CT scan archive adds to methane emission data

Rumen measurements taken from CT scans can be used to predict methane emissions, studies by Scotland’s Rural College (SRUC) have shown.

Sheep genetics researcher Dr Nicola Lambe said scans had not only shown large differences between breeds, but also within breeds.

Nicola’s work built on previous research that showed rumen size, not shape, affects methane yield. The bigger the rumen, the more methane is produced.

See also: 40-50% difference in lamb methane emissions, project shows

She delved into the SRUC’s CT archive (CT scanning is routine for elite UK terminal sire sheep), to investigate the variation in rumen volume between, and within, breeds.

Breed differences

A data set of 220 Scottish Blackface and Texel lambs, which had been reared together on grass from birth to slaughter, showed big differences in volumes between the two breeds.

When adjusted for age, rumen volume was 16% higher in the Scottish Blackface lambs – when adjusted for liveweight, the difference rose to 26%.

Another study of CT archives showed significant differences between Charollais, Hampshire Down, Meatlinc, Suffolk and Texel sires, of between 10% and 23%, at the same age or liveweight.

A further data set from 649 commercial Texel ram lambs revealed that rumen volume was moderately heritable (0.45), highlighting the potential for genetic selection within-breed.

Further research

When considering the relationship between rumen volume and wider economic or environmental traits, Nicola said that generally, lower estimated breeding values for fat, muscle and muscularity traits are associated with higher rumen volume.

In addition, a larger rumen is needed to process diets with higher fibre.

“Further research is needed into the complex relationships between rumen function, methane emissions, feed efficiency, production and resilience across different types of sheep systems,” she said.

Rumen volume is among the measurements being taken in Breed for CH4nge, an Innovate UK project involving 13,000-14,000 sheep.

The aim is to build up data sets to explore genetic correlations between rumen volume and methane measured by portable accumulated chambers, and rumen volume and feed efficiency, in UK maternal breeds, said Nicola.

Further data sets are being collected via Teagasc and Farming Connect. In addition, artificial intelligence is being used to predict rumen volume from CT scans, with good success, she added.

Dr Nicola Lambe was speaking at the recent Sheep Breeders Round Table 2024, held near Derby.