Reducing methane emissions by including methane production or feed intake in genetic selection programmes for Suffolk sheep

The use of selective breeding to reduce methane (CH4) emissions is an option for reducing carbon emissions from livestock farming systems. The current study models UK lowland terminal sire (meat) sheep production systems to study the impacts of including CH4 emissions and/or feed intake as breeding objective and selection criteria traits in sheep breeding systems, on the predicted genetic responses of production traits. Nine breeding goal traits and 15 selection index traits were modelled in a Suffolk breeding flock with a deterministic model of trait economic values (EVs). Methane was given an EV equivalent to a carbon price varying from £0 to £538/t CO2-e. When currently used selection indices added feed intake as a breeding objective, CH4 reductions of 0·15 and 0·05 kg CO2-e/sheep/year were predicted when intake was, or was not, measured, respectively, with a zero carbon price. These reductions were relatively insensitive to carbon price. Overall economic (index) response to selection was insensitive to carbon price and increased with higher feed costs, when neither CH4 nor feed intake was measured. When CH4 and/or intake were measured, overall economic responses increased with higher carbon prices, when feed costs were zero. Methane and intake responses were only sensitive to carbon price (whether CH4 and intake were measured or not) when feed costs were zero. To achieve a desired reduction of 0·1 kg CH4/head/year (cumulative 30% reduction in 20 years) when feed costs were zero, CH4 and/or intake needed to be measured. If CH4 was measured, carbon price needed to be >£50/t CO2-e; if intake was measured carbon price needed to be >£100/t CO2-e. Including feed intake as a breeding objective trait with non-zero feed costs should assist in reducing CH4 in breeding programmes. Selective breeding of terminal sheep by index selection has the potential to contribute a reduction of up to 0·27 kg CO2-e per ewe per annum, depending on the traits measured, feed costs and carbon price. This would help meet the UK Government's greenhouse gas reduction targets for farming systems.