What have we learnt about breeding sheep for lower methane? – understanding the biology

blog by Dr Nicola Lambe, SRUC

The Challenge

In our quest to breed sheep to reduce the flock carbon footprint, whilst maintaining production, we need to understand why sheep vary in their methane output and how we can use that information to design breeding programmes to deliver those win-wins. We used the maternal breeds within the Innovis nucleus flock to investigate relationships of methane emissions with feed efficiency, rumen volume and gut microbiome to understand the biology behind variation in methane output.

Main findings

We found more variation within breed than between breeds for feed efficiency, with the most efficient 25% of lambs eating over 20% less feed (0.3kg DMI) per day, but growing at the same rate, as the least efficient 25% of lambs. Daily feed intake and feed efficiency (adjusted for weight and growth) were highly heritable, but were not related to methane output – at the phenotypic or genetic level. Using CT scanning of lambs, rumen volume was shown to be variable and heritable and there was a genetic relationship between lower methane (g/day) and smaller rumens. However, there was no significant genetic relationship of rumen volume with feed intake or feed efficiency. Preliminary analysis of rumen samples collected from grazing lambs, immediately after PAC measurements, looked at number and abundance of rumen micro-organisms which explained two-thirds or more of the variation in methane (g/day). These results reinforce the need to balance selection for methane and productivity in a breeding programme.