title: Measures of methane production and their phenotypic relationships with dry matter intake, growth, and body composition traits in beef cattle.
abstract: Ruminants contribute up to 80% of greenhouse gas (GHG) emissions from livestock, and enteric methane production by ruminants is the main source of these GHG emissions. Hence, reducing enteric methane production is essential in any GHG emissions reduction strategy in livestock. Data from 2 performance-recording research herds of Angus cattle were used to evaluate a number of methane measures that target methane production (MPR) independent of feed intake and to examine their phenotypic relationships with growth and body composition. The data comprised 777 young bulls and heifers that were fed a roughage diet (ME of 9 MJ/kg DM) at 1.2 times their maintenance energy requirements and measured for MP in open circuit respiration chambers for 48 h. Methane traits evaluated included DMI during the methane measurement period, MPR, and methane yield (MY; MPR/DMI), with means (± SD) of 6.2 ± 1.4 kg/d, 187 ± 38 L/d, and 30.4 ± 3.5 L/kg, respectively. Four forms of residual MPR (RMP), which is a measure of actual minus predicted MPR, were evaluated. For the first 3 forms, predicted MPR was calculated using published equations. For the fourth (RMPR), predicted MPR was obtained by regression of MPR on DMI. Growth traits evaluated were BW at birth, weaning (200 d of age), yearling age (400 d of age), and 600 d of age, with means (± SD) of 34 ± 4.6, 238 ± 37, 357 ± 45, and 471 ± 53 kg, respectively. Body composition traits included ultrasound measures (600 d of age) of rib fat, rump fat, and eye muscle area, with means (± SD) of 3.8 ± 2.6 mm, 5.4 ± 3.8 mm, and 61 ± 7.7 cm(2), respectively. Methane production was positively correlated (r ± SE) with DMI (0.65 ± 0.02), MY (0.72 ± 0.02), the RMP traits (r from 0.65 to 0.79), the growth traits (r from 0.19 to 0.57), and the body composition traits (r from 0.13 to 0.29). Methane yield was, however, not correlated (r ± SE) with DMI (-0.02 ± 0.04) as well as the growth (r from -0.03 to 0.11) and body composition (r from 0.01 to 0.06) traits. All the RMP traits were strongly correlated to MY (r from 0.82 to 0.95). These results indicate that reducing MPR per se can have a negative impact on growth and body composition of cattle. Reducing MY, however, will likely have the effect of reducing MPR without impacting productivity. Where a ratio trait is undesirable, as in animal breeding, any of the RMP traits can be used instead of MY. However, where independence from DMI is desired, RMPR should be a trait worth considering.
authors.affiliation: NSW Department of Primary Industries, Beef Industry Centre, Armidale, NSW 2351, Australia.
authors.forename: R M
authors.initials: RM
authors.lastname: Herd
authors.affiliation: NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW 2568, Australia paul.arthur@dpi.nsw.gov.au.
authors.forename: P F
authors.initials: PF
authors.lastname: Arthur
authors.affiliation: NSW Department of Primary Industries, Agricultural Research Centre, Trangie, NSW 2823, Australia.
authors.forename: K A
authors.initials: KA
authors.lastname: Donoghue
authors.affiliation: NSW Department of Primary Industries, Beef Industry Centre, Armidale, NSW 2351, Australia.
authors.forename: S H
authors.initials: SH
authors.lastname: Bird
authors.affiliation: NSW Department of Primary Industries, Agricultural Research Centre, Trangie, NSW 2823, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Bird-Gardiner
authors.affiliation: University of New England, Environment and Rural Science, Armidale, NSW 2351, Australia.
authors.forename: R S
authors.initials: RS
authors.lastname: Hegarty
mesh_terms: D000375:Aging / Q000378:metabolism; D000821:Animal Feed; D000818:Animals; D001823:Body Composition / Q000502:physiology*; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D004435:Eating / Q000502:physiology; D005260:Female; D017752:Greenhouse Effect; D008297:Male; D008697:Methane / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging; D010641:Phenotype; D012137:Respiratory System / Q000378:metabolism; D014463:Ultrasonography
chemical_list: D008697:Methane
keywords: cattle; greenhouse gas; methane; respiration chamber