Sustainability & efficiency

Is eating less better? Relationship of feed efficiency with production traits in New Zealand sheep

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Abstract

Sustain Sheep is an international collaboration between Ireland (TEAGASC and ICBF), UK (SRUC), New Zealand (BSI - AgResearch), France (INRAE), Norway (NSG and NMBU) and Uruguay (INIA) with the objective of assessing the impact of reducing global sheep methane emissions. The aim of this project is to begin to understand the impact of selection for residual feed intake in young female sheep on enteric methane emissions and lifetime production traits. Residual feed intake (RFI) is an estimate of whether an animal is consuming more or less energy for its biological outcomes than predicted. RFI is a moderately heritable trait that is important as feed represents the greatest production cost and significantly impacts environmental sustainability. Traditionally measured in growing males, this study uniquely measured RFI in growing females, ranked them, and tracked these animals through multiple lambing's to assess impacts on lifetime production traits and breeding objectives.This study analysed data from 1,549 ewes lambs from four New Zealand sheep flocks born between 2014-2021 that were measured in a feed intake facility to calculate RFI and RFI breeding values (BV). Correlations between the RFI BV and 23 other industry-relevant BVs were investigated. The top and bottom 10% within eleven measurement groups (flock within year) were selected based on RFI BVs and analysed for significant differences using Student's t-tests (pThe main differences between the RFI extremes were for carcass yield and methane traits. Four traits showed the most significant differences: shoulder lean yield BV (SHLYBV), methane production BV (PACCH4BV), lean yield BV (LEANYBV), and hind-quarter lean yield BV (HQLYBV), each with three of eleven groups statistically different. Effect sizes ranged from medium to very large: SHLYBV (Cohen's d=0.908 to 1.529), PACCH4BV (Cohen's d=-0.781 to -1.103), LEANYBV (Cohen's d=0.948 to 1.464), and HQLYBV (Cohen's d=-0.8 to 1.812). We also compared the groups for selection indices for maternal traits (MW). Four groups differed significantly for MW + meat with medium to very large effects (Cohen's d=-1.287 to 2.10). Three groups differed for MW + wool + meat + FEC + Dags with medium to very large effects (Cohen's d=-0.779 to 2.427) and three groups differed significantly for a dual purpose Maternal and terminal index with large to very large effects (Cohen's d=-1.22 to -0.858), respectively.Results indicate meaningful differences between top and bottom 10% RFI BV groups for methane, meat yield and profit, suggesting RFI-based selection may impact other selected traits. Directional effects, however, varied between groups, suggesting increased sample sizes are required to clarify these relationships. Future work will focus on determining genetic correlations between RFI, methane, and lifetime production traits to assess the effects of selecting for RFI and methane on important lifetime characteristics.

Keywords: 2026

How to Cite:

Bilton, T., Clarke, R., Johnson, P., Knowler, K. & Rowe, S., (2026) “Is eating less better? Relationship of feed efficiency with production traits in New Zealand sheep”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286222. doi: https://doi.org/10.31274/wcgalp.23882

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