|COLE, JOHN - Former ARS Employee|
|PARKER GADDIS, KRISTEN - Council On Dairy Cattle Breeding|
|TEMPELMAN, ROBERT - Michigan State University|
Submitted to: AIPL Research Reports
Publication Type: Government Publication
Publication Acceptance Date: 5/7/2021
Publication Date: 5/7/2021
Citation: Van Raden, P.M., Cole, J.B., Neupane, M., Toghiani, S., Parker Gaddis, K.L., Tempelman, R.J. 2021. Net merit as a measure of lifetime profit: 2021 revision. AIPL Research Reports. NM$8(05-21).
Technical Abstract: The lifetime net merit (NM$) index ranks dairy animals based on their combined genetic merit for economically important traits. Indexes are updated periodically to include new traits and to reflect prices expected in the next few years. The August 2021 update of NM$ includes new genetic evaluations for feed saved, heifer livability, and earlier first calving. Feed saved is reported in pounds per lactation and includes the reduced feed for maintenance as a function of body weight composite and the residual feed intake measuring differences of intake expected from production and body weight vs. actual intake. The new estimate of cow maintenance is much larger than previously assumed, causing more selection for smaller cow size. Relative emphasis on most other traits was slightly less because of the addition of the new traits, and economic values of all traits were revised. Selection goals are now displayed as relative emphasis calculated from the economic values and standard deviations of evaluations rather than standard deviations of true transmitting abilities, thus better reflecting progress expected given differing reliabilities of the traits. Feed intake is currently recorded and evaluated only for Holsteins. The 2021 and 2018 NM$ indexes were correlated by 0.981 for recently proven Holstein bulls. Cows with genes that that result in better feed efficiency, heifer livability, and earlier calving are more profitable than cows that lack those traits. An increase in genetic progress worth $10 million/year is expected on a national basis, assuming that all of the changes are improvements and that all breeders select on NM$.