Predicted transmitting abilities (PTAs) for residual feed intake (RFI) were computed using data from 4,823 feed intake trials of 3,965 U.S. Holsteins born 1999 to 2013 in 9 research herds. The RFI averages were already adjusted to remove phenotypic correlations with milk energy output, metabolic body weight and body weight change and for several environmental effects, including other nutrition experiments during the feed intake trials. Traditional PTAs for RFI of 74 million Holsteins were then estimated by an animal model that also included effects for age-parity group, trial date, herd management group, permanent environment, herd-sire interaction and regressions on inbreeding and on genomic evaluations for milk energy and body weight composite (BWC). The milk energy and BWC terms were included to remove positive genetic correlations that remained after phenotypic correlations were removed. Estimated heritability was 0.14; repeatability across lactations was 0.24. Genomic PTAs for RFI included 60,671 genetic markers for 1.6 million Holsteins; genomic reliabilities calculated for elite young animals averaged 12% compared with 3% for traditional reliabilities. Economic value of RFI is very large, and RFI could receive 16% of total emphasis in the net merit index; however, its low reliability will limit extra genetic progress to about 1% more than current progress. One option for publishing the trait is to combine the benefits from reduced RFI and smaller BWC into feed saved per lactation. Additional records could make feed intake an important trait in future selection indexes for dairy cattle. Keywords: feed efficiency, residual feed intake, genomic evaluation, selection index

Paul VanRaden, Jeff O'Connell, Erin Connor, Mike VandeHaar, Rob Tempelman, Kent Weigel

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Feed Intake and Efficiency 1, , 125, 2018
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