The NZAGRC methane programme is jointly planned and funded in partnership with the PGgRc and aligns with existing MPI programmes funded through SLMACC and New Zealand funding in support of the Global Research Alliance on agricultural greenhouse gases. It aims to reduce emissions by directly targeting the methane producing methanogens through the discovery of small molecule inhibitors and vaccines and indirectly through feeding and changes in animal phenotype.
- Breeding: Research to understand the genetics of host control of ruminant methane emissions, which aims to develop genetic and genomic selection technologies to reduce methane yield and intensity in sheep. The current stage of the programme involves the development and dissemination of practical tools for selection for lowered emissions. A major part of maximising impact and uptake is to explore relative economic value from increased production and potential increased feed utilisation associated with lowered methane
- Vaccine (jointly supported by PGgRc): A prototype vaccine (which after further development is aimed at producing a vaccine targeted at reducing methane emissions in cattle and sheep by 20%) is being formulated with the help of a commercial partner
- Inhibitors (previously jointly funded but now fully funded by PGgRc): Research to develop cost-effective inhibitors that reduce methane emissions by at least 20% in sheep and cattle—without reducing productivity—is now being developed, with a view to bring the technology to market
- Modelling: A tool to help scientists in the NZAGRC/PGgRc programme to develop hypotheses and predict responses in methane formation is in its final stages
Current progress and research stories
The current objectives within the NZAGRC methane programme have made significant progress this year, with the sheep breeding programme getting closer to delivering breeding values to the national flock.
Methane emissions changed nonlinearly with graded substitution of alfalfa silage with corn silage and corn grain in the diet of sheep and relation with rumen fermentation characteristics in vivo and in vitro
Jonker, A., K. Lowe, S. Kittelmann, P. H. Janssen, S. Ledgard, and D. Pacheco. 2016. Methane emissions changed nonlinearly with graded substitution of alfalfa silage with corn silage and corn grain in the diet of sheep and relation with rumen fermentation characteristics in vivo and in vitro12. J. Anim. Sci. 94:3464-3475. doi:10.2527/jas.2015-9912
Feeding grain and corn silage have been proposed as practices to reduce enteric methane (CH4) emissions per unit of intake from ruminants, but the inclusion level required in the diet is normally not specified. The objectives of the current study were to determine the CH4emission factor (g/kg DMI) of sheep fed alfalfa silage substituted with increasing levels of corn silage or corn grain at a fixed DMI level (2% of BW) and determine its relationship with rumen fermentation characteristics and microbial community composition and with in vitro fermentation characteristics of the same diets incubated using a standard laboratory method. Romney ewe hoggets (approximately 14 mo old; n = 64) were randomly allocated to 8 dietary treatments, which included chaffed alfalfa silage alone or substituted with either 25, 50, 75 or 100% corn silage or 25, 50 or 65% rolled corn grain on a DM basis. After acclimatization to the diet, DMI and CH4 emissions were measured from individual sheep for 2 consecutive days in open-circuit respiration chambers and a rumen sample was collected at 3 h after feeding. The same diets were also incubated in an automated in vitro gas production system for 48 h using rumen liquid of fistulated nonlactating dairy cows grazing pasture. Increasing the substitution of alfalfa silage with corn silage or corn grain in the diet of sheep resulted in a quadratic response (P < 0.01) in CH4 emissions per unit of DMI (CH4/DMI) with either supplement. For both supplements, CH4/DMI increased in mixtures of up to 50% supplement inclusion and then decreased with greater supplement inclusion, especially with corn grain inclusion, but the level did not fall below that for 100% alfalfa silage. The ratio of acetate + butyrate to propionate + valerate and the propionate proportion alone in rumen liquid were the strongest single predictors for CH4/DMI in the overall data set and explained 37.1 and 32.5%, respectively, of the variation in CH4/DMI. Methanogens of Methanobrevibacter ruminantium(21.1% of total methanogens; r = 0.247) and Methanosphaera spp. (10.7% of total methanogens; r = −0.411) clades had weak to moderate correlations with in vivo CH4/DMI. There was a weak quadratic relationship (r2 < 0.35) between in vivo CH4/DMI and the in vitro parameters of gas and CH4 production and total VFA, whereas there was a moderate relationship (r2 = −0.50) between in vivo CH4/estimated rumen degradable carbohydrates and in vitro CH4/DM. In conclusion, CH4/DMI changed in a nonlinear fashion with increasing supplement inclusion in the alfalfa forage diet when fed at 2% of BW to sheep; however, implications on predicting its influence on greenhouse gas emissions per unit of animal product, for whole farm emissions in life cycle analysis or total national emissions in the national inventories, should be determined.
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