Sustainability & efficiency

Effects of selection weight and phenotyping intensity of enteric methane emission in national sheep breeding objectives

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Abstract

Enteric methane emission (CH4) from ruminant livestock is a significant contributor to global greenhouse gas emissions. This study aimed to evaluate long-term genetic responses to including CH4 in the national sheep breeding goal with varying weights in the Total Merit Index (TMI) and levels of CH4 phenotyping on ewes per year. To realize this objective a digital twin fully mimicking the Norwegian White Sheep breeding scheme that selects for 12 growth and fleece, carcass, and maternal traits, was developed using the Julia package xyBnG.jl. Ten alternative scenarios with four selection weights for CH4 (0%, 2%, 5%, and 10%) and four annual numbers of ewe CH4 phenotypes (0, 2K, 4K, and 6K) added to the genomic prediction, were simulated for 12 years. Every year 120K lambs were born under ram circle mating system conditions, and each scenario was replicated 20 times. Results showed that incorporating CH4 in the breeding objective reduced methane emission corrected for live weight while increasing carcass and fleece weight. The most aggressive scenario that weighted 10% on CH4 and phenotyped 6K ewes presented an emission reduction of 0.032g CH4 per hour over 12 years, i.e., 5.5 generations. In general, larger selection weight and phenotyping intensity contributed to more efficient selection for low CH4. These results indicate that sheep breeding strategies for reduced ME and improved production can be combined, to reduce the methane intensity. However, achieving substantial genetic reduction for CH4 depends strongly on the weight in TMI and the number of phenotypes available for genomic prediction. Strategic investment will be essential for selection for more sustainable, low emission sheep production.

Keywords: 2026

How to Cite:

Aspeholen, B., Berg, P., Cao, L., Difford, G., Jakobsen, J. & Yu, X., (2026) “Effects of selection weight and phenotyping intensity of enteric methane emission in national sheep breeding objectives”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2283839. doi: https://doi.org/10.31274/wcgalp.23521

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