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Aspects of digestive function in sheep related to phenotypic variation in methane emissions.
Abstract. Ruminant livestock contribute to atmospheric methane (CH4) from enteric microbial fermentation of feed in the reticulo-rumen. Our research aimed to increase understanding of how digestive characteristics and rumen anatomy of the host animal contribute to variation in CH4 emissions between sheep. A total of 64 ewes were used in an incomplete block experiment with 4 experimental test periods (blocks). Ewes were chosen to represent the diversity of phenotypic variation in CH4 emissions: there were at least 10 offspring from each of 4 sires and a range of liveweights. Throughout the experiment the ewes were fed equal parts of lucerne and oaten chaff, twice daily, at 1.5 times maintenance requirements. Daily CH4 emission (g/d) increased significantly (P< 0.001) with increasing dry matter intake (DMI) and reticulo-rumen volume (P< 0.001). Lower methane yield (MY: g CH4 /kg DMI) was associated with shorter mean retention times (MRT) of liquid (r = 0.59; P< 0.05) and particle phases (r = 0.63; P< 0.05) of the digesta in the rumen. Significant between-sire variation was observed in CH4 emissions and in rumen volume (P = 0.02), the masses of liquids (P = 0.009) and particles (P < 0.03) in the rumen and the proportion of gas in the dorsal sac of the rumen (P = 0.008). The best predictors of variation in CH4 emissions due to the host were DMI, CO2 emissions, rumen volume, liveweight, MRT of particles in the rumen, dorsal papillae density and the proportion of liquid in the contents of the rumen compartments.
AN17141 Accepted 23 August 2017
© CSIRO 2017