Rumen Differences between Sheep Identified as being Low or High Methane Emitters

Abstract Text:

Divergent selection lines of sheep for methane emissions have been established. The top and bottom 10% of ewes, (gCH₄/kgDMI) screened for this trait, were computer tomography scanned (24 high and 21 low emitters). The following rumen compartments; reticulum, rumen and atrium, ventral sac of rumen (rostral), dorsal sac of rumen and ventral sac of rumen (caudal) were measured for volume, and surface area. Rumen composition (gas, raft, liquid) volume and weight were also measured. Data were analysed using R, and parsimonious models selected for different variables. Measurements between the two groups differed with high methane emitters having greater total rumen surface area (12%), total rumen volume (20%), and total rumen raft volume and weight of rumen contents (27%, 28% respectively). Results suggest that differences in CH₄ yield between low and high CH₄ emission sheep arise from morphological differences of their reticulo-rumen.

Keywords:

Sheep

Methane

Computer tomography

Rumen morphology