Sustainability & efficiency

Genetic relationship between methane emissions and rumen volume in sheep

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Abstract

Increased volume of the reticulum and rumen (RRvol) of sheep, measured by computed tomography (CT) scanning, has been associated with increased methane emissions. Significant RRvol differences have been identified between sheep lines divergently selected for methane emissions (1,2), between different breeds, or sires within breed (4), whilst RRvol is moderately heritable within breed (4). Sheep often graze extensive, marginal land and RRvol may affect their ability to digest poor-quality vegetation. The objective of this work was to estimate the genetic relationship between RRvol and methane emissions, across a data set spanning different countries, sheep breeds and production systems. Data were combined across 4 research projects from flocks in Scotland, England, Wales and Ireland. All had data recorded on RRvol, as measured using the same mobile CT scanner (4), and methane (CH4) and carbon dioxide (CO2) emissions measured using portable accumulation chambers (PAC), calculating emissions as g/d, rescaled to lot and population means (3). Three similar PAC units (AgResearch, New Zealand) collected data across the projects, using shared protocols. PAC data were available from 5451 sheep, of which, 2056 had duplicate measurements (~2 weeks apart) and 2013 also had RRvol measurements. RRvol was available on another 1078 closely-related sheep with no PAC measurements. Data were included from 18 breeds/crossbreeds, including hill, lowland-maternal and terminal-sire breeds, typical of UK and Irish sheep systems. The combined pedigree file included 747,495 animals (16,437 sires; 151,210 dams). Average age at PAC was 275d (range 108-1401) and at CT was 262d (range 110-629), with average live weights of 44kg (range 13-96) and 40kg (range 17-79), respectively. Univariate and bivariate analyses in ASReml (Version 4.2) for RRvol, CH4 and CO2, fitted animal models including fixed effects of live weight and age at time of measurement, breed, sex, litter size during rearing, dam age (years), flock x year interaction. A permanent environmental effect, to account for duplicate PAC measurements, was non-significant, so dropped from models. Univariate heritabilities (s.e.) were 0.20 (0.05) for RRvol, 0.08 (0.02) for CH4 and 0.22 (0.02) for CO2. A high positive genetic correlation (0.7) was estimated between RRvol and CH4 and a low positive phenotypic correlation (0.1) (Table 1). Correlations of RRvol with CO2 were not significantly different from zero. In conclusion, reticulo-rumen volume is strongly genetically correlated with methane emissions. This could provide opportunity for CT to predict methane emissions within breeding programmes, but should be considered in breeding programme design to avoid detrimental effects on other important traits linked to system resilience. References1Bain W.E. et al. (2014) Proc.10th WCGALP. p.039 2Goopy J.P. et al. (2014) Br.J.Nutr. 111:578-585. https://doi.org/10.1017/S00071145130029363Jonker A. et al. (2020) Ministry for Primary Industries, NZ, pp.55-62. https://www.mpi.govt.nz/resources-and-forms/publications/4Lambe N.R. et al. (2022) Anim.Prod.Sci. 62(7):610-621. https://doi.org/10.1071/AN21423

Keywords: 2026

How to Cite:

Dods, E., Kaseja, K., Lambe, N., McGovern, F., McHugh, N., McLaren, A. & Roden, J., (2026) “Genetic relationship between methane emissions and rumen volume in sheep”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285395. doi: https://doi.org/10.31274/wcgalp.23680

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