Submitted to: Hoard's Dairyman
Publication Type: Popular Publication
Publication Acceptance Date: August 4, 2003
Publication Date: N/A
With the August 2003 USDA genetic evaluations, the net merit (NM$) index was revised to incorporate cow fertility (daughter pregnancy rate) and calving ease (daughter and service sire) traits and to update economic values for the other traits (milk, fat, protein, productive life, somatic cell score, udder composite, feet-and-legs composite, and body size composite). The new NM$ index (NM$ 2003) is defined as the expected lifetime profit as compared with the breed base cows born in 1995. Under the previous NM$ index (NM$ 2000), 62% of the emphasis was on yield traits; for NM$ 2003, only 55% of the emphasis is placed on yield traits, with correspondingly more emphasis placed on selected fitness traits. The correlation between the previous NM$ (NM$ 2000) and the new NM$ (NM$ 2003) is .98, which means that the revised index will cause only small changes in the rankings for most bulls. Extreme bulls (either good or bad) for daughter pregnancy rate, service sire calving ease, or daughter calving ease are more likely to have their rankings change appreciably. About 10% less annual genetic progress will be made for yield traits under NM$ 2003 than under NM$ 2000. However, the expected genetic change per decade is still +2380 pounds for milk, +96 pounds for fat, and +78 pounds for protein. The slightly lower progress for yield traits is offset by much greater progress for fitness traits.