9. Greenpackage
The Greenpackage provides specific project support for activity that will advance progress in the achievement of the goals and objectives established in Environment 2010: A Statement of the Government's Strategy for the Environment.
The three projects reported in this section were funded from the Non CO2 Greenhouse Gases strand of the Greenpackage and managed by MAF in collaboration with the Ministry for the Environment.
9.1 GPK 010
Programme Title: |
Methane emission from sheep and dairy cows grazing kikuyu grass. |
| Programme Leader: | Dr Marc Ulyatt and Dr Keith Lassey |
| Institution: | AgResearch, Grasslands Research Centre and NIWA |
Summary
This programme aimed to obtain accurate methane emission measurements from grazing ruminants and follows on from work undertaken in February 1997. Measurement of methane emission from sheep and dairy cows grazing kikuyu grass was repeated in March 1999 using the SF6 tracer technique. Theoretically methane emission from C4 tropical grasses should be high, but these experiments showed values that were extremely low, suggesting inhibition of methane production in the conditions applying.
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Background
This project complements earlier work completed within PGSF Programmes and with Greenpackage funding. In February 1997, a campaign was undertaken using sheep and dairy cows grazed on kikuyu grass-dominant pastures, to investigate the hypothesis that such C4 grasses, because of their high cell wall carbohydrate content, should result in high methane emissions. Emissions were high for the cows fed kikuyu grass (422g/d) compared to cows at the same stage of lactation in the Manawatu fed a ryegrass/white clover pasture (204g/d). However, the sheep fed kikuyu grass emitted 18.5 g/d, which was similar to sheep fed ryegrass/white clover.
Due to technical difficulties encountered in this work it is important to clarify the situation with respect to kikuyu grass because of the southwards migration of C4 grasses under the influence of global warming.
Approach & Outcomes
The experiments were conducted at Old Oak Farm, Waimate North under normal farming practice. The kikuyu grass-dominant pastures were topdressed with urea at 60 kg/ha/month for the four months prior to the experiment to encourage kikuyu grass dominance and suppress any white clover. Measurements were made for five consecutive days from 10 lactating Friesian cows (454-580 kg) and 12 Romney cross wether sheep (29-40 kg). All animals were given one break of pasture each day and the pasture allowance ensured that feed was never limiting. The animals were dosed at least one week prior to the experiment with SF6 permeation tubes to provide the tracer gas used in the estimation of methane emission with the technique of Johnson et al. (1994).
Methane emission (g/d) |
DM Intake (kg/d) |
DM digestibility (%) |
|
Sheep |
4.4 |
0.71 |
64.1 |
Cows |
177.4 |
13.93 |
63.9 |
Methane emission is expressed as g/kg DM intake, with the 1997 results given in parentheses, was 6.2 (21.4) for sheep and 12.7 (22.1) for dairy cows. Clearly methane emission per kg DM in 1999 was much lower than in 1997. The reason for this difference is not known at present.
Reference: Johnson, K. A., Huyler, M. T., Westberg, H. H., Lamb, B. R., and Zimmerman, P. (1994a). Measurement of methane emissions from ruminant livestock using a SF6 tracer technique. Environmental Science and Technology 28, 359-62.
9.2 GPK 010
Programme Title: |
Factors affecting methane formation in the gut of sheep |
| Programme Leader: | Dr Keith Joblin |
| Institution: | AgResearch, Grasslands Research Centre |
Summary
This programme aimed to provide a method that can readily identify and monitor methanogen populations in the rumens of New Zealand livestock. A sensitive and specific DNA probe technique was developed and tested successfully against DNA extracted from known cultures of microbes. In a single test against DNA extracted from rumen contents from a ‘high’ and from a ‘low’ methane sheep, the PCR-MPN method indicated that there were differences in the rumen populations of the two animals, but there was insufficient time to confirm this. A significant proportion (10%) of ruminant methane emissions arises from the hindgut rather than the rumen. The results indicate that the most probable cause of this are Methanobrevibacter spp which pass through the abomasum to inoculate the hindgut.
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Background
The goal of this project was to develop and establish DNA probe technology for monitoring methanogenic populations in rumen digesta, and to enumerate and identify predominant methanogens in sheep abomasal fluid.
In order to develop strategies for lowering ruminant methane emissions, the relationships between animal emissions and activities and population levels of the differing methane-forming microbes (methanogens) in the rumen need to be understood. To do this, quick accurate methods for measuring methanogens are needed. Because procedures used previously do not detect non-culturable methanogens, the project aimed to develop and test molecular probe technologies for measuring specific methanogenic populations in rumen digesta. In a second part of the study, because ruminant methane produced in the hindgut might be more amenable to mitigation strategies than methane produced in the rumen, the aim was to identify the predominant methanogens moving to the hindgut of sheep.
