Animals in the dataset were from 7 New Zealand Sheep Improvement Limited (SIL) flocks including 1 AgResearch flock (SIL flock number 2638), 3 Central Progeny Test (CPT) flocks (SIL flock numbers 4640, 4757, 9153), 2 industry flocks (SIL flock numbers 2629, 4474), and the “methane yield selection” flock (SIL flock number 3633). In total, 3601 lambs were measured at least once using PAC or RC of which 2,255 lambs (born between 2012 and 2015; at 7 ± 3 [±StDev; range 4 to 13] mo of age) had 4,733 separate 1-h measurement records using PAC and 2,110 lambs (born in 2007 and between 2009 and 2015; at 9 ± 2 [range 6 to 12] mo of age) had 8,655 daily records using RC. Of these, 844 animals had both PAC and RC measurements as lambs. In addition, 1,251 (2,387 records) animals were measured in PAC as yearling/ewes (called ewe in this paper from this point onwards; 42 ± 19 [range 16 to 88] mo of age) of which 874 animals also had RC measurements as lambs and 698 had PAC measurements as lambs. Flock, birth year, sex, and measurement year and season are detailed in Supplementary Table S1 .
“Methane yield selection” flock animals (Pinares-Patiño et al., 2013 ) were progeny of maternal dual-purpose sires generated by the New Zealand industry CPT program (McLean et al., 2006 ), comprising Coopworth, Romney, Perendale, Texel, and composite breeds, where the latter breed consisted primarily of combinations of the former breeds with additional infusions of Finn and East Friesian. All rams were mated to composite ewes. Ewe progeny born in 2007 and between 2009 and 2011 (and also ram lambs born in 2009) was measured for CH4 emissions per unit of feed DMI (i.e., CH4 yield) (Pinares-Patiño et al., 2013 ), with the most extreme low and high 10% retained for further breeding. The lines were closed in 2012 and all sires used from 2012 onwards were born in the high and low CH4-yield selection flocks, which are currently maintained at 100 ewes per line. Progeny from the CH4-yield selection flock included in the dataset was born between 2010 and 2015.
“Methane yield selection” flock animals (Pinares-Patiño et al., 2013 ) were progeny of maternal dual-purpose sires generated by the New Zealand industry CPT program (McLean et al., 2006 ), comprising Coopworth, Romney, Perendale, Texel, and composite breeds, where the latter breed consisted primarily of combinations of the former breeds with additional infusions of Finn and East Friesian. All rams were mated to composite ewes. Ewe progeny born in 2007 and between 2009 and 2011 (and also ram lambs born in 2009) was measured for CH4 emissions per unit of feed DMI (i.e., CH4 yield) (Pinares-Patiño et al., 2013 ), with the most extreme low and high 10% retained for further breeding. The lines were closed in 2012 and all sires used from 2012 onwards were born in the high and low CH4-yield selection flocks, which are currently maintained at 100 ewes per line. Progeny from the CH4-yield selection flock included in the dataset was born between 2010 and 2015.
