Table 1.

Trait definitions

Trait name	Abbreviation	Unit	Definition
Methane	CH4	g/day	Methane in grams emitted per day, based on an individual GEM system measurement. Animals can have multiple records per day.
Carbon dioxide	CO2	g/day	Carbon dioxide in grams emitted per day, based on an individual GEM system measurement. Animals can have multiple records per day.
Dry matter intake	DMI	kg/day	Dry matter intake in kilograms per individual day during methane measurement.
Live weight	LW	kg/day	Kilograms of liveweight on a specific day during the test period.
Eye muscle area	EMA	mm	Millimeter measurement at single deepest point of the eye muscle at the third lumbar vertebra on top of the loin.
Fat depth	FD	mm	Millimeter measurement average of all fat depths recorded at the third lumbar vertebrae and at the 13th thoracic rib.
Intramuscular fat	IMF	%	Percentage estimated from images taken at a lateral position to the animal’s spine at the 13th thoracic rib.
Carcass weight	CW	kg	Kilograms of dressed carcass, weighed 2 h post slaughter.
Carcass conformation	CC	15-point scale	EUROP classes subdivided into three categories, resulting in a 15-point scale.
Carcass fat	CF	15-point scale	Scale from 1 to 15, where 1 represents the least level of fat cover and 15 represents the greatest level of fat cover.
Methane yield	MY	g/kg	Ratio trait of methane in grams divided by kilograms of dry matter intake per day.
Methane intensity (liveweight)	MIL	g/kg	Ratio trait of methane in grams divided by kilograms of liveweight.
Methane intensity (carcass weight)	MIC	g/kg	Ratio trait of methane in grams divided by kilograms of carcass weight.
Residual methane	RCH4	g/day	Methane adjusted for dry matter intake and live weight.