Sustainability & efficiency

Diurnal patterns of methane and carbon dioxide emissions associated with breeding sheep for divergent methane yield

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Abstract

Unique sheep selection lines selectively bred for divergent methane (CH4) yield for two decades have pioneered livestock methane research. These lines have provided evidence that breeding for low methane animals is a viable mitigation tool without negatively impacting health or production, demonstrating that animal breeding can achieve substantial gains in lowering greenhouse gas emissions from livestock. Globally the development of livestock breeding schemes for lowered enteric emissions is now widespread. Recent development of tools and techniques for rapid measurement of gas emissions from ruminant livestock involve brief sampling to predict daily and ultimately lifetime emissions. This requires an understanding of the diurnal pattern of methane production from the rumen. The aim of this study was to i) validate via respiration chambers that selecting for two generations using rapid measures has continued divergence of the two lines and ii) determine whether the diurnal pattern of CH4 and carbon dioxide (CO2) emissions differs between the two methane lines. CH4 and CO2 emissions were measured on 96 ram lambs (born in the 14th breeding season of the flock) using respiration chambers across two periods approximately 2 weeks apart, when fed a diet of lucerne pellets at 2x maintenance energy requirements. Approximately 6-minute measures were obtained across two days in each period from which the daily CH4 and CO2 emissions (g/day) were estimated. A difference of 24% for CH4 emissions (g/day) and CH4 yield (g/kg DMI) was observed between the low and high methane lines (P2 emissions (P=0.550) and dry matter intake (P=0.717). Furthermore, the difference in gas emissions between the lines was relatively consistent for CH4 during the 24 h measurements but varied for CO2 with animals from the low methane line having higher CO2 immediately after feeding but lower CO2 >8 h after feeding compared to the high methane line. These changes in the diurnal CO2 emissions suggest that breeding for divergent methane yield has changed the metabolism of the animal or feed degradation and passage kinetics of the rumen. Furthermore, these results highlight some potential challenges with the generation of CO2 breeding values or using CO2 as a proxy for feed intake from short-term measures (i.e., portable accumulation chambers, sniffers).

Keywords: 2026

How to Cite:

Bilton, T., Booker, F., Dobson-Hill, B., Hickey, S., Jonker, A., McEwan, J. & Rowe, S., (2026) “Diurnal patterns of methane and carbon dioxide emissions associated with breeding sheep for divergent methane yield”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285303. doi: https://doi.org/10.31274/wcgalp.23645

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