Approach & Outcomes
The application of the polymerase chain reaction (PCR), in combination with DNA primers specific for microbial taxons, is a sensitive method for monitoring specific populations in microbial ecosystems. Thus, it was decided to develop and establish MPN-PCR methods specific for Archaea, and for specific families of ruminal methanogens. Putative primers were designed from sequences in the literature, international databases or from our methanogen 16S rRNA gene database. To obtain useful information from DNA probe data, a method for reliably extracting representative DNA from samples was required. Several extraction methods were tested and the method producing the highest quality DNA used in further experiments.
Abomasal contents were collected anaerobically from sheep fitted with abomasal cannulae and enumerated by dilution and culturing in appropriate anaerobic media. A most probable number (MPN) method was used to obtain more precise data. The predominant methanogens were cultured on H2/CO2 using specific media and colonies isolated by multiple cycles of selection. Two pure methanogenic isolates were selected for study.
Most of the work involved testing various combinations of forward and backward primers against DNA extracted from NZ isolates of Methanosarcina barkeri and Methanobacterium formicicum and from non-methanogenic rumen bacteria. Primer combinations were successfully developed for the appropriate targets and optimal PCR conditions were established for amplification of the three target DNAs. At the end of the project, there was sufficient time to carry out a single test on DNA extracted from rumen contents from a high-methane sheep and a low-methane sheep. The PCR-MPN analyses suggested that low-methane sheep contained 10-fold more Archaea than high-methane sheep. This preliminary experiment also suggested that the low-methane sheep had more non-methanogenic Archaea and less Methanobacteriales than the high-methane sheep. It should be emphasised that this interpretation is based on only a single experiment. Further work is needed to obtain confirmatory data and to extend this study.
In the case of methanogens passing through the abomasum, in one sheep the viable abomasal methanogen population density was found to be 3 x 107 cells ml-1 and in the other 1.3x108 cells ml-1. These results were surprising because rumen microbes are presumed to breakdown under the very acidic conditions in the abomasum. Following purification, two methanogen isolates resistant to lysis in the abomasum were identified from their phenotypic characters as Methanobrevibacter spp.
Publications
Results on abomasal methanogens are being prepared for publication.
9.3 GPK 020
Programme Title: |
Nitrous oxide emissions |
| Programme Leader: | Keith Cameron |
| Institution: | Eco-Link (Completed by Lincoln University) |
Summary
This programme aimed to identify gaps in knowledge in respect of agricultural nitrous oxide emissions, and develop a strategic approach to further research. A literature review was undertaken and a workshop of expert participants was held at Lincoln University. This research successfully identified further work required to categorise agricultural nitrous oxide emissions, by identifying and prioritising information and research needs that are crucial in allowing New Zealand to meet existing commitments on climate change, and to prepare it to meet the forthcoming requirements for the Kyoto Protocol.
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Background
The Kyoto Protocol to the United Nations Framework Convention on Climate Change, subject to its ratification and coming into force, establishes legally binding commitments for developed countries to reduce greenhouse gas emissions. The goal of this project was to scope directions for further work categorising agricultural nitrous oxide emissions by identifying and prioritising information and research needs that are crucial in allowing New Zealand to meet existing commitments on climate change and to prepare it to meet the forthcoming requirements for the Kyoto Protocol.
Approach & Outcomes
A contextual briefing was held to ensure that the nature of New Zealand’s international commitments, recent policy developments and science directions were fully reflected in the project. A post-1995 review of the literature and related Framework Convention on Climate Change (FCCC) activities was prepared and circulated to expert participants of a one day workshop held at Lincoln University. Participants at the workshop identified available information on nitrous oxide emissions in New Zealand, identified the gaps in the necessary research and information, prioritised the research and information needed, and identified a strategy for gathering and updating the necessary information, including processes for liaison/collaboration/ cooperation and feedback.
The literature review and workshop identified the following top priorities for research and information needs:
- Excreta deposited during grazing: refine the current New Zealand emission factors for direct emissions from excreta deposited during grazing for different situations/areas.
- Process-based models: develop robust process-based models, in combination with large spatial and temporal data sets, of the major drivers of N20 production (e.g. land cover/land management, climate, soil type, soil aeration/moisture status) to help refine and validate, our national N20 emission estimates
- Indirect sources of N20: refine the current New Zealand emission factors for indirect sources of N20 namely: nitrate leaching, atmospheric deposition.
A national science working group was established to develop the research approach and methodology required to obtain the necessary knowledge and information to allow New Zealand to meet existing commitments on climate change, and to prepare it to meet the forthcoming requirements for the Kyoto Protocol.
Publications
The literature review will be submitted to an appropriate journal for publication.
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