₂O emissions from grazed pastures are calculated.

Acidification of manure is an effective measure for greenhouse gases (e.g. carbon dioxide, methane, nitrous oxide) and ammonia emission mitigation. In this study we tested a new technique based on the addition of a powdery sulfur-based product (80% elemental sulfur concentration) to the manure. This technique was a reliable and effective way to acidify the separated solid fraction of raw and co-digested pig slurry, and reduced greenhouse gases (up to 78%) and ammonia (up to 65%) emissions from stored manure.

Nitrous oxide (N₂O) is a greenhouse gas with high global warming potential. Animal urine deposited onto pastoral soils during grazing has been identified as an important source of N₂O emissions and the nitrification inhibitor dicyandiamide (DCD) can be used as a mitigation technology to reduce N₂O emissions. This study investigated an innovative method of DCD delivery to animal urine and determined an optimum DCD application rate for achieving maximum N₂O reduction.

The manure deposited in dairy barnyards can be a large source of nutrient loss and gas emission. Fluxes of carbon dioxide, methane, ammonia and nitrous oxide were measured from barnyards in Wisconsin, USA, over 4 years. Bark surfaces generally had the highest gas emissions, followed by sand and soil. Tradeoffs between gas emissions, manure nutrient runoff and leaching, cow comfort and health need to be assessed more fully before recommending beneficial practices for barnyard construction and management.

Nitrous oxide (N₂O) is the main greenhouse gas (GHG) produced by soil fertiliser. Previously, we introduced a novel clay-based technology to abate these emissions. Here, we test the technology at the glasshouse scale, with a model plant included. The technology achieved >50% decrease N₂O emissions. Our technology could offer a simple way forward to decrease emissions from a significant agricultural GHG source.

We assessed the impact of management and animal interventions on the relationships between gross margin, greenhouse gas mitigation and emissions intensity of a rangeland beef farm. Profitable strategies included finishing cattle on perennial legumes, optimising steer and heifer sale times, and adopting crossbreds with high female fertility. There was little relationship between gross margin and emissions intensity when individual interventions were applied to the base farm, but a significant, negative relationship emerged when several interventions were applied.

For approved carbon offset methods to be used by producers, returns need to outweigh costs. Monte Carlo simulations of beef production systems on coastal speargrass in central Queensland were run with probability functions used for: (1) urea, nitrate and cottonseed meal prices; (2) greenhouse gas mitigation; (3) livestock sale prices; and (4) carbon prices. The required carbon prices for a 2% return on capital were an order of magnitude higher than current carbon prices for the three forms of nitrate without including the costs of participating in carbon offset projects. The economics of mitigation options are often not evaluated.

Many potential management techniques that livestock farmers could use to reduce livestock greenhouse gas emissions are rarely taken up by the industry, despite decades of research into their effectiveness. Research on sheep and cattle emissions rarely addresses actual end-use and farmer implementation, so this study modelled farmer adoption of different emission reduction techniques, and found wide variation in their maximum adoption levels and time to reach it. We found that feeding lipids and increasing ewe reproductive efficiency had the lowest and highest adoption rates, respectively.

It is important to clarify whether rhubarb can reduce methane production in vivo. A decrease in methane partial concentration was demonstrated by the ruminal gas samples of rhubarb-treated steers. In addition, 16S rRNA sequencing of rhubarb-treated rumen liquor showed increases in Prevotella. These findings indicate that rhubarb effectively decreases methane gas emission with a concomitant increase in propionate in vivo.

Data on the effect of grassland management on grass characteristics in combination with enteric methane (CH₄) emission in lactating cows is sparse, as well as studies evaluating this relationship. We evaluated an extant mechanistic model of enteric fermentation against observations on the effect of grassland management on CH₄ emission, and found that a systematic difference in observed versus predicted values is largely caused by erroneous prediction of VFA profile. Model representations of feed digestion and VFA profile are key to predict enteric CH₄ accurately, and particularly the latter requires further evaluation.

Ruminant livestock production generates higher levels of greenhouse gas emissions compared with other types of farming. Yet farms often contain substantial areas of trees that sequester carbon while providing additional co-benefits such as shelter, biodiversity, along with reduced erosion and salinity. This study demonstrated that sheep farms can be carbon neutral by sequestering carbon in trees and soils, which offset the emissions from sheep, fuel and electricity.

Climate change is the most serious environmental challenge, which is threatening the well-being of future generations. After energy, industry and forestry sectors, livestock are the significant contributor of climate change, representing 14.5% of the global greenhouse gas emissions. The carbon footprint of cow and buffalo milk in Anand district was 1.9 and 2.5 kg CO₂-eq/kg fat- and protein-corrected milk (FPCM), respectively and was far below the global estimates (i.e. 5.5 and 3.2 kg CO₂-eq/kg FPCM for cow and buffalo, respectively) for southern Asia.

The supplementation of tropical plants into the diets of ruminants is thought to be an economically feasible method for decreasing CH₄ emissions, compared with other forages. Tithonia diversifolia is a tropical shrub and was supplemented at three different concentrations (6.9%, 15.2% and 29.2%, DM basis) to evaluate its in vitro influence on rumen fermentation characteristics and CH₄ production. There was no effect of Tithonia diversifolia on CH₄ production when supplemented at 6.9% (DM basis), suggesting that at low replacement rates, this plant could potentially be used as an alternative feed.

