title: Genetic and environmental variation in methane emissions of sheep at pasture.
abstract: A total of 2,600 methane (CH4) and 1,847 CO2 measurements of sheep housed for 1 h in portable accumulation chambers (PAC) were recorded at 5 sites from the Australian Sheep CRC Information Nucleus, which was set up to test leading young industry sires for an extensive range of current and novel production traits. The final validated dataset had 2,455 methane records from 2,279 animals, which were the progeny of 187 sires and 1,653 dams with 7,690 animals in the pedigree file. The protocol involved rounding up animals from pasture into a holding paddock before the first measurement on each day and then measuring in groups of up to 16 sheep over the course of the day. Methane emissions declined linearly (with different slopes for each site) with time since the sheep were drafted into the holding area. After log transformation, estimated repeatability (rpt) and heritability (h(2)) of liveweight-adjusted CH4 emissions averaged 25% and 11.7%, respectively, for a single 1-h measurement. Sire × site interactions were small and nonsignificant. Correlations between EBV for methane emissions and Sheep Genetics Australia EBV for production traits were used as approximations to genetic correlations. Apart from small positive correlations with weaning and yearling weights (r = 0.21-0.25, P < 0.05), there were no significant relationships between production trait and methane EBV (calculated from a model adjusting for liveweight by fitting separate slopes for each site). To improve accuracy, future protocols should use the mean of 2 (rpt = 39%, h(2) = 18.6%) or 3 (rpt = 48%, h(2) = 23.2%) PAC measurements. Repeat tests under different pasture conditions and time of year should also be considered, as well as protocols measuring animals directly off pasture instead of rounding them up in the morning. Reducing the time in the PAC from 1 h to 40 min would have a relatively small effect on overall accuracy and partly offset the additional time needed for more tests per animal. Field testing in PAC has the potential to provide accurate comparisons of animal and site methane emissions, with potentially lower cost/increased accuracy compared to alternatives such as SF6 tracers or open path lasers. If similar results are obtained from tests with different protocols/seasonal conditions, use of PAC measurements in a multitrait selection index with production traits could potentially reduce methane emissions from Australian sheep for the same production level.
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia NSW Department of Primary Industries, Beef Industry Centre, University of New England, Armidale, NSW 2351, Australia Dorothy.Robinson@dpi.nsw.gov.au.
authors.forename: D L
authors.initials: DL
authors.lastname: Robinson
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia NSW Department of Primary Industries, Beef Industry Centre, University of New England, Armidale, NSW 2351, Australia.
authors.forename: J P
authors.initials: JP
authors.lastname: Goopy
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia University of New England, Armidale, NSW 2351, Australia.
authors.forename: R S
authors.initials: RS
authors.lastname: Hegarty
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia NSW Department of Primary Industries, Beef Industry Centre, University of New England, Armidale, NSW 2351, Australia.
authors.forename: V H
authors.initials: VH
authors.lastname: Oddy
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia Department of Agriculture and Food of Western Australia, 3 Baron Hay Court, South Perth, WA, 6151, Australia School of Veterinary and Life Sciences, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia.
authors.forename: A N
authors.initials: AN
authors.lastname: Thompson
authors.affiliation: CSIRO Animal, Food and Health Sciences and Sustainable Agriculture Flagship, Floreat, WA 6913, Australia.
authors.forename: A F
authors.initials: AF
authors.lastname: Toovey
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia Department of Agriculture and Food of Western Australia, 3 Baron Hay Court, South Perth, WA, 6151, Australia.
authors.forename: C A
authors.initials: CA
authors.lastname: Macleay
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia Department of Agriculture and Food of Western Australia, 3 Baron Hay Court, South Perth, WA, 6151, Australia.
authors.forename: J R
authors.initials: JR
authors.lastname: Briegal
authors.affiliation: NSW Department of Primary Industries, Beef Industry Centre, University of New England, Armidale, NSW 2351, Australia.
authors.forename: R T
authors.initials: RT
authors.lastname: Woodgate
authors.affiliation: NSW Department of Primary Industries, Beef Industry Centre, University of New England, Armidale, NSW 2351, Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Donaldson
authors.affiliation: Australian Cooperative Research Centre for Sheep Industry Innovation, University of New England, Armidale, NSW 2351, Australia School of Animal Biology, Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: P E
authors.initials: PE
authors.lastname: Vercoe
mesh_terms: D000818:Animals; D001315:Australia; D004777:Environment; D005260:Female; D059647:Gene-Environment Interaction; D005838:Genotype; D060434:Herbivory / Q000502:physiology*; D008297:Male; D008697:Methane / Q000378:metabolism*; D010641:Phenotype; D012621:Seasons; D034561:Sheep, Domestic / Q000235:genetics* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D008697:Methane
keywords: enteric methane; genetic parameters; grazing ruminants; heritability; sheep