A prototype national cattle evaluation for feed intake and efficiency of Angus cattle.

Recent improvement in technologies for measuring individual feed intake has made possible the collection of data suitable for breed-wide genetic evaluation. The goals of this research were to estimate genetic parameters for components of feed efficiency and develop a prototype system for conducting a genetic evaluation of Angus cattle for feed intake. Weaning weight (WWT), postweaning BW gain (PGN), subcutaneous fat depth (SQF), and feed intake data were accumulated by the American Angus Association from a variety of cooperators and augmented with data collected for routine genetic evaluation of Angus cattle. The feed intake data were standardized (SFI, mean 0 and variance 1) within contemporary groups. Numbers of animals with observed phenotypes were 18,169, 7,107, 4,976, and 4,215 for WWT, PGN, SQF, and SFI, respectively. The 4-generation pedigree for animals with records contained 45,120 individuals. (Co) variance components were estimated with ASREML, fitting a 4-trait animal model with fixed contemporary groups for WWT, PGN, SQF, and SFI. Heritability estimates were 0.33 +/- 0.03, 0.31 +/- 0.04, 0.26 +/- 0.04, and 0.42 +/- 0.05 for direct genetic effects on WWT, PGN, SQF, and SFI, respectively. Genetic correlations of WWT and PGN with SFI were 0.40 +/- 0.07 and 0.55 +/- 0.10, respectively, and indicate their value as indicator traits in predicting EPD for feed intake. The genetic correlation of SQF and SFI was not different from 0. For all animals with a recorded feed intake phenotype, accuracy of their EPD for feed intake ranged from 0.16 to 0.64 with a mean of 0.26. However, 9,075 animals had an accuracy that was equal to or exceeded 0.2 for their feed intake EPD. Postanalysis calculation of measures of efficiency EPD was pursued. This work demonstrates the feasibility of conducting a national cattle evaluation for feed intake using indicator traits to reduce opportunity for selection bias, increase accuracy of the evaluation for a substantial number of animals, and ultimately facilitate calculation of selection indexes including feed intake.