The scale of global cotton and canola production creates a challenge and opportunity for producers to utilise their by-products and abate greenhouse gas emissions (GHG). We showed that the emission abatement of using cotton and canola seed oil for biodiesel was greater than that from feeding the oil to cattle. Results of the present study provide an indication of what are the best options for dealing with cotton and canola by-products in terms of the net GHG effects.

This manuscript summarises New Zealand studies on the effect of feeding forage brassicas to ruminants on enteric methane emissions. From a series of experiments with sheep and cattle fed winter and summer varieties of brassica forage crops, we found that feeding several species, especially winter forage rape, can result in a lower methane yield than ryegrass pasture. This is an important finding as part of assessing these crops as methane mitigation options for pastoral systems.

In the face of climate variability, it is imperative to implement sustainable interventions to reduce the carbon footprint of the ruminant industry. This study assessed the clinical feasibility of tea seed (Camellia sinensis L.) saponin (TSS) associated with intake, liveweight, rumen fermentation and blood biochemistry responses. Supplementation of 151 ± 2.77 mg of TSS/kg LW is toxic to Brahman cattle.

Reports on the effect of high hydrogen pressure on rumen metabolism of dairy cows in vivo are scarce. When hydrogen was infused into the rumen of dairy cows for 5.75 h at 48 L/h, only 2.7% was retained in the rumen, leading to increased methane production from 120 L/5 h to 130 L/5 h, which was probably due to low solubility of hydrogen in rumen liquid. It remains a challenge to modify the rumen hydrogen pressure in vivo.

Livestock contributes ~37% of the anthropogenic production of methane emission, mostly by large ruminants (cattle and buffalo). The present study was designed to evaluate the effects of plants as methane inhibitors on rumen metabolites and methanogen diversity of buffaloes. The ammonia-N concentration and ciliate protozoa population were reduced significantly in the supplemented groups. Methanogen diversity showed the possibility of Methanobrevibacter as the major methanogen. Sequence study of a large number of clones will help in understanding the true picture of rumen methanogen diversity and methane mitigation strategies can be planned accordingly.

This study provided a gate-to-gate Life Cycle Assessment that modelled the greenhouse gas emissions of three herds bred and grown by an integrated beef cattle enterprise across northern Australia. The results show reductions of greenhouse gas emissions when cattle are shifted to more intensive forms of herd management, such as lot feeding. However, emission reductions are dependent on the days spent grazing and associated liveweight gains on growing and backgrounding properties.

Worldwide, there is increasing pressure to reduce greenhouse gas emissions from livestock to avoid dangerous changes to our climate. The present study aimed to estimate greenhouse gases per unit of milk, or carbon footprint, from grass-based dairy farms and identify reduction strategies. Our results indicated that the carbon footprint of milk could be reduced by increasing herd genetic merit, extending the length of the grazing season and optimising N fertiliser use. Grass-based farmers can simultaneously improve these farm attributes and, thereby, significantly reduce carbon footprint.

Microbial digestion in the fore stomachs allows ruminant animals to utilise cell-wall carbohydrates, but at the expense of producing methane that is a strong greenhouse gas. The objective of the present study was to evaluate possible contribution of variation in digesta mean retention time from the rumen to among-animal variation in methane emissions, by using a mechanistic model. Predicted methane emissions increased with increased mean retention time, but negative effects on diet digestibility should be considered before starting to select low emitters.

Greenhouse gas emission intensities (EI) were modelled for Merino ewe, Merino-cross ewe and Merino wether enterprises at 28 sites across eight Australian climate zones. The aim was to determine if EI are reduced by any management changes designed for climate change adaptation and to study how EI varies with climate zone and enterprise specialisation. Overall, animal breeding options reduced EI more than feedbase interventions and EI were highest in Merino wether flocks and in cool temperate regions with high rainfall and lowest in crossbred ewe flocks and in semiarid and arid regions.

Feed production and feeding determines the emissions of greenhouse gases from livestock production systems; and the profitability and overall sustainability of the livestock sector. This article presents promising innovations and practices in feed production and feeding that contribute to the desired triple gain: economic, environmental and social sustainability of livestock production systems in addition to enhancing food security.

The yearly methane emission from cattle is, in most countries, based on the methane conversion factor (Y_m, %) describing the proportion of the gross energy intake lost as methane. The aim was to predict this conversion factor based on Danish experimental and farm data. The international climate panel suggests that 6.5% is used, but the results showed a lower methane conversion factor for Danish dairy cows (5.98–6.13%), which is in accordance with the high production level.

The milk fatty acid (FA) profile has been suggested as a simple indicator to estimate methane production in dairy cattle. We evaluated the relationships between methane production and milk FA profile in dairy cattle fed grass- or grass silage-based diets, and found that quantitative relationships between milk FA profile and methane production in cattle fed grass- or grass silage-based diets markedly differ from those determined for other types of diets published in literature. The implementation of milk FA profile as a simple, easy-to-use indicator of methane production in practice may require diet-specific prediction equations.

