Table 5.

Accuracy of selection indices to improve breeding objectives for feed efficiency

Breeding objectivea	Gain traits in indexa,b	Objective accuracyc
		0.25	0.5	0.75	1.00
FGSd (ADG83 − 0.166 DMI83)	ADG42	0.209 (0.003)e	0.430 (0.010)	0.667 (0.009)	0.96
	PADG	0.190 (0.005)	0.393 (0.011)	0.608 (0.005)	0.84
	ADG42, PADG	0.216 (0.003)	0.445 (0.008)	0.687 (0.005)	0.96
FGH (ADG83 − 0.115 DMI83)	ADG42	0.181 (0.005)	0.383 (0.015)	0.635 (0.015)	0.95
	PADG	0.175 (0.013)	0.357 (0.025)	0.557 (0.008)	0.75
	ADG42, PADG	0.210 (0.004)	0.429 (0.009)	0.673 (0.007)	0.95
RG (ADG83 − 0.089 DMI83)	ADG42	0.171 (0.006)	0.365 (0.016)	0.629 (0.017)	0.94
	PADG	0.181 (0.018)	0.362 (0.027)	0.552 (0.005)	0.72
	ADG42, PADG	0.212 (0.005)	0.431 (0.008)	0.674 (0.008)	0.94
RFI (ADG83 − 0.228 DMI83)	ADG42	0.224 (0.002)	0.457 (0.006)	0.697 (0.004)	0.98
	PADG	0.208 (0.003)	0.428 (0.007)	0.656 (0.004)	0.91
	ADG42, PADG	0.226 (0.002)	0.461 (0.006)	0.703 (0.003)	0.98

^aADG83 and DMI83 were ADG (kg/d) and DMI (kg/d), respectively, over the entire test period, which averaged 83 d; ADG42 and DMI42 were ADG (kg/d) and DMI (kg/d), respectively, over the first 42 d of test period; PADG was postweaning ADG (kg/d).

^bAll indices included DMI42 as the measure of DMI.

^cIndex accuracies were summarized from data points within ± 0.05 of the stated objective accuracy after adjusting for the slope of the trend line relative to objective accuracy within that interval.

^dThe objective functions were FGS and FGH; RG; and RFI.

^eMean (SD) index accuracy after adjusting for variation in objective accuracy of the animals summarized.