Manure hotspots are a significant source of the greenhouse gas nitrous oxide, but spatial heterogeneity is generally not accounted for in models of nitrous oxide emission from soil. An incubation experiment with three manure materials, two soil types, and three soil water potentials was used to analyse patterns of nitrous oxide emission with a conceptual model that includes two compartments, manure hotspots and bulk soil, with different emission potentials. The study highlights the need to account for heterogeneity.

Livestock are significant contributors to greenhouse gas emissions. Although there are numerous equations developed to estimate methane emissions from livestock, most of them are not applicable in commercial dairy because they require inputs not routinely measured in such operations. We have developed equations that use milk yield and composition information to estimate methane production and associated errors. This will help in evaluating mitigating strategies in commercial dairy farms.

Dairy heifers contribute to the dairy industry’s greenhouse gas footprint without producing milk.  In sub-tropical dairy regions the use of high quality supplementary feed to improve live-weight gain and reduce time to first mating has been shown to reduce their life time emissions intensity of milk production.  The Australian dairy industry is identifying ways to reduce its carbon footprint and accelerating the live-weight of dairy replacement heifers, particularly in northern Australia, is viewed as an effective and viable mitigating option.

A better estimate of enteric methane production from sheep is necessary for more accurate preparation of national greenhouse gas inventory. This study aimed to develop models for prediction of enteric methane production from sheep and showed that few models improved the prediction of methane production. These models could precisely estimate enteric methane emissions and assess the costs and benefits of enteric methane mitigation from sheep.

There is growing interest in the potential of soil carbon sequestration as an offset against livestock emissions in grazing systems. A systems modelling study showed full offset of livestock emissions only at a low-rainfall, low-productivity site, where initial soil organic matter was low. Soil carbon may initially offset livestock emissions in the years following a transition from cropping to permanent pasture, but this offset diminishes as soil carbon approaches a new equilibrium.

This study modelled the greenhouse gas emissions (GHG) of beef cattle herds grazing irrigated leucaena paddocks on a property in northern Queensland, Australia. GHG emissions were compared with the emissions of cattle grazing native pasture. The results showed reductions in GHG emission intensities between 53% and 57% when cattle graze leucaena and long-term GHG emission reductions were modelled when factoring in the carbon sequestration of the leucaena paddock.

Supplementing ruminants with dietary nitrate reduces methane emissions, but can expose animals to nitrite toxicity risks. This study investigated if adaptation to dietary nitrate and supplementation of fermentable energy sources reduce accumulation of nitrite in vitro. However, there was no effect of additional energy on nitrite accumulation, and adaptation of rumen fluid donors to dietary nitrate even increased accumulation of nitrite. In vivo verification is needed to assess the role of adapting ruminants to nitrate supplementation on risks of nitrite toxicity.

A requirement for evaluating the environmental footprint of African pastoral systems is to have reliable information on methane emission from forages consumed by ruminants. This work shows a large seasonal variation of methane emission determined in vitro that was partly explained by forage chemical composition. This is a first step of a more accurate determination of methane effectively produced by cattle managed on African pastures.

Ruminants in developing countries are maintained mainly on a low-quality diet that is poorly utilised, resulting in low productivity. The present paper assessed the effects of protein supplementation on improving utilisation of low-quality diet in cattle, with the outcome indicating increased intakes and nitrogen retention; however, dry matter digestibility was unaltered. This may imply that supplementation at submaintenance intake may improve nitrogen utilisation in cattle, but fibre utilisation may not be improved.

The methane emission from ruminant livestock has a greenhouse gas effect. This experiment examined suppressing the effects of peanut, rapeseed, corn and soybean oils to methane production from adult goats. The results showed that soybean oil reduced methane production more effectively than the other oils and could be used as an ingredient in ruminant diets for methane mitigation.

Livestock production from the communal as well as commercial farms under extensive production systems needs to be competitive globally in terms of production cost and environmental foot print associated with the production of meat and milk. The use of selected browse foliage from the Kalahari Desert in South Africa to supplement Eragrostis trichopophora hay in order to improve in vitro ruminal fermentation and associated methane production was studied. Browse foliage with good methane mitigation potential will be identified for subsequent evaluation using in vivo trials.

Management strategies for reducing methane emissions from livestock in forage-based grazing systems may include a selection of plants with the potential to alter methane production in the rumen. While a range of conventional forages have been reported to reduce ruminal methane, there is an array of emerging forages yet to be investigated for their methane mitigation potential. In the current study, we have found that some alterantive forages such as chicory, broccoli and plantain may mitigate production of methane by ruminants.

Ruminant livestock systems in harsh climatic regions are associated with high greenhouse-gas (GHG) emissions and production costs. The use of food by-products from local agro-industry can help to overcome these issues. We analysed the environmental implications of two alternative dietary strategies for dairy goats, including tomato-fruit wastes and olive oil by-products. Results showed animal feeding is the preferable option for GHG mitigation in this case, but the implications of other competing uses for organic by-products (biogas, compost) must be carefully considered.